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Tuberculosis mortality in the negro population of Antigua, British West Indies, over the last hundred years
444
Tubercle, Lond., (1961), 42, 444
TUBERCULOSIS MORTALITY IN THE NEGRO POPULATION OF ANTIGUA, BRITISH WEST INDIES, OVER THE LAST HUNDRED YEARS by K. H.
UTTLEY
Medical Department, St. John's, Antigua, West Indies SUMMARY
An investigation of death records since 1857 has been carried out in Antigua, West Indies, to find out the mortality from tuberculosis over the century in the negro inhabitants. The island is favourably placed for such a survey, because censuses have been taken at frequent intervals, births and deaths registration and the recording of the cause of death have been good over the period in question, and it has been possible to separate the records of those of African descent from those of other races. The population is an agricultural one, self-contained, whose numbers fluctuated between 29,000 and 54,000. The crude death rate from the disease at the beginning of the hundred years was 4·6 per 1,000; it fell to 0·46 in 1947-56. Standardised against the England and Wales population of 1901 the corresponding figures were 4·66 and 0·48. The fall in mortality was uniform except for one decade of severe droughts and economic depression. For the last thirty years the mortality has been roughly the same as that of the United Kingdom. In the mid-nineteenth century tuberculosis accounted for 11 % of all deaths; a century later the percentage was 4. Over the whole century the variations in the sex ratio of all tuberculosis deaths were not statistically significant, but at times there have been considerable differences between the sex ratio of the disease at different ages. The mortality curves at ages for each sex show a material fall with each succeeding decade of the century. A study of cohort mortality curves in Antigua shows more similarities with corresponding curves in England and Wales than might have been expected in a tropical locality. It is also possible to infer from these curves that a likely cause of the mid-nineteenth century epidemic of tuberculosis in the island was the freeing of the slaves in 1834, who went straight from the isolation of relatively healthy estate life to the congestion of crowded and unhygienic villages. The evidence of the negro tuberculosis mortality in Antigua suggests that perhaps too much emphasis may have been placed in the past on race as being a major factor in influencing mortality rather than on elements in the environment.
Antigua is a small island of 108 square miles in area. It is one of the Leeward Islands, which lie between Puerto Rico on the west, and the Windward Islands, Martinique and Barbados to the south-east. Except for the southwestern third of the island, with hills rising to 1,330 feet, it consists of undulating plains and low hills. The trade winds can blow freely over its whole extent and there is not the hot muggy weather so frequently met with in the neighbouring mountainous islands. This has a corresponding disadvantage in that the lack of high hills and their cloud cap result
TUBERCULOSIS IN ANTIGUA
445
in a low rainfall of 45 to 50 inches a year, half of which occurs between August and December. Variations in the amount of annual rainfall are considerable and the island is subject to long periods of severe drought every few years. Temperatures are equable and it is unusual to have a variation of more than ten degrees from the annual mean of 79° F. The people are mostly of African descent, with perhaps 10% of mixed blood; during the period under review the white population was never more than 5 % of the total and was usually much less. There has never been any East Indian population. The Antiguans are engaged in agriculture. About 22 % live in the only town; the remainder live in forty small compact villages of 200 to 1,500 inhabitants, grouped evenly over the island. The town, with 12,000 residents, has wide streets, with few narrow alleyways; most buildings have only one floor, the houses and huts are spaced away from each other; the town extends along a harbour, and although there is a small area of slum no point in the town is more than 600 yards from open country. Most of the houses of the island, whether in town or country, consist of small huts of under 200 square feet in area. They stand in their own little yards, surrounded by collections of rubbish, old cans, bottles, boxes and household refuse. At nights the windows and doors are kept tightly shut to exclude the 'spirits'. Such an arrangement is an excellent one for the familial spread of tuberculosis, which is the main manner of spread of that disease in Antigua, but apart from this, the isolation of the house reduces the risk for outsiders (Gilmour, 1944). The family lives out of doors for sixteen hours out of the twenty four, and the sunshine and space make contact at that time much less than it would be in colder climates. Although village houses are dirty and surrounded by refuse, there has not been the squalor and congestion that have prevailed in the cities and towns of Europe and North America. A large proportion of the women work in the fields for much of the year, whether or not they are pregnant ornursing, There is a season of the year after the sugar cane has been cut, from August to December, when there is unemployment among the men. No records of unemployment are kept, but in years of drought it must be extensive. The diet has always been an unbalanced one, with an undue predominance of carbohydrates. A porridge of powdered Indian corn, (maize.) is the staple source of energy; in the cane-cutting season from January to July, this is supplemented by chewing considerable amounts of sugar cane stems. Meat and milk products have always been very deficient in the diet, and it is only in the last decade that attention has been given to any great extent to the catching of fish. For months at a time vegetables are not available or are beyond the reach of the poor, but as regards fruit, mangoes are an important article for two months of the year. The little milk that is drunk is always consumed boiled, for climatic reasons. A hundred years ago the population was 36,000; it fell slowly to 28,800 in 1921, but has risen rapidly since the early thirties owing to the great fall in the infant death rate, and in 1956 it was 54,200. There has been a certain amount of emigration at times of unemployment, mostly of young men; at the beginning of the century many went to the Panama Canal Zone to work on the construction of the Canal; on other occasions they have emigrated to the United States, and at present they are going to the United Kingdom. All the same, the population is a self-contained one and had little contact with the outside world in the earlier part of the period under review. At censuses 5 % to 10% of the population claimed to have been born outside the Colony. Since 1856 there have been eight censuses: in 1861, 1871, 1881, 1891 1901 (total for the sexes only), 1911, 1921 and 1946. Probably a certain proportion of the very young escaped enumeration at the earlier censuses; apart from this it is likely that the totals for each sex were fairly accurate, but there are bound to be many errors as regards stated age when one is dealing with uneducated, rural tropical communities, where people frequently have little idea of their correct ages. There has been a considerable preponderance of females over males in all the age groups beyond early childhood. Associated with a male/female live birth ratio of 1030, which is much lower than that
446
TUBERCLE
for England and Wales, is the fact that the ratio ofthe sexes at ages of 15 years and over is 754 males to 1,000 females, a ratio that has not varied much from one decade to another. Births and deaths registration, introduced and made compulsory in 1856, became reasonably accurate in the course of a decade. Factors influencing this accuracy were: 1. There were sufficient physicians throughout the period who had been trained in the British Isles or in Canada; 2. The island is a small one and has good communications; 3. A series of ordinances culminated in that of 1880 by which a midwifery service was established; insofar as numbers of midwives are concerned, this was in my opinion more than enough to handle all births - there was one midwife to 1,200 inhabitants; 4. As regards the burial of the dead, no dead body could be buried without a burial order, which in turn could not be supplied without the production of a physician's or coroner's certificate of the cause of death. The accuracy of death returns, vary from country to country, so that it is likely that among the international comparisons which I have made there may be some that are invalid; but in this matter I would like to quote Wilcocks (1932) who wrote: 'It should not be overlooked that observers of long ago were no more lacking in clinical acumen than (present day) men who have so many more advantages'. In Antigua, as in the tropics generally, the mortality from tuberculosis may be considered an 'index pointing to the conditions of life and work prevailing in the region' (Crocket, 1933) as well as to the health measures instituted. At the same time it must be remembered that ignorance and prejudice make certain measures impracticable in a community, especially one that is backward. Material for the survey When collecting the material for this paper, I went through all the parish registers in the Colony from 1857 to 1956, extracting data about the death of every person registered as having died from tuberculosis in any form. Details about whites and other races are not included. In the early part of the century surveyed a number of vague terms were used, which I have had to exclude, so that my statistics about the death rate are likely to err in being lower than the correct figure, but they are as reliable as I have been able to make them. In going through the registers it was noticeable after the turn of the century, i.e. after the significance of the discovery of Koch's bacillus and its relation to tuberculosis was appreciated, that the use of many vague terms diminished. Influence of treatment on the mortality This paper deals with the epidemiology and mortality of tuberculosis, but when considering the details of the survey it is necessary to bear in mind that the influence of chemotherapy does not enter until well after the last war, when the drugs were first used in Antigua. BCG has not yet been applied in Antigua other than to the nursing staff of the local hospital. Other methods of treatment, such as pneumothorax, have only exceptionally been used, and will not have had any noticeable effect on my figures. There has been a hospital for the poor in Antigua since the 1830's, to which many chronic patients have been admitted over the years. The ratio of general hospital and infirmary beds per 1,000 of the population has never been more than the present figure of 3·5, and before the war it was less. Social services did not exist until after the war, and any voluntary philanthropic organisations were too impecunious to be able to attack the problems raised by this disease. It is a reasonable inference that very little change occurred either in the treatment or care of tuberculosis patients over the century until the last war.
447
TUBERCULOSIS IN ANTIGUA TABLE I.-TUBERCULOSIS IN ANTIGUA, CRUDE DEATH RATE, BY DECADES, 1857 - 1956
Crude death ratefrom tuberculosis, per 100,000
Decade
Number of deaths by sex
Males
Females
Persons
Males
Females
Persons
1857 - 1866 1867 -1876
4390 3910
4799 4059
4609 3991
748 611
925 754
1673 1365
1877 - 1886 1887 - 1896
2607 2947
2565 3059
2584 3007
414 498
473 588
887 1086
1897 -1906 1907 - 1916
2408 1854
2826 2031
2637 1954
362 244
515 350
877 594
1917 - 1926 1927 - 1936
1443 901
1884 968
1698 939
176 130
314 185
490 315
1937 - 1946 1947 - 1956
793 493
828 427
813 458
132 109
171 106
303 215
3424
4381
7805
i
The survey
During the hundred years under survey there were 3,424 deaths in males and 4,381 in females from the disease in all its forms. The crude death rate in decades for each sex and for persons is shown in Table I. A breakdown to an annual death rate is not justified for such a small population as that of Antigua; the secular changes as shown decade by decade give a reasonably clear representation of what has been happening over the century. The most striking feature is the steady and very considerable fall in mortality that has taken place over the century. In the decade 1947-1956 this was 11 % of what it was a century ago in males and 9 %in females. The fall has been equal in the two sexes and indeed the difference in the crude rate between them has usually been very slight TABLE Il.-STANDARDISED DEATH RATES FROM TUBERCULOSIS (ALL FORMS), ANTIGUA, 1857 - 1956
Standardised death rate per 1,000 living
--
England and Wales
Antigua Decade
Males Females
Persons
Decade
Males Females
Persons
1857 - 1866 1867 -1876
4-48 4'01
4-91 4·06
4'66 4'02
1851 - 1860 1861 -1870
3·48 3·36
3-48 3·18
3-48 3'26
1877 - 1886 1887 - 1896
2·66 2·97
2'59 3·00
2·63 2-98
1871-1880 1881 -1890
3·08 2-66
2·70 2·25
2-88 2·44
1897 -1906 1907 - 1916
2·53 2-05
2-85 2·05
2'71 2'05
1891 -1900 1901 - 1910
2·29 1·89
1·78 1-42
2·02 1·65
1917 -1926 1927 - 1936
1·69 0'99
1'97 1·01
1'85 1·00
1911 -1920 1921-1930
1·55 I'll
1·22 0·89
"38 0·99
1937 - 1946 1947 - 1956
0'86 0·56
0'86 0·44
0·86 0·48
1931 - 1940 1941 -1950
0·78 0·65
0·61 0-45
0'70 0·55
NOTE: Data for England and Wales for 1851 - 1930 from Jameson and Parkinson (1952), p. 89 and for 1931 -1950 from Ministry of Health (1958), p. 268. Standardisation is against the England and Wales population in 190 I.
448
TUBERCLE
over the century. A rise took place in the decade 1887-1896. This occurred during a period of severe droughts and economic depression, which resulted in near starvation of numbers of people, who in any case were near the borderline of malnutrition even in years when there was comparative prosperity. The droughts, leading to failure of the sugar crops, meant considerable unemployment among the poorer classes. The associated rise in the tuberculosis death rate would therefore be expected. The rise is more marked in females than in males and took longer to subside. This too would be expected, because the adult female usually works harder than does the male in the West Indies, so that if infected, her exhausted and under-nourished condition, especially when pregnant or nursing, would create a favourable situation for the spread of the disease. The standardised death rate for tuberculosis has been worked out for each decade. using the England and Wales population of 1901 as the basis. The results are shown in Table Il, with the corresponding figures for England and Wales for comparison: On the whole, the values for the standardized death rate for each sex and for persons follow very closely those for the crude rate, much more so than might have been expected. For the last thirty years the death rate has been much the same for Antigua as for England and Wales. Before that date the former was higher than the latter, but only moderately so. One would have expected a much greater disparity in a backwai d tropical community. As Yerushalmy (1946) stated, 'before we can be confident that satisfactory 01 consistent progress is being made in the control of a preventable disease, (the fall in its death rate) must be faster than the rate of decline of the total death rate.' Progress in control can therefore be measured by the improvement in the proportionate mortality ratios, which express the number of deaths from a given cause as a percentage of the total number of deaths. Table III shows that there has been a steady improvement in the proportionate mortality ratio in Antigua. Table IV shows that there has been a continuous fall, except for the decade 1887 - 1896, until 1947-1956, when the mortality was only 10 %of that of a century ago. This improvement appears to have been part of the general improvement that has occurred throughout the world wherever statistics are dependable enough to show secular changes. I t can be argued that a part of this fall is due to a developing racial immunity. The course of the disease in Antigua, as Cochrane (I938) has argued for British Guiana, suggests that tuberculosis TABLE IlL-THE TUBERCULOSIS RATE AS A PERCENTAGE OF THE DEATH RATE, IN DECADES
DEATH CRUDE
Tuberculosis death rate x 100 Decade Crude death rate 1857- 1866 J867 -1876
12'5 10'8
1877- 1886 1887 - 1896
7'3 9'4
1897 - 1906 1907-1916
8·5 7·Q
1917- 1926 1927- 1936
6·3 4'9
1937-1946 1947 -1956
4'5 4·Q
The corresponding value for England and Wales in 1951 was 0·3 (Ministry of Health, 1952).
NOTE:
449
TUBERCULOSIS IN ANTIGUA TABLE IV.-THE CRUDE DEATH RATE FROM TUBERCULOSIS AS A PERCENTAGE OF THAT FOR 1857 - 1866, IN DECADES
-
Decade
Males
Females
Persons
1857 - 1866 1867 - 1876
100 89
100 85
100 87
1877 - 1886 1887 - 1896
59 67
53 64
56 65
1897 - 1906 1907 - 1916
55 42
59 42
57 42
1917 - 1926 1927 - 1936
33 21
39 20
37 20
1937-1946 1947-1956
18 11
17 9
18 10
was a new disease to the slaves arriving in the early nineteenth century; so long as they were isolated on estates the disease did not become a national problem, but the liberation of 1834, with its associated greater mixing of populations in newly established villages led to a rapid spread of tuberculosis. The matter will be referred to again when discussing cohort analysis. The slow but steady improvement in the statistics is, on this basis, a result of the gradual weeding out of the more susceptible, and the building up of a slight but definite racial immunity. TABLE V.-TUBERCULOSIS DEATHS FOR THE CENTURY 1857 -1956 BY AGE AND SEX, WITH THE PERCENTAGE OF THE TOTAL OCCURRING AT EACH AGE
Deaths from tuberculosis, all forms Females
Males Age group
Number
Percentage
Number
Percentage
05 -
342 65
9·99 1·90
344 97
7·85 2·21
1015-
108 232
3·15 6·78
133 357
3·04 8·15
2025-
501 437
14·63 12·76
684 579
15·61 13·22
3035-
391 304
11·42 8·88
542 377
12·37 8·61
4045-
286 242
8·35 7·07
402 241
9·18 5·50
5055-
206 99
6·02 2-89
249 118
5·68 2·69
6065-
118 45
3045 1·31
125 43
0'98
7075 and over
24
0·70
50
1·14
24
0·70
40
0·91
Total
3424
4381
2-85
450
TUBERCLE AGE AND SEX DISTRIBUTION OF TUBERCULOSIS MORTALITY
Table V shows the deaths from this disease over the century, divided as to sex and age. There are slight differences between the percentages for the sexes, but these are not statistically significant. The peak for each sex is 20-24 years of age, preceded by a somewhat rapid rise with a slower fall in later years. The closeness of the curves for the two sexes is indeed remarkable, and is quite different from experience in England and Wales. In the West Indies young women expect to become pregnant in their early teens, and one would have thought that the strain of adolescence combined with that of early and many pregnancies would have raised the curve for females considerably higher than that for males. The closeness of the two curves to each other may be related to the open air life led by both sexes of all ages. The rates for each sex, arranged in decades, are shown in Table VI and Figs. 1 and 2. AVERAGE OF:
_._.-
1857-1876 1877-1926 1927-1956
AVERAGE OF: t/)
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AGE GROUPS (YEARS)
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Fig. 1 Tuberculosis death rates by age groups (males) between 1857 and 1956.
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AGE GROUPS (YEARS) Fig. 2
Tuberculosis death rates by age groups (females) between 1857 and 1956.
Males There is the usual high mortality in the very early years met with all over the world. The age group 5-9 years has always been one with a minimal mortality, but thereafter, with the onset of the strain of adolescence, the rate rises rapidly. At ages 25-54 the figures show a curve of the adult plateau type with high rates up to 8 per 1,000 in some age groups for the first two decades of the century under review, twice the England and Wales maximum for 1851-60 at age 25-34 years; this fell to a moderately steady 3-4 per 1,000 throughout the next five decades. From 1927 onwards the most characteristic feature of the curves is the great fall for each decade, though the peak remains at 25-34 years of age. During the last three decades, along with the fall in the rate at ages in early and middle adult life, the plateau type of curve has changed to one with two peaks, a main one still at 25-34 years of age, and a lesser one at 45-54 or later. In the age group 55-64 years the male mortality is higher than that for fenales. The numbers of the population aged 65 and over are small and it would be unjustified to draw any conclusion other than to state that the disease is present into extreme old age.
451
TUBERCULOSIS IN ANTIGUA TABLE VI.-TUBERCULOSIS IN ANTIGUA
Mean annual mortality per ],000 living at various ages, in quinquennia up to age [4 years, in decennial periods thereafter MALES Age
0-4 5 - 9 10-14
1857 1862 1867 1872 18771882188718921897190219071191211917 192219271932193719421947 1952 -61 -66 -71 -76 -81 -86 -91 -96 -01 -06 -11 -16 -21 -26 -31 -36 1--41 --46 -51 -56
- - -- - - - - - - - - - - - - - - 1-6 [,4 2-6 0'8 2'8 6·1 4·2 2-9 1-6 2·4 1'7 [,0 N 0'6 10:31-0.5 0·3 0·06 - - - ------ -- - - - -- j - - 0'8 0·2 0·8 0'2 0·7 0·5 0'7 0·4 0'3 0'2 0'2 0·2 0·3 0'3 0·2 l().l 0,[ D,] --- - ---- - ],0 I
0·7 0·2
H
0'8 0·8 H
['4 0·7
- -- -- -
0'3
o:s
I
--I- I
0-3 0'3 0·2 0'5
0,]
-,----:-
[5-24
4·3
3·7
3'2
2·9
2·5
J ·9
J ·9
J ,2
25-34
6·9
6·5
4'5
4-0
3·7
3'3
2-9
2'2
0'[ 0'5 0'3
! 0'9
0·4
1-6
],0
--35-44
6·5
6·4
3·7
~'7
3-9
2'8
45-54
8·0
6·4
4·2
3·7
3·2
2·7
55-64
8·2
5-8
3·0
H
2-3
65-74
5·6
4'5
2·2
J ·3
1'8
3·J
0·8
J·2
0·7
2·0
0·6
1-3
1-3
],7
1'1
J·5
rr
r-o
0·6
0·6
r-s
0·8
0·2
I
1862 Cohort FEMALES Age
185718621186711872187718821887 1892118971190211907 19121917 192211927 1932193719421947 1952 -61 -66. -71 -76 -81 -86 -91 -96 -01 -06 -11 -16 -21 -26 -31 -36 --41 --46 -51 -56
i J·O
i
0-4
2·J
5 - 9
0'9 0·2 0·8 0'31 0'7 0·5
10-14
3·3 0·9
['8
5·J
3'714'2 1-6 1-8 ]'5 J'2
l-81~'7
0·2 0'[
0'[
~
0·4 1·3 0'61 0'6 0'4 0-7 0'8 0·2 0-2 0'3 0·2 0'3
-
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-------------,-----------------
15-24
6,'
25-34
8·1
35-44
7 '1
I
s-s
Jo2
,.,
3"
6·5
4·9
4-4
4·0
7-l
3'7
4·2
2·4
I
2'4
a-s
1'6
'4
0,'
3'2
3·9
2·2
1'5
0'5
3-4
3,]
2'6
0·8
H
0'7
3']
3-8
2-6
1·5
0·9
0'8
0·9
2-3
2'0
],6
0·7
0·7
0·5
2'5
0·5
0·7
0'8
0,3
I
I 45-54
6-J
6·3
55-64
6·8
4'5
65-74
3·7
2·6
I
I I
I I 1
]'8
j'7
I I ,
I
J '8
,
I
I
0·6
0·5
I
•
1862 Cohort
452
TUBERCLE
Females The minimum mortality is at ages 5-9 years, though this is usually higher than that for males of the same age and decade. Then follows the group aged 9-14 years, again somewhat higher than its fellow in the male series. The age group 15-24 shows the rapid rise characteristic of the mortality of the disease at this age throughout the world; the value for each decade is either the same as or higher than its fellow in the male series. As in the case of the males, the curves for females in the first two decades of the hundred years are very high, though they fall more rapidly with age. During the decades 1877 to 1926 the curves for females resemble closely those for males in the same years, likewise being at a much lower level than in the period 1857-1876, the curve for each decade being lower than its predecessor. The curves for the last three decades form a unit, as with the corresponding ones for males, being the lowest for the century, with each decade being an improvement on its predecessor. The peak mortality at 25-34 years of age tends to be higher than the corresponding one for males. In extreme old age the tendency is for the female mortality to fall more consistently than in the case of males. There has been no shift in the peak of maximum mortality to older age groups in either sex in Antigua, such as has occurred in England and Wales and elsewhere in Europe. In Table VII the crude death rate from tuberculosis at ages for the first three decades is followed by similar information about the last three decades under review, in order to bring out clearly the the change that has taken place. During the first three decades there was a slight preponderance of mortality among females up to the age group 35-44, since when there has been a definite male preponderance. This male preponderance may be due to the large number of older men living by themselves under unsatisfactory conditions, a manner of living common in the West Indies. The lower ratio in the earlier decades in women of child-bearing age is almost certainly due to the stresses of pregnancy, more especially as pregnancy does not involve any cessation of manual work for more than a very few weeks. Why the ratio in the whole population has changed in recent decades is not so easily explained, but a possible reason is that men's living and working conditions may have improved faster than have those of women. COHORT ANALYSIS
By the term cohort is meant the survivors at any age of all persons born in a given year or group of years. The material for such an analysis can be obtained from tables such as Table Vl, which gives the mean annual mortality per 1,000 living at ages, but the grid must be traversed diagonally TABLE VII.-RATIO OF MALE TO FEMALE MORTALITY FROM TUBERCULOSIS AT AGES PER 1,000 LIVING
Age group (years)
Ratio of male to female mortality
1857-1886
1927 -1956
05 -
0·98 0'89
1'57 0·60
15-
10-
0'83 0'82
1·75 0'71
2535-
0·92 0·92
1'14 1·04
4555-
1'26 ',30
1·23 1·89
6575-
1-54 '-94
J ·61 0·24
453
TUBERCULOSIS IN ANTIGUA
(not verticall y) so as to ensure that each successive square shows a mortality rate derived fr om the survivors of those in the previous age group. In the table referred to, the identifying birth date of each cohort will be that of the central year which will provide five years of life experience to the quinquennium block, (or ten years to the decennium , as the case may be,) and will not appear in any contiguous cohort. The cohorts for Antigua show that the age of maximum mortality is always 25-34 years of age in males, and usually so in the case of females , with a steady fall in each sex to old age. This corresponds with experience in England and Wales. (Springett 1950). The tendency for the peak of the adult female mortality curve to mo ve back in recent years from the age group 25-34 years to that of 15-24 years, (as is the case also in England and Wale s.) indicat es some fundamental change in the age distribution of mortality, to the disadvantage of the female . Such a change has not taken place in the male. Apart from this, the general uniformity of the falls of the cohort mortality values is an indication that violent changes have not occurred in the mortality from tuberculosis of the negro in Antigua since the time that records have been kept. The main change is essentially one of a steady reduction in the mortality at all ages, - probably due to a slow elimination of the ope n type of pulmonary tuberculosis, such as is also occurring in Europe and North America. This more constant dist ributio n over the age of fifteen years in the cohort, as opposed to a tendency for a rise to occur in the decennial values, i.e. when the table is read from above downwards, implies that the mortality of a group in later life is to a cons iderable degree determined by conditions in infancy and childhood. The absence of a shift in the peak of the cohort mortali ty in either sex from 25-34 years of age to older age groups confirms experience in England and Wales and the more populous areas of Europe. The changes taking place over the years in the cohorts in Antigua can be seen in Ta ble VIII, where the mortalities at various ages have been expressed as a percentage of that at age 25-34 years in the same co hort. The infancy and early childhood rate was low until the decade of severe d ro ughts and economic depression, 1887-1896, since when the rate, as in England and Wales, has been much higher than that for the age group 25-34 years. I am unable to offer any explanation for the low figures before 1887. Apart from the rate in infancy, the table also shows a very constant type of mortality curve for each decade. In this respect it resembles similar cohort tables for England and Wales, with the maximum almost always in the 25-34 year age group . TABLE VIII.-MoRTALlTY AT VARIOUS AGES, AS A PERCENTAGE OF THAT AT AGE 25 - 34 YEARS IN THE SAME COHORT. COMBIN ED SEXES
Cohort
Age group
0-
5-
1827 - 36 1837 - 46
15-
25-
35-
45-
55-
65-
75-
81
100 100
90 57
42 51
38 33
30 8
11 4
II
1847 - 56 1857 - 66
39
18
80 71
100 100
84 85
75 63
35 19
26
16 19
1867 -76 1877 - 86
53 47
18 21
83 99
100 100
78 89
44
24
26 26
21
23
1887 - 96 1897 - 06
124 118
24
68 103
100 100
22
28 47
19
24
1907 -16 191 7 - 26
121 196
31 31
94 157
100 100
43
I7
57
8
454
TUBERCLE
Figs. 3 and 4 show that cohort values for succeeding decades have fallen considerably and very consistently. In my opinion it is reasonable to infer from the early ones that not only adult mortality rates were very high in the second quarter of the nineteenth century, but that in all probability so were those for infants and children. The early curves have the characteristics associated with a severe epidemic, with the serious phase of the epidemic ending soon after the turn of the century. I suggest that the cause of the epidemic was the liberation of the slaves in 1834. While the slaves lived and worked on thinly populated estates in considerable isolation from their fellows elsewhere,
7
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there could be but few chances of becoming infected with tubercle bacilli, and those infected would therefore in the main be the 'non-immune'. As soon as the slaves were liberated they went to live in newly created, large congested villages, where the spread of the disease, once introduced by an open case, would be rapid among a susceptible community. The high death rates at ages 15-34 years in the two decades immediately following 1857 were in those who as infants were taken by their parents at the liberation of the slaves from the estates to live in the villages. Young nonimmune mothers in the 1830's and 1840's contracting tuberculosis for the first time under these conditions would quickly become infectious themselves, resulting in a major epidemic that spread rapidly through all ages, not only in infants and children, and was only slowly followed by a decline in severity. On comparing the cohort tables for England and Wales, and those for Antigua one is struck by
455
TUBERCULOSIS IN ANTIGUA
the similarities rather than the differences, and with the inevitable conclusion that similar factors must have been playing their part in influencing the mortality from tuberculosis in the two localities. In other words, the congestion caused by the industrial revolution in England and Wales led to an epidemic of tuberculosis in the mid nineteenth century; similarly, the liberation of the slaves in Antigua produced a severe outbreak of the disease about the same time for similar reasons. It makes one wonder whether too much emphasis may have been placed on race in the past as being an important factor influencing mortality.
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Discussion It is evident that in Antigua, as elsewhere in the world, many factors are involved in preventing a more rapid fall in the mortality from the disease - poverty, bad housing, an unbalanced diet with its resulting poor health, night time overcrowding, and the presence of slums, But I have been impressed with the views of older experienced physicians, e.g. Cory (personal communication), who were certain that in Jamaica thirty years ago the disease as met by them was a much more rapidly advancing and fatal condition than it is today, quite apart from the more favourable prognosis now possible by the use of modern drugs. Living conditions in Jamaica have not improved F
456
TUBERCLE
sufficiently for them to be an important factor in this improvement. The same remarks apply to Antigua. Nevertheless, the mortality in Antigua has improved very much during the last half century and is now comparable with that of England and Wales a decade or two ago. This improvement is due to a slow but steady change in social and economic conditions, and the development of a relative immunity in the population following the high prevalence of the disease over the last 150 years, with the gradual elimination of the more susceptible. Certain causes that are often advanced as reasons for a fall in the rate do not apply to any great extent, such as a reduction in the size of the family, which is as large in Antigua as it ever was, nor to education, since any improvement in this field was of litt1e note until after the last war. A school health service is still practically non-existent, and infant welfare work began only ten years ago. The conditions of work have changed very little over the century, the peasant workers farm in the main in the same way as did their grandparents, even when a tractor does the rough ploughing or hauling for them. As regards the therapeutic factor of new drugs, this was of no significance until ten years ago. This paper is one of a series by the author dealing with the epidemiology of disease in the negro in Antigua, assisted by a grant from the Standing Advisory Committee for Medical Research in the British Caribbean, for which the author wishes to express his grateful thanks. REFERENCES COCHRANE, E. (1938). Tubercle, Lond., 19, 403. CROCKET, J. (1933). J. State, Med., 41, 164. GILMOUR, W. S. (1944). Caribbean med. J., 6, 171. JAMESON, W. W., & PARKINSON, G. S. (1952). A Synopsis of Hygiene, 10th edition, edited by L. Roberts and K. M. Shaw, p. 89, J. & A. Churchill, London. MINISTRY OF HEALTH (1952). Report of the Ministry of Health for the Year 1951. Part 2. On the State of the Public Health, p. 202, H.M.S.a., London. MINISTRY OF HEALTH (1958). Report of the Ministry of Health for the Year 1957. Part 2. On the State of the Public Health, p. 268, H.M.S.a., London. Sl'RINGETT, V. H. (1950). J. Hyg., Camb., 48, 361. WILCOCKS, C. (1932). E. Afr. med. J., 9, 88. YERUSHALMY, J. (l946). Publ. Repts, Wash., 61, 251.
nu».
Tubercle, Lond., (1961), 42, 444
TUBERCULOSIS MORTALITY IN THE NEGRO POPULATION OF ANTIGUA, BRITISH WEST INDIES, OVER THE LAST HUNDRED YEARS by K. H.
UTTLEY
Medical Department, St. John's, Antigua, West Indies SUMMARY
An investigation of death records since 1857 has been carried out in Antigua, West Indies, to find out the mortality from tuberculosis over the century in the negro inhabitants. The island is favourably placed for such a survey, because censuses have been taken at frequent intervals, births and deaths registration and the recording of the cause of death have been good over the period in question, and it has been possible to separate the records of those of African descent from those of other races. The population is an agricultural one, self-contained, whose numbers fluctuated between 29,000 and 54,000. The crude death rate from the disease at the beginning of the hundred years was 4·6 per 1,000; it fell to 0·46 in 1947-56. Standardised against the England and Wales population of 1901 the corresponding figures were 4·66 and 0·48. The fall in mortality was uniform except for one decade of severe droughts and economic depression. For the last thirty years the mortality has been roughly the same as that of the United Kingdom. In the mid-nineteenth century tuberculosis accounted for 11 % of all deaths; a century later the percentage was 4. Over the whole century the variations in the sex ratio of all tuberculosis deaths were not statistically significant, but at times there have been considerable differences between the sex ratio of the disease at different ages. The mortality curves at ages for each sex show a material fall with each succeeding decade of the century. A study of cohort mortality curves in Antigua shows more similarities with corresponding curves in England and Wales than might have been expected in a tropical locality. It is also possible to infer from these curves that a likely cause of the mid-nineteenth century epidemic of tuberculosis in the island was the freeing of the slaves in 1834, who went straight from the isolation of relatively healthy estate life to the congestion of crowded and unhygienic villages. The evidence of the negro tuberculosis mortality in Antigua suggests that perhaps too much emphasis may have been placed in the past on race as being a major factor in influencing mortality rather than on elements in the environment.
Antigua is a small island of 108 square miles in area. It is one of the Leeward Islands, which lie between Puerto Rico on the west, and the Windward Islands, Martinique and Barbados to the south-east. Except for the southwestern third of the island, with hills rising to 1,330 feet, it consists of undulating plains and low hills. The trade winds can blow freely over its whole extent and there is not the hot muggy weather so frequently met with in the neighbouring mountainous islands. This has a corresponding disadvantage in that the lack of high hills and their cloud cap result
TUBERCULOSIS IN ANTIGUA
445
in a low rainfall of 45 to 50 inches a year, half of which occurs between August and December. Variations in the amount of annual rainfall are considerable and the island is subject to long periods of severe drought every few years. Temperatures are equable and it is unusual to have a variation of more than ten degrees from the annual mean of 79° F. The people are mostly of African descent, with perhaps 10% of mixed blood; during the period under review the white population was never more than 5 % of the total and was usually much less. There has never been any East Indian population. The Antiguans are engaged in agriculture. About 22 % live in the only town; the remainder live in forty small compact villages of 200 to 1,500 inhabitants, grouped evenly over the island. The town, with 12,000 residents, has wide streets, with few narrow alleyways; most buildings have only one floor, the houses and huts are spaced away from each other; the town extends along a harbour, and although there is a small area of slum no point in the town is more than 600 yards from open country. Most of the houses of the island, whether in town or country, consist of small huts of under 200 square feet in area. They stand in their own little yards, surrounded by collections of rubbish, old cans, bottles, boxes and household refuse. At nights the windows and doors are kept tightly shut to exclude the 'spirits'. Such an arrangement is an excellent one for the familial spread of tuberculosis, which is the main manner of spread of that disease in Antigua, but apart from this, the isolation of the house reduces the risk for outsiders (Gilmour, 1944). The family lives out of doors for sixteen hours out of the twenty four, and the sunshine and space make contact at that time much less than it would be in colder climates. Although village houses are dirty and surrounded by refuse, there has not been the squalor and congestion that have prevailed in the cities and towns of Europe and North America. A large proportion of the women work in the fields for much of the year, whether or not they are pregnant ornursing, There is a season of the year after the sugar cane has been cut, from August to December, when there is unemployment among the men. No records of unemployment are kept, but in years of drought it must be extensive. The diet has always been an unbalanced one, with an undue predominance of carbohydrates. A porridge of powdered Indian corn, (maize.) is the staple source of energy; in the cane-cutting season from January to July, this is supplemented by chewing considerable amounts of sugar cane stems. Meat and milk products have always been very deficient in the diet, and it is only in the last decade that attention has been given to any great extent to the catching of fish. For months at a time vegetables are not available or are beyond the reach of the poor, but as regards fruit, mangoes are an important article for two months of the year. The little milk that is drunk is always consumed boiled, for climatic reasons. A hundred years ago the population was 36,000; it fell slowly to 28,800 in 1921, but has risen rapidly since the early thirties owing to the great fall in the infant death rate, and in 1956 it was 54,200. There has been a certain amount of emigration at times of unemployment, mostly of young men; at the beginning of the century many went to the Panama Canal Zone to work on the construction of the Canal; on other occasions they have emigrated to the United States, and at present they are going to the United Kingdom. All the same, the population is a self-contained one and had little contact with the outside world in the earlier part of the period under review. At censuses 5 % to 10% of the population claimed to have been born outside the Colony. Since 1856 there have been eight censuses: in 1861, 1871, 1881, 1891 1901 (total for the sexes only), 1911, 1921 and 1946. Probably a certain proportion of the very young escaped enumeration at the earlier censuses; apart from this it is likely that the totals for each sex were fairly accurate, but there are bound to be many errors as regards stated age when one is dealing with uneducated, rural tropical communities, where people frequently have little idea of their correct ages. There has been a considerable preponderance of females over males in all the age groups beyond early childhood. Associated with a male/female live birth ratio of 1030, which is much lower than that
446
TUBERCLE
for England and Wales, is the fact that the ratio ofthe sexes at ages of 15 years and over is 754 males to 1,000 females, a ratio that has not varied much from one decade to another. Births and deaths registration, introduced and made compulsory in 1856, became reasonably accurate in the course of a decade. Factors influencing this accuracy were: 1. There were sufficient physicians throughout the period who had been trained in the British Isles or in Canada; 2. The island is a small one and has good communications; 3. A series of ordinances culminated in that of 1880 by which a midwifery service was established; insofar as numbers of midwives are concerned, this was in my opinion more than enough to handle all births - there was one midwife to 1,200 inhabitants; 4. As regards the burial of the dead, no dead body could be buried without a burial order, which in turn could not be supplied without the production of a physician's or coroner's certificate of the cause of death. The accuracy of death returns, vary from country to country, so that it is likely that among the international comparisons which I have made there may be some that are invalid; but in this matter I would like to quote Wilcocks (1932) who wrote: 'It should not be overlooked that observers of long ago were no more lacking in clinical acumen than (present day) men who have so many more advantages'. In Antigua, as in the tropics generally, the mortality from tuberculosis may be considered an 'index pointing to the conditions of life and work prevailing in the region' (Crocket, 1933) as well as to the health measures instituted. At the same time it must be remembered that ignorance and prejudice make certain measures impracticable in a community, especially one that is backward. Material for the survey When collecting the material for this paper, I went through all the parish registers in the Colony from 1857 to 1956, extracting data about the death of every person registered as having died from tuberculosis in any form. Details about whites and other races are not included. In the early part of the century surveyed a number of vague terms were used, which I have had to exclude, so that my statistics about the death rate are likely to err in being lower than the correct figure, but they are as reliable as I have been able to make them. In going through the registers it was noticeable after the turn of the century, i.e. after the significance of the discovery of Koch's bacillus and its relation to tuberculosis was appreciated, that the use of many vague terms diminished. Influence of treatment on the mortality This paper deals with the epidemiology and mortality of tuberculosis, but when considering the details of the survey it is necessary to bear in mind that the influence of chemotherapy does not enter until well after the last war, when the drugs were first used in Antigua. BCG has not yet been applied in Antigua other than to the nursing staff of the local hospital. Other methods of treatment, such as pneumothorax, have only exceptionally been used, and will not have had any noticeable effect on my figures. There has been a hospital for the poor in Antigua since the 1830's, to which many chronic patients have been admitted over the years. The ratio of general hospital and infirmary beds per 1,000 of the population has never been more than the present figure of 3·5, and before the war it was less. Social services did not exist until after the war, and any voluntary philanthropic organisations were too impecunious to be able to attack the problems raised by this disease. It is a reasonable inference that very little change occurred either in the treatment or care of tuberculosis patients over the century until the last war.
447
TUBERCULOSIS IN ANTIGUA TABLE I.-TUBERCULOSIS IN ANTIGUA, CRUDE DEATH RATE, BY DECADES, 1857 - 1956
Crude death ratefrom tuberculosis, per 100,000
Decade
Number of deaths by sex
Males
Females
Persons
Males
Females
Persons
1857 - 1866 1867 -1876
4390 3910
4799 4059
4609 3991
748 611
925 754
1673 1365
1877 - 1886 1887 - 1896
2607 2947
2565 3059
2584 3007
414 498
473 588
887 1086
1897 -1906 1907 - 1916
2408 1854
2826 2031
2637 1954
362 244
515 350
877 594
1917 - 1926 1927 - 1936
1443 901
1884 968
1698 939
176 130
314 185
490 315
1937 - 1946 1947 - 1956
793 493
828 427
813 458
132 109
171 106
303 215
3424
4381
7805
i
The survey
During the hundred years under survey there were 3,424 deaths in males and 4,381 in females from the disease in all its forms. The crude death rate in decades for each sex and for persons is shown in Table I. A breakdown to an annual death rate is not justified for such a small population as that of Antigua; the secular changes as shown decade by decade give a reasonably clear representation of what has been happening over the century. The most striking feature is the steady and very considerable fall in mortality that has taken place over the century. In the decade 1947-1956 this was 11 % of what it was a century ago in males and 9 %in females. The fall has been equal in the two sexes and indeed the difference in the crude rate between them has usually been very slight TABLE Il.-STANDARDISED DEATH RATES FROM TUBERCULOSIS (ALL FORMS), ANTIGUA, 1857 - 1956
Standardised death rate per 1,000 living
--
England and Wales
Antigua Decade
Males Females
Persons
Decade
Males Females
Persons
1857 - 1866 1867 -1876
4-48 4'01
4-91 4·06
4'66 4'02
1851 - 1860 1861 -1870
3·48 3·36
3-48 3·18
3-48 3'26
1877 - 1886 1887 - 1896
2·66 2·97
2'59 3·00
2·63 2-98
1871-1880 1881 -1890
3·08 2-66
2·70 2·25
2-88 2·44
1897 -1906 1907 - 1916
2·53 2-05
2-85 2·05
2'71 2'05
1891 -1900 1901 - 1910
2·29 1·89
1·78 1-42
2·02 1·65
1917 -1926 1927 - 1936
1·69 0'99
1'97 1·01
1'85 1·00
1911 -1920 1921-1930
1·55 I'll
1·22 0·89
"38 0·99
1937 - 1946 1947 - 1956
0'86 0·56
0'86 0·44
0·86 0·48
1931 - 1940 1941 -1950
0·78 0·65
0·61 0-45
0'70 0·55
NOTE: Data for England and Wales for 1851 - 1930 from Jameson and Parkinson (1952), p. 89 and for 1931 -1950 from Ministry of Health (1958), p. 268. Standardisation is against the England and Wales population in 190 I.
448
TUBERCLE
over the century. A rise took place in the decade 1887-1896. This occurred during a period of severe droughts and economic depression, which resulted in near starvation of numbers of people, who in any case were near the borderline of malnutrition even in years when there was comparative prosperity. The droughts, leading to failure of the sugar crops, meant considerable unemployment among the poorer classes. The associated rise in the tuberculosis death rate would therefore be expected. The rise is more marked in females than in males and took longer to subside. This too would be expected, because the adult female usually works harder than does the male in the West Indies, so that if infected, her exhausted and under-nourished condition, especially when pregnant or nursing, would create a favourable situation for the spread of the disease. The standardised death rate for tuberculosis has been worked out for each decade. using the England and Wales population of 1901 as the basis. The results are shown in Table Il, with the corresponding figures for England and Wales for comparison: On the whole, the values for the standardized death rate for each sex and for persons follow very closely those for the crude rate, much more so than might have been expected. For the last thirty years the death rate has been much the same for Antigua as for England and Wales. Before that date the former was higher than the latter, but only moderately so. One would have expected a much greater disparity in a backwai d tropical community. As Yerushalmy (1946) stated, 'before we can be confident that satisfactory 01 consistent progress is being made in the control of a preventable disease, (the fall in its death rate) must be faster than the rate of decline of the total death rate.' Progress in control can therefore be measured by the improvement in the proportionate mortality ratios, which express the number of deaths from a given cause as a percentage of the total number of deaths. Table III shows that there has been a steady improvement in the proportionate mortality ratio in Antigua. Table IV shows that there has been a continuous fall, except for the decade 1887 - 1896, until 1947-1956, when the mortality was only 10 %of that of a century ago. This improvement appears to have been part of the general improvement that has occurred throughout the world wherever statistics are dependable enough to show secular changes. I t can be argued that a part of this fall is due to a developing racial immunity. The course of the disease in Antigua, as Cochrane (I938) has argued for British Guiana, suggests that tuberculosis TABLE IlL-THE TUBERCULOSIS RATE AS A PERCENTAGE OF THE DEATH RATE, IN DECADES
DEATH CRUDE
Tuberculosis death rate x 100 Decade Crude death rate 1857- 1866 J867 -1876
12'5 10'8
1877- 1886 1887 - 1896
7'3 9'4
1897 - 1906 1907-1916
8·5 7·Q
1917- 1926 1927- 1936
6·3 4'9
1937-1946 1947 -1956
4'5 4·Q
The corresponding value for England and Wales in 1951 was 0·3 (Ministry of Health, 1952).
NOTE:
449
TUBERCULOSIS IN ANTIGUA TABLE IV.-THE CRUDE DEATH RATE FROM TUBERCULOSIS AS A PERCENTAGE OF THAT FOR 1857 - 1866, IN DECADES
-
Decade
Males
Females
Persons
1857 - 1866 1867 - 1876
100 89
100 85
100 87
1877 - 1886 1887 - 1896
59 67
53 64
56 65
1897 - 1906 1907 - 1916
55 42
59 42
57 42
1917 - 1926 1927 - 1936
33 21
39 20
37 20
1937-1946 1947-1956
18 11
17 9
18 10
was a new disease to the slaves arriving in the early nineteenth century; so long as they were isolated on estates the disease did not become a national problem, but the liberation of 1834, with its associated greater mixing of populations in newly established villages led to a rapid spread of tuberculosis. The matter will be referred to again when discussing cohort analysis. The slow but steady improvement in the statistics is, on this basis, a result of the gradual weeding out of the more susceptible, and the building up of a slight but definite racial immunity. TABLE V.-TUBERCULOSIS DEATHS FOR THE CENTURY 1857 -1956 BY AGE AND SEX, WITH THE PERCENTAGE OF THE TOTAL OCCURRING AT EACH AGE
Deaths from tuberculosis, all forms Females
Males Age group
Number
Percentage
Number
Percentage
05 -
342 65
9·99 1·90
344 97
7·85 2·21
1015-
108 232
3·15 6·78
133 357
3·04 8·15
2025-
501 437
14·63 12·76
684 579
15·61 13·22
3035-
391 304
11·42 8·88
542 377
12·37 8·61
4045-
286 242
8·35 7·07
402 241
9·18 5·50
5055-
206 99
6·02 2-89
249 118
5·68 2·69
6065-
118 45
3045 1·31
125 43
0'98
7075 and over
24
0·70
50
1·14
24
0·70
40
0·91
Total
3424
4381
2-85
450
TUBERCLE AGE AND SEX DISTRIBUTION OF TUBERCULOSIS MORTALITY
Table V shows the deaths from this disease over the century, divided as to sex and age. There are slight differences between the percentages for the sexes, but these are not statistically significant. The peak for each sex is 20-24 years of age, preceded by a somewhat rapid rise with a slower fall in later years. The closeness of the curves for the two sexes is indeed remarkable, and is quite different from experience in England and Wales. In the West Indies young women expect to become pregnant in their early teens, and one would have thought that the strain of adolescence combined with that of early and many pregnancies would have raised the curve for females considerably higher than that for males. The closeness of the two curves to each other may be related to the open air life led by both sexes of all ages. The rates for each sex, arranged in decades, are shown in Table VI and Figs. 1 and 2. AVERAGE OF:
_._.-
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Tuberculosis death rates by age groups (females) between 1857 and 1956.
Males There is the usual high mortality in the very early years met with all over the world. The age group 5-9 years has always been one with a minimal mortality, but thereafter, with the onset of the strain of adolescence, the rate rises rapidly. At ages 25-54 the figures show a curve of the adult plateau type with high rates up to 8 per 1,000 in some age groups for the first two decades of the century under review, twice the England and Wales maximum for 1851-60 at age 25-34 years; this fell to a moderately steady 3-4 per 1,000 throughout the next five decades. From 1927 onwards the most characteristic feature of the curves is the great fall for each decade, though the peak remains at 25-34 years of age. During the last three decades, along with the fall in the rate at ages in early and middle adult life, the plateau type of curve has changed to one with two peaks, a main one still at 25-34 years of age, and a lesser one at 45-54 or later. In the age group 55-64 years the male mortality is higher than that for fenales. The numbers of the population aged 65 and over are small and it would be unjustified to draw any conclusion other than to state that the disease is present into extreme old age.
451
TUBERCULOSIS IN ANTIGUA TABLE VI.-TUBERCULOSIS IN ANTIGUA
Mean annual mortality per ],000 living at various ages, in quinquennia up to age [4 years, in decennial periods thereafter MALES Age
0-4 5 - 9 10-14
1857 1862 1867 1872 18771882188718921897190219071191211917 192219271932193719421947 1952 -61 -66 -71 -76 -81 -86 -91 -96 -01 -06 -11 -16 -21 -26 -31 -36 1--41 --46 -51 -56
- - -- - - - - - - - - - - - - - - 1-6 [,4 2-6 0'8 2'8 6·1 4·2 2-9 1-6 2·4 1'7 [,0 N 0'6 10:31-0.5 0·3 0·06 - - - ------ -- - - - -- j - - 0'8 0·2 0·8 0'2 0·7 0·5 0'7 0·4 0'3 0'2 0'2 0·2 0·3 0'3 0·2 l().l 0,[ D,] --- - ---- - ],0 I
0·7 0·2
H
0'8 0·8 H
['4 0·7
- -- -- -
0'3
o:s
I
--I- I
0-3 0'3 0·2 0'5
0,]
-,----:-
[5-24
4·3
3·7
3'2
2·9
2·5
J ·9
J ·9
J ,2
25-34
6·9
6·5
4'5
4-0
3·7
3'3
2-9
2'2
0'[ 0'5 0'3
! 0'9
0·4
1-6
],0
--35-44
6·5
6·4
3·7
~'7
3-9
2'8
45-54
8·0
6·4
4·2
3·7
3·2
2·7
55-64
8·2
5-8
3·0
H
2-3
65-74
5·6
4'5
2·2
J ·3
1'8
3·J
0·8
J·2
0·7
2·0
0·6
1-3
1-3
],7
1'1
J·5
rr
r-o
0·6
0·6
r-s
0·8
0·2
I
1862 Cohort FEMALES Age
185718621186711872187718821887 1892118971190211907 19121917 192211927 1932193719421947 1952 -61 -66. -71 -76 -81 -86 -91 -96 -01 -06 -11 -16 -21 -26 -31 -36 --41 --46 -51 -56
i J·O
i
0-4
2·J
5 - 9
0'9 0·2 0·8 0'31 0'7 0·5
10-14
3·3 0·9
['8
5·J
3'714'2 1-6 1-8 ]'5 J'2
l-81~'7
0·2 0'[
0'[
~
0·4 1·3 0'61 0'6 0'4 0-7 0'8 0·2 0-2 0'3 0·2 0'3
-
~~O~!OqF~~~~~O~OqO~O~~().l().l0:3~
-------------,-----------------
15-24
6,'
25-34
8·1
35-44
7 '1
I
s-s
Jo2
,.,
3"
6·5
4·9
4-4
4·0
7-l
3'7
4·2
2·4
I
2'4
a-s
1'6
'4
0,'
3'2
3·9
2·2
1'5
0'5
3-4
3,]
2'6
0·8
H
0'7
3']
3-8
2-6
1·5
0·9
0'8
0·9
2-3
2'0
],6
0·7
0·7
0·5
2'5
0·5
0·7
0'8
0,3
I
I 45-54
6-J
6·3
55-64
6·8
4'5
65-74
3·7
2·6
I
I I
I I 1
]'8
j'7
I I ,
I
J '8
,
I
I
0·6
0·5
I
•
1862 Cohort
452
TUBERCLE
Females The minimum mortality is at ages 5-9 years, though this is usually higher than that for males of the same age and decade. Then follows the group aged 9-14 years, again somewhat higher than its fellow in the male series. The age group 15-24 shows the rapid rise characteristic of the mortality of the disease at this age throughout the world; the value for each decade is either the same as or higher than its fellow in the male series. As in the case of the males, the curves for females in the first two decades of the hundred years are very high, though they fall more rapidly with age. During the decades 1877 to 1926 the curves for females resemble closely those for males in the same years, likewise being at a much lower level than in the period 1857-1876, the curve for each decade being lower than its predecessor. The curves for the last three decades form a unit, as with the corresponding ones for males, being the lowest for the century, with each decade being an improvement on its predecessor. The peak mortality at 25-34 years of age tends to be higher than the corresponding one for males. In extreme old age the tendency is for the female mortality to fall more consistently than in the case of males. There has been no shift in the peak of maximum mortality to older age groups in either sex in Antigua, such as has occurred in England and Wales and elsewhere in Europe. In Table VII the crude death rate from tuberculosis at ages for the first three decades is followed by similar information about the last three decades under review, in order to bring out clearly the the change that has taken place. During the first three decades there was a slight preponderance of mortality among females up to the age group 35-44, since when there has been a definite male preponderance. This male preponderance may be due to the large number of older men living by themselves under unsatisfactory conditions, a manner of living common in the West Indies. The lower ratio in the earlier decades in women of child-bearing age is almost certainly due to the stresses of pregnancy, more especially as pregnancy does not involve any cessation of manual work for more than a very few weeks. Why the ratio in the whole population has changed in recent decades is not so easily explained, but a possible reason is that men's living and working conditions may have improved faster than have those of women. COHORT ANALYSIS
By the term cohort is meant the survivors at any age of all persons born in a given year or group of years. The material for such an analysis can be obtained from tables such as Table Vl, which gives the mean annual mortality per 1,000 living at ages, but the grid must be traversed diagonally TABLE VII.-RATIO OF MALE TO FEMALE MORTALITY FROM TUBERCULOSIS AT AGES PER 1,000 LIVING
Age group (years)
Ratio of male to female mortality
1857-1886
1927 -1956
05 -
0·98 0'89
1'57 0·60
15-
10-
0'83 0'82
1·75 0'71
2535-
0·92 0·92
1'14 1·04
4555-
1'26 ',30
1·23 1·89
6575-
1-54 '-94
J ·61 0·24
453
TUBERCULOSIS IN ANTIGUA
(not verticall y) so as to ensure that each successive square shows a mortality rate derived fr om the survivors of those in the previous age group. In the table referred to, the identifying birth date of each cohort will be that of the central year which will provide five years of life experience to the quinquennium block, (or ten years to the decennium , as the case may be,) and will not appear in any contiguous cohort. The cohorts for Antigua show that the age of maximum mortality is always 25-34 years of age in males, and usually so in the case of females , with a steady fall in each sex to old age. This corresponds with experience in England and Wales. (Springett 1950). The tendency for the peak of the adult female mortality curve to mo ve back in recent years from the age group 25-34 years to that of 15-24 years, (as is the case also in England and Wale s.) indicat es some fundamental change in the age distribution of mortality, to the disadvantage of the female . Such a change has not taken place in the male. Apart from this, the general uniformity of the falls of the cohort mortality values is an indication that violent changes have not occurred in the mortality from tuberculosis of the negro in Antigua since the time that records have been kept. The main change is essentially one of a steady reduction in the mortality at all ages, - probably due to a slow elimination of the ope n type of pulmonary tuberculosis, such as is also occurring in Europe and North America. This more constant dist ributio n over the age of fifteen years in the cohort, as opposed to a tendency for a rise to occur in the decennial values, i.e. when the table is read from above downwards, implies that the mortality of a group in later life is to a cons iderable degree determined by conditions in infancy and childhood. The absence of a shift in the peak of the cohort mortali ty in either sex from 25-34 years of age to older age groups confirms experience in England and Wales and the more populous areas of Europe. The changes taking place over the years in the cohorts in Antigua can be seen in Ta ble VIII, where the mortalities at various ages have been expressed as a percentage of that at age 25-34 years in the same co hort. The infancy and early childhood rate was low until the decade of severe d ro ughts and economic depression, 1887-1896, since when the rate, as in England and Wales, has been much higher than that for the age group 25-34 years. I am unable to offer any explanation for the low figures before 1887. Apart from the rate in infancy, the table also shows a very constant type of mortality curve for each decade. In this respect it resembles similar cohort tables for England and Wales, with the maximum almost always in the 25-34 year age group . TABLE VIII.-MoRTALlTY AT VARIOUS AGES, AS A PERCENTAGE OF THAT AT AGE 25 - 34 YEARS IN THE SAME COHORT. COMBIN ED SEXES
Cohort
Age group
0-
5-
1827 - 36 1837 - 46
15-
25-
35-
45-
55-
65-
75-
81
100 100
90 57
42 51
38 33
30 8
11 4
II
1847 - 56 1857 - 66
39
18
80 71
100 100
84 85
75 63
35 19
26
16 19
1867 -76 1877 - 86
53 47
18 21
83 99
100 100
78 89
44
24
26 26
21
23
1887 - 96 1897 - 06
124 118
24
68 103
100 100
22
28 47
19
24
1907 -16 191 7 - 26
121 196
31 31
94 157
100 100
43
I7
57
8
454
TUBERCLE
Figs. 3 and 4 show that cohort values for succeeding decades have fallen considerably and very consistently. In my opinion it is reasonable to infer from the early ones that not only adult mortality rates were very high in the second quarter of the nineteenth century, but that in all probability so were those for infants and children. The early curves have the characteristics associated with a severe epidemic, with the serious phase of the epidemic ending soon after the turn of the century. I suggest that the cause of the epidemic was the liberation of the slaves in 1834. While the slaves lived and worked on thinly populated estates in considerable isolation from their fellows elsewhere,
7
6 V)
UJ
:ce 5 ~
o
04
Q
a::
UJ
c,
UJ3
!c(
a:: I
~2
1662
UJ
o
1622
1642
1--I---I--+---+----+----1----t----j
1662
;:t 1 Lf)
..0
AGE IN YEARS Fig. 3 Tuberculosis mortality by cohorts (males). (For clarity the cohorts for alternate decennia only are shown.)
there could be but few chances of becoming infected with tubercle bacilli, and those infected would therefore in the main be the 'non-immune'. As soon as the slaves were liberated they went to live in newly created, large congested villages, where the spread of the disease, once introduced by an open case, would be rapid among a susceptible community. The high death rates at ages 15-34 years in the two decades immediately following 1857 were in those who as infants were taken by their parents at the liberation of the slaves from the estates to live in the villages. Young nonimmune mothers in the 1830's and 1840's contracting tuberculosis for the first time under these conditions would quickly become infectious themselves, resulting in a major epidemic that spread rapidly through all ages, not only in infants and children, and was only slowly followed by a decline in severity. On comparing the cohort tables for England and Wales, and those for Antigua one is struck by
455
TUBERCULOSIS IN ANTIGUA
the similarities rather than the differences, and with the inevitable conclusion that similar factors must have been playing their part in influencing the mortality from tuberculosis in the two localities. In other words, the congestion caused by the industrial revolution in England and Wales led to an epidemic of tuberculosis in the mid nineteenth century; similarly, the liberation of the slaves in Antigua produced a severe outbreak of the disease about the same time for similar reasons. It makes one wonder whether too much emphasis may have been placed on race in the past as being an important factor influencing mortality.
8
7
Vl LJ..I
b
~ ~
0
5
o
Q 0::4 LU 0-
w 1-
;23 I
~
w
°2
'-'<----1922
1862 1842 1882
o:::tI I Q
l1"i
~ I !£2
'
"r If) N
'
V If) n
-e-
l1"i I
l1"i
'
"J-,
'
..0
'I
Lf)
..0
If)
AGE IN YEARS Fig. 4 Tuberculosis mortality by cohorts (females). (For clarity the cohorts for alternate decennia only are shown.)
Discussion It is evident that in Antigua, as elsewhere in the world, many factors are involved in preventing a more rapid fall in the mortality from the disease - poverty, bad housing, an unbalanced diet with its resulting poor health, night time overcrowding, and the presence of slums, But I have been impressed with the views of older experienced physicians, e.g. Cory (personal communication), who were certain that in Jamaica thirty years ago the disease as met by them was a much more rapidly advancing and fatal condition than it is today, quite apart from the more favourable prognosis now possible by the use of modern drugs. Living conditions in Jamaica have not improved F
456
TUBERCLE
sufficiently for them to be an important factor in this improvement. The same remarks apply to Antigua. Nevertheless, the mortality in Antigua has improved very much during the last half century and is now comparable with that of England and Wales a decade or two ago. This improvement is due to a slow but steady change in social and economic conditions, and the development of a relative immunity in the population following the high prevalence of the disease over the last 150 years, with the gradual elimination of the more susceptible. Certain causes that are often advanced as reasons for a fall in the rate do not apply to any great extent, such as a reduction in the size of the family, which is as large in Antigua as it ever was, nor to education, since any improvement in this field was of litt1e note until after the last war. A school health service is still practically non-existent, and infant welfare work began only ten years ago. The conditions of work have changed very little over the century, the peasant workers farm in the main in the same way as did their grandparents, even when a tractor does the rough ploughing or hauling for them. As regards the therapeutic factor of new drugs, this was of no significance until ten years ago. This paper is one of a series by the author dealing with the epidemiology of disease in the negro in Antigua, assisted by a grant from the Standing Advisory Committee for Medical Research in the British Caribbean, for which the author wishes to express his grateful thanks. REFERENCES COCHRANE, E. (1938). Tubercle, Lond., 19, 403. CROCKET, J. (1933). J. State, Med., 41, 164. GILMOUR, W. S. (1944). Caribbean med. J., 6, 171. JAMESON, W. W., & PARKINSON, G. S. (1952). A Synopsis of Hygiene, 10th edition, edited by L. Roberts and K. M. Shaw, p. 89, J. & A. Churchill, London. MINISTRY OF HEALTH (1952). Report of the Ministry of Health for the Year 1951. Part 2. On the State of the Public Health, p. 202, H.M.S.a., London. MINISTRY OF HEALTH (1958). Report of the Ministry of Health for the Year 1957. Part 2. On the State of the Public Health, p. 268, H.M.S.a., London. Sl'RINGETT, V. H. (1950). J. Hyg., Camb., 48, 361. WILCOCKS, C. (1932). E. Afr. med. J., 9, 88. YERUSHALMY, J. (l946). Publ. Repts, Wash., 61, 251.
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