Stroke trends in Japan

Stroke Trends in Japan KAZUNORI KODAMA,

MD

In Japan, stroke now ranks third among all causes of death following cancer and heart disease. Stroke was the leading cause of death for 3 decades after 1951. Stroke mortality tended to increase until about 1970, but it decreasedand yielded first place to cancer in 1981. Heart disease deaths outnumbered stroke deaths beginning in 1985. There have not been any nationwide studies of stroke incidence in Japan, but results of studies in model ureas such as Akitu/Osuka, Nugano, Hiroshima/Nagasaki, and Hisayama show remarkable decreases in the incidence of cerebral infarction and cerebral hemorrhage. However, the decrease in cerebral infarction is less, especially at advanced ages where the frequency of disability is still high, and a major problem. There have not been any nationwide studies of survival rates after stroke either. In the Hiroshima/ Nagasaki Study, the cumulative surwival rates of cerebral hemorrhage and cerebral infarction improved from 1958 to 1969 to the period from 1970 to 1984. The decreasing incidence and mortality rates of stroke and the improving survival rate may be explained by the trends toward less severe strokes and improved medical service; however, the most influential factors are considered to be adoption of a less traditional life-style and improved blood pressure management throughout Japan. Ann Epidemiol I993;3:524-528. KEY WORDS:

Stroke, mortality, incidence, survival, trends in Japan.

The stroke incidence and survival data are obtained from

INTRODUCTION In Japan,

stroke ranks third among all causes of death,

following cancer and heart disease. In 1990, stroke deaths numbered

121,944, and accounted

for 14.9% of all deaths.

The number of patients with stroke was estimated at 377,500 in 1990, exceeding the totals for cancer and for heart disease (1). Therefore,

articles published in Japan and from the long-term follow-up study conducted by the Radiation Effects Research Foundation (RERF).

Information

on the prevalence rate of hyper-

tension and the utilization of medical services was obtained from the reports of Ueshima

and coworkers (3, 4).

stroke is still one of the most significant

diseases in Japan, although the incidence In this report, trends in the mortality,

is decreasing. incidence,

survival rates of stroke in Japan are described. Changes the risk factors that have possibly contributed crease of stroke are also described.

and in

to the de-

RESULTS Stroke

Mortality

According

to the Vital Statistics, stroke ranked first among

all causes of death for 3 decades after 195 1. Stroke mortality tended to increase until about 1970, but it decreased subsequently and yielded its first place to cancer in 1981. In 1985,

MATERIALS

AND

Most of the Japanese

stroke deaths were outnumbered

METHODS data mentioned

in this article are

based on vital statistics and the National Nutrition Survey. Sex-specific and 5-year age-specific mortality rates of stroke were obtained from the Vital Statistics of 1950 to 1990 (1). National

Nutrition

Surveys from 1955 to 1990 were used

to describe nutritional

changes (2).

by heart disease deaths

and stroke now ranks third among all causes of death (1). Trends in age-specific mortality rates for stroke in Japan are shown by sex in Figures 1 and 2. Stroke mortality started to decline about 1965 among men aged 50 to 69 years, and the rate of decline accelerated after 1970. The decline was less in the early years among 40s to 49-year-old men, but it accelerated after 1980. Stroke mortality started to decrease earlier in women than men for all age categories (1, 4, 5).

From the Department of Clinical Studies, Radiation Effects Research Foundation, Hiioshima, Japan. Address reorint reauests to: Kazunori Kodama, MD, Chief, Department of Clinical Studies, Radiation Effects Research Foundation, 502, Hijiyama Park, Minami-ku, Hiroshima 732, Japan.

Among the different types of stroke, cerebral hemorrhage showed the most remarkable decrease beginning as early as 1960, and continued downward in a linear trend until 1975. At this time, mortality from cerebral hemorrhage became lower than that from cerebral infarction. In

September

1993: 524-528

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Kodama STROKE TRENDS IN lAPAN

AEP Vol. 3, No. 5

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1000

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22

1

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1960

1950

I

1980

1970

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1990

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1. Trends in age-specific mortality from stroke for men 1950 to 1990 (Japanese Vital Statistics, 1950 to 1990).

but the proportion

fell to 31% in 1985. In contrast,

death rate for cerebral infarction infarction

Cerebral

accounted for only 3% of all strokes in 1951, but

for 50% in 1985 (1). Since death certificate information

in

Japan is less accurate for the type of stroke, more accurate information

FIGURE 2. Trends in age-specific mortality from stroke for women in Japan, 1950 to 1990 uapanese Vital Statistics, 1950 to 1990).

the

tended to increase until

about 1975, but it tended to decrease subsequently.

I_ 1990

480

Year

Year FIGURE in Japan,

ii70

that the anuual incidence of cerebral infarction was approximately three times higher in Japan between 1972 and 1978 than in Hawaii between 1965 and 1973 (10). The incidence of cerebral infarction

in Hiroshima

is now similar to that

in Hawaii during the late 1960s.

should be obtained from incidence studies (6).

Stroke Survival Stroke Incidence

There has not been any nationwide study of survival rates

Since there has not been a nationwide study of stroke inci-

after stroke. In the Hiroshima/Nagasaki

dence in Japan, the results of studies conducted

survival rates were compared for 1958 to 1969 and for 1970

at model

Study, cumulative

areas are described. Similar results were obtained in Akita/

to 1984 using the life-table method. Improvement

Osaka,

rate was observed

Nagano,

Hiroshima/Nagasaki,

and

Hisayama.

These studies showed a remarkable decrease in the incidence

hemorrhage

of cerebral hemorrhage

nificant

cerebral infarction.

and a decrease in the incidence of

However, the decrease in the incidence

of cerebral infarction

was less among persons of advanced

in the latter period for both

and cerebral infarction.

improvement

cerebral infarction Similar

in survival cerebral

Figure 4 shows a sig-

in the cumulative

survival rate for

in the latter period.

results were obtained

from the Akita/Osaka

age among whom the frequency of disability remains high

Study, Nagano Study, and Hisayama Study. Reduction

and continues

the case-fatality

to be a major problem (7-9).

in

rate was also observed in recent years.

Figure 3 shows the results of the Hiroshima/Nagasaki Study conducted at the RJZRF for 32 years. Age-adjusted incidence rates of cerebral hemorrhage and cerebral infarction declined in Hiroshima

Blood pressure is one of the most important risk factors for

in both sexes.

The age-adjusted incidence of cerebral infarction in men was 4.9 per 1000 person-years person-years

in

among Japanese

1988.

in 1972 and 1.2 per 1000

Comparison

of stroke

Blood Pressure

incidence

men living in Japan and Hawaii showed

cerebral hemorrhage

and cerebral infarction

(8, 11-13). In

Japan, both mean systolic and diastolic blood pressures have decreased since the mid 1960s for both sexes in all age categories (3, 4). The prevalence of systolic hypertension

(systolic

K&ma STROKE TRENDS IN JAPAN

AEP Vol. 3, No. 5 September1993: 524-528

-----Women

;I; TCh

60_6gyr

k

5 5

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3

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50-59yr

---,_,_,

40-49yr 0.1’

I..

.

1960

.

,

.

.

1970

, 1980

.

.

.

.

,

1956

I

I

1961

1966

1990

0

1971 Year

1976

1981

1986

Year

FIGURE 3. Trends in age-adjusted men and women in Hiroshima, Hiroshima/Nagasaki Study).

incidence from stroke for 1958 to 1990 (32~year follow-up,

blood pressure L 180 mm Hg) decreased after 1965; the decrease was greater after 1970 (3, 4) (Figure 5). A similar trend was seen in women. Dietary Factors Salt intake is an important factor influencing the level of blood pressure. Figure 6 shows the trend in per capita salt consumption in Japan based on the results of the National Nutrition Surveys (2). Salt intake declined from the mean intake of 14.5 g/person/d in 1972 to 11.7 g/d in 1987; but it increased thereafter and reached 12.5 g/d in 1990. Increased fat intake and a low ratio of polyunsaturated to FIGURE 4. Trends in cumulative farction Study).

by

period

FIGURE 5. Trends in age-specific prevalence of systolic hypertension (systolic blood pressure 2 180 mm Hg) for men in Japan, 1956 to 1986 (Japanese National Nutrition Surveys).

saturated fat are well-known risk factors for atherosclerosis because of their cholesterol-raising effect. On the other hand, moderate intakes of animal protein and fat are considered to be effective in preventing stroke (3). Figure 7 shows the trends in the intake of nutrients including carbohydrates, total protein, animal protein, and fat per capita per day from 1955 to 1990. During this period, carbohydrate intake decreased markedly, and the intake of fat and animal protein increased. Fat intake in 1990 was 56.9 g/capita/d and, therefore, still under 60 g/capita/d (2). The increase in fat and animal protein intake is attributable to increased consumption of meat, milk, and dairy products (Figure 8). Meat consumption increased dramatically until 1975, but it is still less than that of fish and

survival rate for cerebral in(26~year follow-up, Hiroshima/Nagasaki

FIGURE 6. Trends in salt consumption per capita per day in Japan, 1972 to 1990 (Japanese National Nutrition Surveys). 15

‘;i L 3

80

5

60

.$

14

70

50

13 3 $ s

12

= cz 11

________________________________________-------

10

Upper Limit of Target Salt Intake a

% 75

80

Year

85

90

Kodama STROKE TRENDS IN JAPAN

AEP Vol. 3, No. 5 September 1993: 524-528

450

527

7

400

I-

IFish

and

Shellfish,,,,-’

~~~~1~~~~~~~~~1~~

----me_____. _.._,,_.._,._

3350

Carbohydrates

..--

I-

5 f

\

30°

S? g 100 .b ii 50

0

i

Meat

I --

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FIGURE 8. Trends in food intake of meat, fish and shellfish, milk, and dairy products per capita per day in Japan, 1955 to 1990 (Japanese National Nutritional Surveys).

I

I

55

60

I

65

I

I

I

I

80

70 75 Year

85

same period, but energy intake from fat is still only 24.5%

I

and within the optimum range.

90

These life-style changes and better control of blood pressure are considered to be beneficial for stroke control and

FIGURE 7. Trends in nutrient intake of carbohydrate, protein, and fat per capita per day in Japan, 1955 to 1990 (Japanese National Nutrition Surveys).

shellfish. Milk and dairy product

consumption

steadily increasing, but the consumption 130.0 g/capita/d, countries

. ....J ... . ,..... ... .. ,.._..... /,....’

. . . . .-..-..-..-

has been

in 1990 was only

much less than in other industrialized

(2).

to be responsible for the decreased stroke incidence in Japan.

REFERENCES 1. Statistics and Information Department, Minister’s Secretariat, Ministry of Health and Welfare. Vital Statistics, 1950-90, Japan. Tokyo: Statistics and Information Department, Minister’s Secretariat, Ministry of Health and Welfare; 1950-90. (in Japanese.) 2. Nutrition Section, Ministry of Health and Welfare. National Nutrition Survey, 1955-90. Tokyo: Daiichi Shuppan Publishers; 1955-90. (in Japanese.)

COMMENTS

AND

CONCLUSION

In Japan,

stroke ranks third among

all causes of death,

following

cancer

Stroke

and heart

disease.

ranked

first

among all causes of death in Japan in 1951, and held first place for 3 decades thereafter.

Stroke mortality

tended to

increase until about 1970, but it decreased subsequently. The incidence of stroke also has been decreasing. There have been improvements

in both short- and long-term sur-

vival after stroke and case-fatality

rates have decreased in

recent years. Blood pressure levels and the prevalence of hypertension have decreased since 1965, and the nutritional

state of the

Japanese has improved. Decreased salt intake is considered to have contributed

greatly to the decreases in blood pres-

sure level and prevalence of hypertension. The mean salt intake of 14.5 g/person/d in 1972 fell to as little as 11.7 g/d in 15 years. Animal protein intake increased by 13.3% from 1960 to 1985. Fat intake increased by as much as 130% during the

3. Ueshima H, Tatara K, Asakura S, et al. Declining trends in blood pressure level and the prevalence of hypertension, and changes in related factors in Japan, 1956-1980, J Chronic Dis. 1987;40:137-47. 4. Ueshima H. Changes in dietary habits, cardiovascular risk factors and mortality in Japan, Acta Cardiol. 1990;45:31 l-27. 5. Tanaka H, Tanaka Y, Hayashi M, et al. Secular trends in mortality from cerebrovascular diseases in Japan, 1960-79, Stroke. 1982;13:57481. 6. Hasuo Y, Ueda K, Kiyohara Y, et al. Accuracy of diagnosis on death certificates for underlying causes of death in a long-term autopsy-based population study in Hisayama, Japan, with special reference to cardiovascular diseases, J Clin Epidemiol. 1989;42:577-84. 7. Shimamoto T, Komachi Y, Inada H, et al. Trends for coronary heart disease and stroke and their risk factors in Japan, Circulation. 1989; 79:503-15. 8. Lin CH, Shimizu Y, Kato H, et al. Cerebrovasculat diseases in a ftxed population of Hiroshima and Nagasaki, with special reference to relationship between type and risk factors, Stroke. 1984;15:653_^ 6U.

9. Ueda K, Omae T, Hirota Y, et al. Decreasing trend in incidence and mortality from Hisayama residents, Japan, Stroke. 1981;12:154-60. 10. Takeya Y, Popper JS, Shimizu Y, et al. Epidemiologic studies of coronary heart disease and stroke in Japanese men living in Japan, Hawaii

528

Kodama STROKE TRENDS IN JAPAN

and California: 15:15-23.

Incidence of stroke in Japan and Hawaii, Stroke. 1984;

11. Shimizu Y, Kato H, Lin CH, et al. Relationship between longitudinal changes in blood pressure and stroke incidence, Stroke. 1984;15:83946.

AEP Vol. 3, No. 5 September 1993: 524-528

12. Tanaka H, Ueda Y, Hayashi M, et al. Risk factors for cerebral hemorrhage and cerebral infarction in a Japanese rural community, Stroke. 1982;13:62-73. 13. Ueshima H, Iida M, Shimamoto T, et al. Multivariate analyses of risk factors for stroke: Eight-year follow-up study for farming villages in Akita, Japan, Prev. Med. 1980;9:722-40.