An inter-racial study of the prevalence of hypertension in an urban South African population

TRANSACTIONS OFTHEROYALSOCIETY OFTROPICAL MEDICINE ANDHYGIENE, VOL.76, No. 1,

An inter-racial

study

1982

of the prevalence of hypertension South African population

in an urban

Y. K. SEEDATAND M. A. SEEDAT Dept. of Medicine,

University

of Natal,

Summary

This study was done to compare and contrast the prevalence of hypertension in the three racial groups of Durban, namely the Africans (Zulus), Indians and Whites, and was a random house-to-house study of 1,000 of each group. The prevalence of hypertension according to World Health Organization (WHO) criteria was highest in the African (25%), intermediate in the White (22.8%) and lowest in the Indian (19%). Age-corrected prevalence rates were: African 25%, Whites 17.2% and Indians 14.19%. Prevalence of hypertension was more common in females than in males in the African and Indian population, unlike the Whites. In all racial groups the mean arterial pressure rose with age. Unlike the White study, African females between the agesof 35 and 40 years had a higher prevalence than males. There was an association between hypertension and diabetes mellitus in the Indian nonulation. This studv showed that all three populatibn-groups had hyperiension which was undiagnosed, undetected or inadequately treated. The high prevalence of hypertension in the White and Indian population could explain the high incidence of ischaemic heart disease(IHD) in South Africa. In the African population, whilst they are spared IHD, hypertension is a major factor for the high incidence of cerebrovascular episodes. The lower prevalence of hypertension in the rural Zulu population and the difference in the years of residence between the hypertensive and normotensive urban Zulu suggests that urbanization plays an important part in the aetiology of hypertension in the Zulu. introduction

In South Africa, hypertension in the urbanized African is an emerging disease increasing in incidence. Studies of hypertension in hospitalized urban African patients have been described previously (SCHRIRE,1959; SEEDAT& REDDY, 1974). In 1975 we began-astudy of hypertension among the African, Indian and White DoDulations in Durban because there had been no gdkquate studies on the various racial groups. There is possibly no other country in which races are segregatedso distinctlv and in which socio-economic diiife&nces rest so clearly on colour (HORELL et al. 1977). Because of the inter-cultural differences we belie&d that this study would provide a good opportunity for observing the prevalence of hypertension among the three racial groups. Subjects

Durban,

Republic

of South Aftica

occupied predominantly by Zulus with a’few Xhosas and Basutos. In 1976 Durban had a population of approximately 400,000 Indians and 217,000 Whites (SOUTHAFRICA, 1976). In the sample populations, 1.000 Africans were randomlv examined between dctober 1975 and September’ 1976, 1,000 Indian subjects between August 1976 and July 1977, and 1,006Whites between November 1977and December 1978. There was a 99% confidence level with 5% tolerated error due to clustering for the randomization of this study (HANSEN& HURWITZ, 1951; BACKSTOM & HURSH, 1963). In all three studies the areas concerned were divided into blocks and the street at the end of each block was chosen. One in every three homeswas selectedand the adult answering the knock on the door was chosen as a subject. In the African study men’s hostels were included and one person in every third room was chosen for the study. The age span of the sample population ranged between 15 a;d 90 vears in all three studies. The most effective hours for- this door-to-door study were found to be weekends for African males, weekdays for Indian, African and White females and weekends and evenings for White and Indian males. This was a method of obviating the difficulty that people found at home $rFm;he day were different from people not found Due to social prejudices and because of the segregatedtownships for the various racial groups in South Africa it was necessary to have an observer from the racial group under study. There was a degree of between-observer agreement when measuring the same subjects. However it is possible, though less likely, that the different observersmeasuredthe blood pressure differently. There was one observer for a racial group and the three observers were qualified nursing sisters who had been trained for four weeks to take accurate blood pressure readings, as recommended by WHO (1962), and to interview subjects for possible factors predisposing to hypertension by means of a standardized questionnaire. Spot checks were carried out in all three studies to ensure that the study was being properly carried out. Febrile or physically or mentally distressed subjects were excluded. Blood pressurewas taken with a uroDerlv calibrated aneroid sphygmomanometer (cuff-length-53 cm and cuff width 14 cml. The examination of. and the interview with, eaih subject lasted for appioximately one hour. During the interview three casual blood

and Methods

In 1975 the African population in Durban was 375,000 of whom 200,000 (53%) resided in Umlazi, 150,000 (40%) in Kwa Mashu and 25,000 (7%) in Lamontville. These three large residential areaswere

Address for correspondenceand reprints: Prof. Y. K. Seedat,Dept. of Medicine, University of Natal, P.O. Box 17039, Congella 4013, Durban, Republic of South Africa.

Y.

K.

SEEDAT

AND

pressure readings were taken at minute intervals after the subject had been sitting and relaxed for at least five minutes. The pressure cuff was applied snugly to the bared unrestricted arm 2 to 3 cm above the antecubital fossa and sunported at the level of the heart at an angle of 45” away from the trunk. The cuff was raoidlv inflated to 20 to 30 mm Ha above the point at which the brachial artery was >bliterated. Cuff pressure was allowed to fall at a rate of not more than 2 to 3 mm Hg per pulse beat, and the point of first appearanceof an audible pulse beat was recorded asthe systolic pressure. The systolic and diastolic (4th phasemuffling of the sounds and 5th phasedisappearance of sounds) were recorded by the auscultatory method. The 4th phase was taken as the diastolic blood pressure. Hypertension was defined as a systolic pressure of 160 mm Hg or more, or a diastolic pressure of 95 mm Hg or more, or both. Readings were recorded to the nearest 5 to 10 mm Hg gradation below the observed figures and taken in both arms. The pulse, height (without shoes) and body weight (with minimal clothing) were recorded. Correction for arm girth was not done because (based on several studies) it was found that arm girth did not distort the measurementof blood pressure as long as the cuff was long and wide (EPSTEIN, 1979). Urine from all subiects was tested for albumin and sugar. Subjects found to be hypertensive were either referred to the hospitals or their general practitioners. Hypertensive subjectsin all three studies were further examined to exclude a secondary cause for hypertension. The results were negative.

M.

A.

63

ScEDAT

-

170

..

150

13 P g

110 1

30’

I 10

I 20

30

40 Age

50

!30

70

4 80

in years

Fig. 1. Mean systolic and diastolic blood pressures of male urban Africans, Indians and Whites.

-.-

0s

,&am

Whites

//

17

so-

Results

The WHO definition of hypertension (WHO, 1962) was used, namely, a systolic-blood pressure equal to or areater than 160 mm He and/or a diastolic blood pressure equal to or great& than 95 mm Hg in a subject over 30 years. For subjects under 30 years the values were taken at 150 mm Hg or more systolic and/or 90 mm Hg or more diastolic; for subjects over 65 years corresponding figures were 165 mm Hg or more systolic and/or 95 mm Hg or more diastolic. The age distribution of the three sample populations was similar to the age distribution for the South African population (SOUTH AFRICA, 1976). In the Indian study subjects were classified ethnically according to the data of Mistry (MISTRY, 1965). The prevalence of hypertension was lower in the Muslim than in the Hindu male population and this difference was statistically significant (pOeO5).

r" 130E .E llO2

_ w-

70-

Age in years

Fig. 2. Mean systolic and diastolic blood pressures of female urban Africans, Indians and Whites.

The mean systolic and diastolic blood pressure with standard deviation by ageand sex for the three studies are shown in (Tables I to IV). Mean systolic and diastolic blood pressure of male and female urban Whites, Africans and Indians are compared in Figs. 1 and 2. There was no statistical difference between blood pressure readings in the two arms, or between pulse rates in the hypertensive or normotensive groups in either the Whites, Africans or Indians. According to WHO criteria (1962) the orevalence of hypertension in urban Whites was 22.76% (males 25.6%, females 20-O%), in the urban African 25% (males 23%, females 27%) and in the urban Indian.

100

%

Number

70 91 78 56 62 39 46 29 25 15 13 7 4

535 100

Age

15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75+

Total %

14.6 i0.i 12.7 18.3 15.0 16.8 17.1 18.9 18.5 18.4 191 193 20.0

SD

69.93

321

37 73 50 39 35 30 22 15 9 5 4 1 1

t90

13.29

61

2 3 10 4 9 5 12 5 3 2 4 1 1

90-94

64.0 66.2 72.0 77.1 81fl 83.4 90.9 96.6 92.2 90.7 w5 95.2 101.0

Mean

SD

12.5 13.6 13.8 190 17.3 23.6 16.5 19.0 15.2 14.9 13.7 12.5 5.4

364 68.0

65 84 67 41 38 24 17 9 9 3 3 4 0

190

ZUlU

71 13.3

4 6 6 10 10 4 10 4 7 5 3 2 0

90-94

95-109

63 11.8

1 1 5 4 9 7 12 6 4 5 5 1 3

4.14

19

1 0 0 1 1 2 4 4 4 1 1 0 0

110+

loo

476

35 50 53 49 63 40 38 35 42 28 19 13 11

Number

and White mak

37 69

0 0 0 1 5 4 7 10 5 2 2 0 1

110+

524 100

13 51 71 77 65 56 58 48 38 31 9 3 4

Number

Indian and White female

12.64

58

2 2 9 5 7 11 6 6 5 3 1 0 1

95-109

blood pressure in the urban African,

459

Total

Table II-Diastolic

78.5 74.2 796 82.9 83.6 83.8 84.2 867 84.7 83.1 80.0

69 49 52 48 44 30 21 II 10 2 3

fifi.0

3.;

;il

42

Mean

mu

blood pressure in the urban African lodkn

15-19 __ __ 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75+

Age

Number

Table I--Diastolic

61.5 65.8 67.4 7@1 74.3 79.2 81.5 89.0 84.9 84.1 83.0 86.3 89.3

Mean

65.1 64.9 71.1 73.8 75.5 75.9 81.9 82.6 83.0 82.4 83.5 84.1 81.6

Mean

8.9 10.5 99 11.1 11.3 15.7 14.7 14.9 11.9 13.8 15.2 18.9 6.3

SD

10.6 9.4 10.7 10.9 13.5 12.4 13.4 10.4 14.8 14.4 12.9 17.2 6.4

SD

407 77.7

1

13 49 69 69 55 42 40 22 20 19 ;

~90

Indian

79.83

380

35 49 50 42 51 32 26 20 27 18 12 9 9

<90

Indian

44 8.4

0 2 2 4 7 2 5 3 9 7 1 0 2

90-94

8.19

39

: 4 4 9 3 3 2 0 1

0 0 3

90-94

48 9.2

16 7 2 1 0 1

8 8

0 0 0 3 2

95-109

987

47

0 1 0 1 6 3 7 6 9 5 5 3 1

95-109

25

48

0 0 0 1 1 4 5 7 2 3 1 1 0

1lOf

2.10

10

0 0 0 0 2 1 1 0 3 2 0 1 0

110+

503 100

37 60 57 62 51 55 39 36 35 28 22 13

8

Number

100

487

19 73 71 54 47 26 23 25 39 44 28 23 15

Number

70.3 73.5 73.5 77.8 77.3 79.0 83.4 85.9 83.8 88.2 90.9 86.7 86.3

Mean

76.3 78.7 80.9 83.5 81.4 84.0 83.3 86.9 90.9 88.9 85.9 82.1 89.9

Mean

7.5 12.7 10.9 10.5 10.7 97 11.1 15.2 11.9 14.4 19.2 13.3 10.9

SD

7.9 10.9 8.9 92 9.2 13.8 10.5 12.3 12.5 12.5 12.9 9.7 18.5

SD

383 76.1

34 56 48 53 45 38 23 22 20 17 13 6

8

<90

white

69.2

337

17 55 59 37 36 17 16 14 16 26 18 19 7

<90

White

49 9.7

7 4 4 4 4

8

0 1 1 5 5 1 5

90-94

12.1

59

3 3 4 7 6 1 1 0

8

2 10 5 9

90-94

45 8.9

0 1 3 3 2 4 11 4 5 6 1 2 3

95-109

14.9

73

3 6

8 8

7 7 2 4 3 5 12

8

0

95-109

26 5.2

0 1 0 1 2 1 1 4 2 5 6 3 0

110+

3.7

18

: 1 2 4 4 1 0 2

0 0 0 1

110+-

8

2

$

s

-_ 2

535 100

Age

Total %

Number

Table

4

IV-Systolic

%

70 91 78 56 62 39 46 29 25 15 13

459 100

Total

15-19 20-24 25-29 30-34 35-39 40-44 45-49 .50-54 55-59 60-64 65-69 70-74 75+

42 78 69 49 52 48 44 30 21 11 10 2 3

Number

AS

IS-19 20-24 25-29 30-34 35-39 40-44 45-49 SO-54 55-59 60-64 65-69 70-74 75+

III-Systolic

Table

101.9 107.0 110.0 121.6 124.4 129.3 137.3 156.0 147.2 148.2 158.9 166.2 182.5

Mean

blood

105.5 115.4 120.0 117.2 122.6 123.6 127.7 1309 140.7 132.3 145.2 147.8 175.0

Mean

blood

53 11.6

349 76.0

3 4 5 8 4 8 12 3 3 3 2 0 0

55 LO.5

65 87 72 42 44 20 21 9 8 5 1 6 0

380 71.0

13.7 13.5 16.2 24.6 24.9 34.2 26.5 35.7 27.5 26.0 37.8 32.2 17.0

140-149

~140

SD

ZUlU

African,

17 3.7

I 4 10 4 7 7 6 4 5 2 2 0 1

32 5.9

2 0 0 3 5 4 6 3 5 2 2 0 0

150-159

in tbe urban

1 4 10 4 7 7 6 4 5 2 2 0 1

African,

150-159

urban

140-149

Zulu

in the

39 73 57 40 41 34 31 18 8 5 2 1 0


pressure

16.5 14.7 15.5 25.0 23-O 22.1 22.4 30.4 34.1 22-5 22.9 21.8 25.0

SD

pressure

25 4.7

0 0 I 1 5 3 1 5 3 2 3 0 1

160-169

Indian

16 3.5

1 0 0 2 1 2 2 4 0 1 3 0 0

160-169

Indian

524 100

43 8.0

Number

female

476 100

35 50 53 49 63 40 38 35 42 28 19 13 11

Number

male

: 1 3

White

White

13 51 71 77 65 56 58 48 38 31 9 3 4

0 0 0 2 4 4 6 9 6

170+

and

24 5.2

0 0 0 1 3 2 3 3 7 2 2 0 1

170+

and

102.6 1062 107.0 110.3 116.1 127.6 134.4 1493 142.3 144.9 157.4 163.0 183.0

Mean

107.2 110.0 113.1 113.6 117.2 115.8 121.4 129.3 136.2 139.1 139.8 1699 153.9

Mean

10.9 15.3 11.9 18.7 18.2 27.6 26.2 31.1 24.5 29.1 44.6 22.9 33.4

SD

12.1 12.9 12.4 13.7 14.8 17.9 17.3 16.2 23.1 28.1 23.9 45.6 23.9

SD

388 74.1

12 48 70 72 58 42 36 16 20 10 3 0 1

<140

0 0 0 0 2 3 6 7 3 10 1 0 0 32 61

34 6.5

150-159

24 5.0

0 I 0 1 3 2 I 3 5 4 2 0 2

150-159

0 2 1 2 3 1 5 8 5 5 1 1 0

140-149

45 95

0 2 3 2 2 3 4 7 8 7 2 1 4

140-149

Indian

369 77.5

35 47 50 46 57 34 31 24 22 10 8 4 1


Indian

25 4.8

0 0 0 1 1 4 4 7 4 0 3 1 0

160-169

17 3.6

1 2

0 0 0 0 1 0 2 1 2 :

160-169

45 8.6

1 1 0 2 1 6 7 10 7 5 1 1 3

170+

21 4.4

0 0 0 0 0 1 0 0 5 4 2 7 2

170+

97.3 109.; 108.5 111.7 109.9 115.5 125.4 131.1 138.3 148.9 154.0 153.6 151.2

8 3; 60 57 62 51 55 39 36 35 28 22 13 503 100

Mean

118.3 121.5 120.4 122.4 122.2 121.8 128.9 133.4 145.2 139.5 138.8 137.2 162.4

Mean

Number

487 100

19 73 71 54 47 26 23 25 39 44 28 23 15

Number

14.9 ii; 13.9 12.1 18.6 16.2 18.9 29.1 24.4 31.2 34.1 32.8 25.9

SD

15.3 14.8 11.9 13.8 12.2 15.7 16.6 18.5 24.8 22.5 22.4 22.2 22.2

SD

385 76.5

8 36 58 57 60 46 42 26 15 13 12 7 5

~140

340 69.8

16 59 62 48 41 22 14 16 14 21 13 12 2

<140

39 7.8

n 0 1 0 0 4 4 6 10 6 4 2 2

140-149

White

67 13.8

2 10 9 4 5 2 5 3 9 9 3 6 0

140-149

White

17 3.4

” 0 1 0 0 0 5 2 1 3 1 3 1

24 4.8

0 1 0 0 1 0 3 1 5 7 2 3 I

160-169

20 4.1

31 6.4

150-159

0 0 0 0 0 1 1 2 3 2 4 1 6

160-169

1 4 0 1 1 1 3 2 6 4 5 1 2

150-159

38 3.4

0 0 0 0 I 1 1 4 5 6 9 7 4

l70+

29 5.9

0 0 0 1 0 0 0 2 7 8 3 3 5

170+

66

INTER-RACIAL

STUDY

OF

HYPERTENSION

19% (males 15.3%, females 22.3%j (Tables V and VI). When the prevalence according to WHO criteria was corrected for age (the Indian and White distributions were corrected to the African distribution) the prevalence rates were Whites 17.2% (22.01% males and 13.08% females) and Indians 14.19% (11.18% males and 16.73% females). While the difference between the prevalence rates of the African and Indian and the African and White were significant (p
IN

SOUTHAFRICA Discussion

This study of the prevalence of hypertension in the three racial groups compared and contrasted the data and showed distinct differences. The prevalence of hypertension in the urban African (SEEDATet al., 1978), Indian (SEEDAT et al., 1978) and White (SEEDATet al., 1980) of Durban has been previously described. This study compares and contrasts the prevalence of hypertension among the three racial groups. In the urban adult African the prevalence :f hypertension was 25% (females 27%, males 23%) basedon WHO criteria (1962). This is similar to that in the American Negro; since the National Health Examination Survey (1962) provides data which indicate that 15% of Whites and 27% of Negroes have hypertension. Our urban African had higher mean blood pressure than the Whites of the USA (COMSTOCK,1957) and England (HAMILTON et aE., 1954). Our urban African females had higher mean blood pressuresthan did the White females of the USA and lower than the Negro females of the USA (COMSTOCK, 1957). The difference in the mean arterial pressure between the American Negro and the urban African is probably due to the American Negro having been accultured for 300 years whereas the urban African has been accultured only since the turn of the century. The mean systolic and diastolic pressure in our African study (SEEDATet d., 1978) were lower than those in the West Indian (MIALL & OLDHAM, 1963) and Nigerian studies (JOHNSON, 1971). It is possible that differences in the years of acculturation of the American Negro, West Indian, Nigerian and our urban African could explain the lower systolic and diastolic blood pressure in our urban African. Preliminary data of the prevalence of hypertension in our rural African show that it is 10% and not as high as our urban study, namely 25%. This lower prevalence rate of hypertension in the rural African population and the difference in the years of residence between the hypertensive and normotensive Africans suggests that urbanization plays an important part in the aetiology of hypertension in the African. Available data in Africa show that the prevalence rate in rural Ghana (POBEEet al., 1977), namely 4.5%, is not as high as in our urban study, namely 21*8%, if a systolic blood pressure of 160 mm Hg or more and/or a diastolic blood pressure of 95 mm Hg or more is taken as the criterion. In contrast, the rural Bushmen in the Kalahari Desert showed a lower mean systolic and diastolic blood pressure, no rise in blood pressure in males and only a slight rise in pressure in females with age (KAMINER & LUTZ, 1960). Our urban African females between the agesof 35 and 40 years have a higher prevalence of hypertension (25.8% females v. 13.4% males) and 39% of all African female patients were below the age of-40 years (Tables V and VI). The prevalence of hypertension in our urban adult White study of 1,006 subjects according to WHO criteria (1962) was 22.7% or 17.02% when corrected for aee (Tables V. VI. VII and VIII>. This orevalence rate was lower than in our urban AfricanLstudy but higher than our urban adult Indian study. Using the criteria of 160 nun Hg or greater systolic and/or 95 nun Hg or greater diastolic blood pressure we found that the prevalence rate in the Whites was

104

VI-Prevalence

5 II 18 7 16 15 21 16 15 7 9 3 4

147

Total

Table

20-24 25-29 30-34 35-39 4044 45-49 50-54 55-59 a64 65-69 70-74 75+

Total

3.4 7.48 12.24 4.76 10.88 10.20 14.29 10.88 10.20 4.76 6.12 2.04 2.72

COlUIM Percentage

of hypertension

2.88 8.65 18.27 5.77 6.73 12.50 1346 9.62 9.62 4.81 3.85 1.92 1.92

COlUIM Percentages

Number

3 9 19 6 7 13 14 10 10 5 4 2 2

of hypertension

V-Prevalence

IS-19 20-24 25-29 30-34 35-39 40-44 45-49 SO-54 55-59 60-64 65-69 70-74 75i

Age

Table

Zulu

535

119

0 2 2 7 6 13 20 26 19 15 5 1 3

female.

7.14 12.09 23.08 12.50 25.81 3846 45.65 55.17 6om 46.67 69.23 42.86 lOOal

White

70 91 78 56 62 39 46 29 25 15 13 7 4

and

73

7 8 8 7 12 12 5 7 3

0 2 1

NUlllblX

Indian

male.

Number

White

ROW Percentage

African,

and

Total

in the urban

459

7.14 11.54 27.54 12.24 1346 27.08 31.82 33.33 47.62 45.45 40.00 100.00 66.67

Indian

42 78 69 49 52 48 44 30 21 11 10 2 3

African,

ROW Percentages

urban

Total

in the

ZUlU

criteria

0.00 1.68 1.68 5.88 5.04 10.92 16.81 21.85 15.97 12.61 4.20 084 2.54

COlUlNl Percentage

criteria

om 2.74 1.37 1.37 959 lo.% lO.% 9.59 16.44 1644 685 959 4.11

Column Percentages

WHO

WHO

Indian

Indian

524

13 51 71 77 65 56 58 48 38 31 9 3 4

Total

040 3.92 2.82 9.09 9.23 23.21 34.48 54.17 5oaiB 48.39 55.56 33.33 75.00

ROW Percentage

040 4.00 1.89 2.04 11.11 2oal 21.05 20.00 28.57 42.86 26.32 53.85 27.27

35 50 53 49 63 40 38 35 42 28 19 13 11 476

ROW Percentages

Total

103

0 3 5 5 4 7 13 10 11 15 11 11 8

NUttlbfX

126

3 20 12 9 3 7 4 9 18 17 10 6 8

Number

090 2.91 485 4.85 3.88 6.80 12.62 9.71 10.68 14.56 10.68 10.68 7.77

Column Percentage

2.38 15.87 9.52 7.14 2.38 5.56 3.17 7.14 14.29 13.49 7.94 4.76 6.35

COlUlNl Percentages

White

White

514

8 37 61 57 62 52 55 40 36 35 30 26 15

Total

492

19 73 71 54 47 27 23 26 39 45 29 24 15

Total

,,

,.

040 8.11 8.20 8.77 6.45 13.46 23.64 25.00 30.56 42.86 36.67 42.31 53.33

ROW Percentage

15.79 27.40 1690 16.67 6.38 25.93 17.39 34.62 46.15 37.78 34.48 25.00 53.33

ROW Percentages

8

459

Total

Total

70 91

::

62 39 46 29 25 15 13 7 4

535

Age

15-19 20.24

25-29

30-34 35-39 40-44 45-49 50.54 55-59 60-64 65-69 70-74 75i

Total

VIII-Prevalence

42 78 69 49 52 48 44 30 21 11 IO 2 3

15-19 20-24 25-29 30-34 35-39 40-M 45-49 50.54 55-59 60-64 65-69 70-74 75+

Table

Total

VU-Prevalence

Age

Table

100

104

4.76 10.88 10.20 14.29 IO.88 10.20 4.76 6.12 2.04 2.72

7 16 15 21 16 15 7 9 3 4

100

12.24

18

147

3.40 7,48

5 11

Hypenensives

African,

COlUmn Percentage

Africans

in the urban

2.88 8.65 18.27 5.77 6.73 12.50 1346 9.62 962 4.81 3.85 1.92 1.92

of hypertension

Africaa,

GAumn Percentage

Africans

ia the urban

3 9 19 6 7 13 14 10 10 5 4 2 2

Hypmensives

of hypertension

and

and

2.82 909 9.23 23.21 34.48 54.17 5om 48.39 55.56 33.33 75.00 16.73

2.46 5.69 639 10.11 17.72 17,55 13.96 8.11 8.07 2.60 3.35 100

2.20 5.09 5.72 905 15.86 15.71 12.50 7.26 7.22 2.33 3.00 89.51

23.08 12.50 25.81 3846 45.65 55.17 6QTlo 46.67 69.23 42.86 10030 27.48

ROW Percentage

11.18

4.00 1.89 2.04 11.11 2om 21.05 2om 28.57 42.86 26.32 53.85 27.27

ROW Percentage

040 3,92

COlUUUl Percentage

Indians

age

100

608 2.53 1.95 11.27 18.71 18.05 11.70 11.70 9.18 5.13 2.11 1.60

COlUttlIt Percentage

Indians

090 3,99

for

age

040 3.57

Hyperetensives mcorrected)

comected

for

7.14 12,09

ROW Percentage

White

51.30

Hypertensives (agecorrected)

corrected

22.66

female

male

0 3.12 1.30 190 5.78 960 9.26 6.00 6.00 4.71 2.63 I.08 0.82

Indian

Indian

7.14 1;,;4 27.54 12.24 1346 27.08 31.82 33.33 47.62 45.45 4oal 10000 66.67

ROW Percentage

White

3 F 8.77 6.45 13.46 23.64 25.00 30.56 42.86 36.67 42.31 53.33 7.02 5.72 7.50 15.53 lo,36 10.92 9.19 6.82 4.23 3.04 100

491 4.00 5.25 IO.87 7.25 7.64 6.43 4.77 2.96 2.13 6999

13.08

r 8.20 914 6.40

2

8

2

ti

%

F

[

2

5

030 8.11

ROW Percentage

22.01

15.79 27.40 1690 16.67 6.38 25.93 17.39 34.62 46.15 37.78 34.48 25.00 53.33

ROW Percentage

woo 10.54

COhlttXl Percentage

Whites

100

6-56 21.15 11.54 8.09 3.29 12.32 7.57 10.28 9.59 412 3.41 0.49 1.58

COlUtlllt Percentage

Whites

040 7.38

Hypertensives (ap’ecorrected)

101.04

6.63 21.37 11.66 8.17 3.32 12.45 7.65 10.39 9.69 4.16 3.45 030 1.60

Hypertensives (agecorrected)

7.14 1000 1640 15.55 15.17 16.86 18.59 19% 21.02 21.62 22.03 22.37 22.66

IJercenrage

6

2

%

104

Therapy

No therapy

Total

Africans

92.31

1.92

5.77

Percentage

81

51

8

22

Indians

Males

62.%

988

27.16

Percentage

15.34

090 2.35 2.17 2.14 4.40 6.55 8.23 937 11.36 13.39 ,394 i;ii

Percentage

groups

126

3 23 35 44 47 54 58 67 85 102 112 118

Number

492

19 92 163 217 264 291 314 340 379 424 453 477

Total

Whites

25.61

15.79 25THl 21.47 20.28 17.80 18.56 IS.47 19.71 22.43 24.06 2472 24.74

Percentage

147

5 16 34 41 57 72 93 109 124 131 140 143

Number

535

70 161 239 295 357 3% 442 471 4% 511 524 531

Total

ZUIUS

27.48

7.14 994 14.23 1390 15.97 18.18 21.04 23.14 25.00 25.64 2672 26.93

PeICCIWgC

121

95

10

16

Whites

78.51

8.26

13.22

Percentage

147

120

12

15

Africans

81.63

8.16

IO.20

Percentage

121

45

13

63

Indians

37.19

IO.7

52.07

Percentage

Females

92

50

10

32

Whites

54.38

10.78

3478

Percentage

lndian and White subjects known or found to be suffering from hypertension

476

.__

35 85 131 187 250 290 328 363 405 433 452 465

0

2 3 4 11 19 27 34 46 58 63 70 73

Total

Number

therapeutic situation in urban African,

42 120 189 238 290 338 382 412 433 444 454 456 459

X-The

Total

3 12 31 37 44 57 71 81 91 % 100 102 104

Therapy discontinued

Table

<65 <70 <75 >75

40

<20 <25 <30 <35 <40 <45 40 <55

Indians

M&S

hypertensives by age in the tbrec racial

ZUIUS

at

NUIIlber

l~-Comparison

Age

Table

251

216

14

21

Africans

119

0 2 4 11 17 30 50 76 95 110 115 116

NUd3.X

86.06

5.58

8.37

Percentage

524

13 64 135 212 277 333 391 439 477 508 517 520

TOtal

Indians

Females

202

96

21

85

Indians

22.71

030 3.13 2.96 5.19 kl4 901 12.79 17.31 1992 21.65 22.24 22.31

Percentage

47.52

1040

42.08

Percentage

103

0 3 8 13 17 24 37 47 58 73 84 95

Number

213

145

20

48

whites

514

8 45 106 163 225 277 332 372 408 443 473 499

TOtal

Whites

68.08

939

22.54

Percentage

20.04

o%fl 6.67 7.55 7.98 7.56 8.64 11.14 12.63 14.22 16.48 17.76 19a

Percentage

w

?F

l-2 :

70

INTER-RACIAL

STUDY

OF HYPERTENSION

19.6% (males 20.3%, females 19.11%) or 19.92% (22.66% males, 17.57% females) when corrected for age, and the urban Indian was 20.2% (females 23%, males 17%) or 20.32% (17.65% males, 23*62% females) when corrected for age. The prevalence of hvnertension in the urban White of Durban is higher than the 17% prevalence rate (males 18.5%, females 15.7%) which the United StatesPublic Health Service (1976) found in their representative sample of 17,796 Whites from 1971-74. In contrast to the urban Africans and Indians of Durban in whom hypertension was more common in females, hypertension was more common in our White males than in White females. Hypertension was more common in the urban African female compared to the urban White female under the age of 50 years (Table IX). The male:female ratio (2:l) under 40 years in our White study is almost similar to that for Whites in London (HAMILTONet al., 1954)in whom hypertension under 40 years is three times more common in males than in females and contrasts with the male:female ratio (1:1*07) under 40 years in the Indian study and the male:female ratio (1:l) in the African study. The mean arterial pressure in both male and female Whites rose with age, the rise being more marked in males over the ageof 40 years and in females over the ageof 60 years(Tables I to IV). The mean systolic and diastolic blood pressurewere higher in the male urban White than in the male African and Indian and lower than in the female African and Indian (Figs. 1 and 2). The mean systolic and diastolic blood pressuresin the Whites of Durban were higher than the Georgia Whites (COMSTOCK,1957) and lower than the Londoners (HAMILTON et aE., 1954). In the White subjects there was no difference in the prevalence of hypertension among the ethnic groups and between the immigrant and native White subjects. This suggestedthat the aetiology of hypertension was due to similar factors in their life style. The prevalence of essential hypertension in a random house-to-house study of 1,000 Indians according to WHO criteria was 19% (females 22%, males 15%) or 14.19% (males 11.18%, females 16.73%) when corrected for age (Tables V, VI, VII and VIII). The prevalence of hypertension in our Indian study was greater than published data from India. namelv greater than 10% in Bombav (DALAL et al., 1977), 15*& in Madras and 6.2% in-New Delhi (MALHOTRA, 1971), 0.17% in the lower socioeconomic group and 2.5% in the higher economic group of New Delhi (PADMAVATI& GUPTA, 1959) and 4.3% in Agra (MATHURet al., 1963). We found that Muslims had a lower prevalence of hypertension than the Hindi and this was significant at the 5% level. Among Europeans and Americans of Caucasian stock there is suggestive evidence of a familial tendency to hypertension (HAMILTON et al., 1954; MIALL h OLDHAM, 1963;‘ PLATT, 1963; AYMAN~ 1934: IOHNSONet al.. 1965). Becauseit was difficult to locale relatives of subjects suffering from hypertension it was not possible to record the blood pressure of relatives. A family history of hypertension among parents, brothers and sisters was obtained in 8% of the African hypertensive subjects, in 12% of the hvpertensives and 22% of the normotensives in White subjects and 38% of the hypertensives and 35% of the normotensives in Indian subjects. The difference in

IN

SOUTH

AFRICA

family history might be due to the fact that the White and Indian are more sophisticated, more health conscious and likely to be better informed on family illnesses and causesof death. The Whites and Indians in Natal have been urbanized for much longer and consequently have had accessto medical care of a higher standard than the Zulu who moved into Durban more recently and who, at least one generation ago, had little or no formal education and little accessto proper medical care. A family history of hypertension was more common in the normotensive compared with the hypertensive White. 90% of our Zulu patients had hypertension which was undiagnosed, undetected or inadequately treated (Table X). 58% of the Indian hypertensive patients and 77% of the White hypertensive subjects had hypertension which was untreated or had discontinued therapy (Table X). Thus it is desirable to have an effective therapeutic compliance programme. In conclusion, this study has important implications. A diastolic blood pressure 4 105 mm Hg was found in 3.9% of the Indian and 6% of the White subjects and a diastolic blood pressure < 110 mm Hg was found in 5% of the Zulu subjects. Casual blood pressure among Whites in England show up to 15% have a diastolic blood pressure < 105 mm Hg and this proportion falls to 3% if one takes three readings (BULPITT, 1979). The higher prevalence of diastolic blood pressure < 105 mm Hg together with the high prevalence of hvpertension in our White male subjects could be an important factor in the aetiology of II-ID. IHD in the White male in South Africa in the age group between 25 and 34 years is the highest in the world, being 23*1/1OO,OOO compared with9.3/100,000 in the USA (WYNDHAM. 1978). The hizh nrevalence of hypertension in the Indian and its asioc:ation with diabetes mellitus suggests that this is a significant factor in morbidity and mortality. This factor correlates with the higher mortality among the Indians in Durban compared with Whites in the 35 to 69-yearsold group, related to the higher incidence of hypertensive vascular disease and ischaemic heart disease (WAINWRIGHT, 1969). High blood pressure, raised serum cholesterol, cigarette smoking, overweight and diabetes mellitus were major IHD factors in the USA (KANNEL, 1961). In the African population the rarity of myocardial infarction in spite of the high prevalence of hypertension remains an enigma (SEEDATet al., 1978; SEFTEL, 1978). The higher prevalence of hypertension in Africans, particularly in females under 40 years, probably explains the younger age of hypertensive patients seen in African patients at autonsv. Death is usuallv from cerebral haemorrhaee (ISAACSON,1977). a Acknowledgements

This study was financially supported by the Medical Research Council of South Africa. We wish to thank Nursing Sisters: M. N. Nkomo, K. Reddy and M. Veale for doing the study. References

Ayman, D. (1934). Heredity in arteriolar (essential) hypertension. Archives of Internal Medicine, 53, 792-802. Backstom, C. H. Sz Hursh, G. D. (1963). Drawing the Sample. In: Survey Research. J. A. Robinson

Y. K.

SEEDAT

(Editor). Minneapolis: USA North Western University, p. 32. Bulpitt, C. J. (1979). An Epidemiological view of mild hypertension. In: Mild Hypertension. Natural History and Management. Gross, F. & Strasser, T. $E-lp). Kent, England: Pnman Medical, pp. Cornstock, G. W. (1957). An epidemiologic study of blood pressure in a biracial society in the Southern United States. American .7ournal of- Hygiene, 65, -217-315. Dalal, P. M., Shah, K. D. & Jhaveri, G. C. (1977). A communitv screening survev in “Old Bombav” Prefecture-a prelir&ary report. Abstract of International Congress on Hypertension, 7-9 October 1977, Bombay, India, p. 22. Epstein, F. H. (1979). Hypertension risk factors: A preventive point of view. In: Mild Hypertension. Natural History and Management. Gross, F. & Strasser, T. (Editors). Kent, England: Pitman Medical, pp. 127-138. Hansen, M. H. & Hurwitz, W. H. (1951). Modern methods in the sampling of human populations. American Journal of Public Health, 41, 662-668.

Hamilton, M., Pickering, G. W., Roberts, J. A. F. & Sowry, G. S. C. (1954). Aetiology of essential hypertension; role of inheritance. Clinical Science, 13, 273-304.

Horrell, M., Hodgson, T., Blignaut, S. & Moroney, S. (1977). Employment education in a survey of race relations in South Aftica. Johannesburg: South African Institute of Race Relations, p. 226. Isaacson, C. (1977). The changing pattern of heart disease in South African Blacks. South Aftican Medical Journal,

52, 793-798.

Johnson, B. C., Epstein, F. H. & Kjelsberg, M. 0. (1965). Distributions and familial studies of blood pressure and serum cholesterol levels in a total community-Tecumeseh, Michigan. Journal of Chronic Diseases, 18, 147-160. Johnson, T. 0. (1971). Arterial blood pressure and hypertension in the urban African population samole. British ‘fournal of Preventive Medicine, , 25.I 26-3-3.

-

-

Kaminer, B. & Lutz, W. I’. W. (1960). Blood pressure in Bushmen of the Kalahari Desert. Circulation. 22. 289-295.

Kannel, W. ‘B. ‘(1961). Factors of risk in the development of‘coronary heart disease-six year follow-up experience. The Framingham study. Annals of Internal Medicine, 55, 33-50.

Malhotra, S. L. (1971). Studies in arterial pressure in the North and South India with special reference to dietary factors in its causation. Journal of Association of Physicians of India, 19, 211-233. Mathur, K., Wahu, I’. N. & Gahlaut, D. (1963). Blood pressure studies in the adult population of Agra, India. American Journal of Cardiology, 11, 61-65. Miall, W. E. & Oldham, P. D. (1963). The hereditary factor in arterial blood pressure. British Medical Journal,

i, 75-80.

AND

M.

A.

SEEDAT

71

Mistry, S. D. (1965). Ethnic groups of Indians in South Africa. South Aftican Medical 7ourna1,_ 31,. 691-694. National Health Examination Survey (1964). National Center for Health Statistics. United States 19601962. Series 11, DHEW, Washington, D.C. Padmavati, S. & Gupta, S. (1959). Blood pressure studies in rural and urban groups in New Delhi. Circulation,

19, 395-405.

Platt, R. (1963). Heredity in hypertension. Lancet, i, 899-904.

Pobee, J. 0. M., Larbi, E. B., Belcher, D. W., Wurapa, F. K. & Dodu, S. R. A. (1977). Blood pressure distribution in a rural Ghanian population. Transactions of the Royal Society of Tropical Medicine and Hygiene, 71, 66-72.

Schrire, V. (1959). The racial incidence of heart disease at Groote Schuur Hospital, Cape Town. Part II. Hypertension and vascular diseaseof the heart. American Heart Journal, 56, 742-759. Seedat, Y. K. & Reddy, J. (1974). A study of 1,000 South African Non-White hypertensive subjects. South African Medical Journal, 48, 816-820.

Seedat, Y. K., Seedat, M. A. & Reddv, K. (1978). The prevalence of hypertension in- the Indian nooulation of Durban. South Aftican Medical joktal. 54, 10-15. Seedat, Y: K:, Pillay, N. & MarcoyannopoulouFojas, H. (1977). Myocardial infarction in the African hypertensive patient. American HeartJournal, 94, 388-390.

Seedat, Y. K., Seedat, M. A. & Veale, M. (1980). The prevalence of hypertension in Urban Whites. South African Medical Journal, 57, 1025-1030. Seftel, H. C. (1978). The rarity of coronary heart disease in South African Blacks. South African Medical 3ourd,

54, 99-104.

South African (1976). Population of South Africa 1904-1970,Dept. of Statistics, (Report No. 02-0512). Pretoria, Government House. Strasser,T. (1972). Pilot programmes for the control of hvnertension. World Health Organization Chronicle, 26, 45 l-455. United StatesPublic Health Service (1976). Advance Data from Vital and Health Statistics of the National Center for Health Statistics. No. 1. Rockville, Maryland, USA. Wainwright, J. (1969). Cardiovascular diseasein the Asiatic (Indian) population of Durban. South African Medical Journal, 43, 136-138. World Health Organization (1962). Arterial hypertension and ischaemic heart disease: preventive asnects. World Health Organization Technical Report Series, No. 231. Wyndham, C. H. (1978). Ischaemic heart disease mortality rates in White South Africans compared with other populations. South African Medical Journal, 54, 595-601.

Accepted for publication 20th May,

1981.