Risk factors for stroke in rural areas of the People's Republic of China: results of a case-control study

The Epidemiology of Stroke in the East Asian Region: A Literature-Based Review

Stroke is a leading cause of morbidity and mortality in the developed world. Our objective was to review comparable studies of stroke incidence, prevalence, and subtypes in the East Asian region. English language epidemiologic studies of stroke published from 1984 through 2004 were identified for the East Asian region (China, Hong Kong, Taiwan, Japan, North and South Korea and the ASEAN countries). The Sudlow–Warlow criteria were modified to identify comparable studies. Stroke epidemiology is relatively well characterized in China, Taiwan, and Japan; however, little information is available for other countries. Four studies of stroke incidence, from China, Taiwan, and Japan, were identified, which reported a total of 4995 first-ever stroke events. There was an over twofold difference in the age-adjusted incidence of stroke between the Chinese Seven Cities and Okinawa study (483 vs 201 per 100 000). The 1-month case fatality rate ranged from 12·7% to 17·3%. Only one population-based study on stroke prevalence, from Taiwan, was identified: Studies show the relatively high proportion of hemorrhagic stroke (30%). Stroke epidemiology is relatively well characterized in China, Japan, and Taiwan but not in other countries in the region. More recent data are needed to monitor stroke prevention efforts and guide planning of health care resources in the region.

Lifestyle factors and risk of stroke in Seoul, south Korea

BACKGROUND AND PURPOSE

The importance of stroke risk factors, especially lifestyle associated ones, may differ among different ethnic groups. The purpose of the present study is to elucidate the risk factors for stroke in Seoul, Korea.

SUBJECTS AND METHODS

Three-hundred four stroke patients and 249 age-matched controls were studied. Patients were divided into those with cerebral infarction (CI) and intracerebral hemorrhage (ICH). Using a structured interview, we assessed risk factors for stroke including lifestyle-associated factors: hypertension (HT); diabetes mellitus (DM); cigarette smoking; alcohol drinking; sodium intake; salt taste preference; physical activity and exercise; consumption of vegetables, fat, fish and fruits; body mass index; total body fat; and skinfold thickness of triceps, subscapular, and abdomen. The results were compared between patients and controls, and between CI and ICH.

RESULTS

There were 232 CI and 72 ICH. Multivariate logistic regression analyses revealed the following independent risk factors; for CI in men, HT, DM, high sodium intake, low intake of vegetables, and excessive abdominal skinfold thickness; for ICH in men, HT, heavy alcohol drinking, high sodium intake, excessive abdominal skinfold thickness, and low fat consumption; for CI in women, excessive abdominal skinfold thickness, and low fat consumption; for CI in women, HT, high sodium intake, excessive abdominal skinfold thickness, decreased triceps skinfold thickness, and lack of recent physical exercise. On subgroup comparison, DM was found to be a discriminant risk factor favoring CI (v ICH) in women.

CONCLUSION

Our results showed that in Seoul, Korea, HT is the strongest risk factor for CI and ICH, and high sodium intake, lack of exercise, and central body fat deposition are relatively important factors related to stroke, whereas factors such as cigarette smoking, hypercholesterolemia, and body mass index are not. Low consumption of fat and heavy alcohol drinking appear to be related to the occurrence of ICH. Risk factors for stroke may differ among different ethnic groups and guidelines for stroke prevention should be based on a correct understanding of them.

Subtype hypertension and risk of stroke in middle-aged and older Chinese: a 10-year follow-up study

BACKGROUND AND PURPOSE

Hypertension is the most important indicator of stroke. We aim to compare the long-term effects of the subtypes of hypertension on the risk of stroke in a Chinese cohort.

METHODS

A total of 26,587 subjects > or =35 years of age and free of stroke were recruited in 5 cities in 1987. The subtypes of hypertension were defined as isolated systolic hypertension (ISH), isolated diastolic hypertension (IDH), systolic and diastolic hypertension (SDH), as well as managed hypertension (MHT), according to the criteria of systolic blood pressure > or =140 or diastolic blood pressure >90 mm Hg or under antihypertensive treatment. The relative risks of stroke with the subtypes of hypertension, compared with normotensives, were estimated using the Cox model after adjustments for age, sex, and other confounders.

RESULTS

The prevalence of hypertension was: ISH 7.1%, SDH 18.4%, IDH 6.7%, and MHT 3.9%. During a total of 233 437 person years of follow-up, 1107 subjects developed stroke (614 ischemic and 451 hemorrhagic events and 42 unclassified). SDH patients were at the highest risk of stroke among all the hypertensives. The hazard ratio and 95% CI was 2.96 (2.49 to 3.52) for all stroke, 4.05 (3.10 to 5.30) for hemorrhagic, and 2.33 (1.84 to 2.95) for ischemic stroke. Although the incidence of stroke was higher in the older population, the effect of hypertension, especially SDH, on hemorrhagic stroke is stronger in the middle-aged population.

CONCLUSIONS

ISH and IDH are similarly prevalent in the population; both are independent predictors of stroke. Patients with SDH are at the highest risk of stroke and should be treated more aggressively.

Effects of Urban Community Intervention on 3-Year Survival and Recurrence After First-Ever Stroke

Background and Purpose— For the past 2 decades, stroke has been a principal cause of death in China, and stroke incidence tends to increase with the increase of stroke-related risk factors. The purpose of this study was to evaluate the effects of urban community-based intervention on 3-year survival and recurrence after first-ever stroke.

Methods— Two communities with a registered population of ≈50 000 each were selected as either intervention or control communities in Beijing during 1991 to 2000. Comprehensive intervention measures including the management of high-risk population and the health education of whole community population were regularly implemented. Then the influence of community intervention on 3-year survival and recurrence after initial stroke was evaluated.

Results— Within 3 years, 41.85% of 736 patients in the intervention community died whereas 40.34% of 818 patients in the control community died. Of 223 cases from the intervention community, 26 (11.66%) had a recurrent stroke within 3 years versus 52 (20.80%) of 250 cases from the control community. The statistical difference was found. Compared with the control community, the death risk of first-ever stroke in the intervention community decreased by 26% (relative risk [RR]=0.74; 95% confidence interval [CI]: 0.61 to 0.89; P =0.002); especially, that of hemorrhagic stroke decreased by 39% (RR=0.61; 95%CI: 0.46 to 0.81; P =0.001). Compared with the control community, the recurrence risk of first-ever stroke from the intervention community decreased by 42% (RR=0.58; 95% CI: 0.34 to 1.00; P =0.048).

Conclusion— Community intervention may be effective and beneficial to the recurrence prevention and survival improvement of stroke, especially hemorrhagic stroke.

Systematic Review of Methods and Results of Studies of the Genetic Epidemiology of Ischemic Stroke

BACKGROUND AND PURPOSE

To design appropriate molecular genetic studies, we first need to understand the genetic epidemiology of stroke. We therefore performed a systematic review of the literature to assess the heritability of stroke according to methodological quality of studies and to determine any heterogeneity in findings between studies and possible publication bias.

METHODS

We searched for twin studies and studies of family history of stroke using bibliographic databases and by hand-searching reference lists and journals. Odds ratios (ORs) for family history as a risk factor for stroke were calculated within studies and combined by meta-analysis. Heterogeneity between studies, methodological quality of studies, and the influence of the age at which stroke occurred in both probands and relatives were assessed.

RESULTS

We identified 53 independent studies (3 twin, 33 case-control, and 17 cohort). Monozygotic twins were more likely to be concordant than dizygotic twins (OR, 1.65; 95% CI, 1.2 to 2.3; P=0.003). A positive family history was a risk factor for stroke in both case-control (OR, 1.76; 95% CI, 1.7 to 1.9; P<0.00001) and cohort (OR, 1.30; 95% CI, 1.2 to 1.5; P<0.00001) studies. However, there was major heterogeneity between studies (cohort P=0.0001; case-control P<0.00001), with much stronger associations in small studies and methodologically less rigorous studies. Moreover, studies that reported insufficient data to allow meta-analysis tended to have found weaker associations. Family history of stroke was more frequent in studies that were confined to probands or relatives aged <70 years. However, few studies considered the number of affected and unaffected relatives, only 2 studies considered stroke phenotypes in detail, and only 19 studies (38%) adjusted associations for intermediate phenotypes. No twin study, only 5 cohort studies (26%), and 20 case-control studies (61%) differentiated between ischemic and hemorrhagic stroke in the proband. Family history of stroke was more frequent in large- and small-vessel stroke than in cardioembolic stroke. There were very few data on the influence of family history on stroke severity and no data on stroke recovery.

CONCLUSIONS

Twin studies suggest a small genetic contribution to stroke, but reliable interpretation of published family history studies is undermined by major heterogeneity, insufficient detail, and potential publication and reporting bias. More detailed large-scale genetic epidemiology is required.

Sub-optimal taurine status may promote platelet hyperaggregability in vegetarians

Although vegan diets typically have a very favorable effect on a range of vascular risk factors, several independent groups have reported that the platelets of vegetarians are more sensitive to pro-aggregatory agonists than are those of omnivores. In light of clear and convincing evidence that platelet function has an important impact on risk for thromboembolic events, it is important to clarify the basis of platelet hyperaggregability in vegetarians. A dietary deficit of long-chain omega-3 fatty acids is not likely to explain this phenomenon, since most omnivore diets do not include enough of these fats to discernibly influence platelet function. A more plausible possibility is that relatively poor taurine status--a function of the facts that plants are devoid of taurine and the human capacity for taurine synthesis is limited - is responsible. Plasma taurine levels are lower, and urinary taurine excretion is substantially lower, in vegetarians than in omnivores. Platelets are rich in taurine, which functions physiologically to dampen the calcium influx evoked by aggregating agonists--thereby down-regulating platelet aggregation. Supplemental intakes of taurine as low as 400 mg daily have been reported to markedly decrease the sensitivity of platelets to aggregating agonists ex vivo. Although the average daily intake of taurine from omnivore diets may be only about 150 mg, it is credible to speculate that a supplemental intake of this magnitude could normalize the platelet function of vegetarians in the long term; in any case, this thesis is readily testable clinically. Taurine is just one of a number of nutrients found almost solely in animal products--"carninutrients"--which are rational candidates for supplementation in vegans.

A preliminary fast may potentiate response to a subsequent low-salt, low-fat vegan diet in the management of hypertension - fasting as a strategy for breaking metabolic vicious cycles

Although a salted diet appears to be a sine qua non for the development of essential hypertension, low-salt diets often have a modest or even negligible impact on the blood pressure of hypertensives; this suggests that salt, perhaps often acting in concert with other aspects of a modern, rich diet, may set in place certain metabolic vicious cycles that sustain blood pressure elevation even when dietary salt is eliminated. Therapeutic fasting is known to lower elevated blood pressure - presumably in large part because it minimizes insulin secretion - and may have the potential to break some of these vicious cycles. Goldhamer has recently reported that a regimen comprised of a water-only fast of moderate duration, followed by a transition to a low-fat, low-salt, whole-food vegan diet, achieves dramatic reductions in the blood pressure of hypertensives, such that the large majority of patients can be restored to normotensive status, in the absence of any drug therapy. Although long-term follow-up of these subjects has been sporadic, the available data suggest that these large reductions is blood pressure can be conserved in patients who remain compliant with the follow-up diet - in other words, a 'cure' for hypertension may be feasible. If a protein-sparing modified fast can be shown to be virtually as effective as a total fast for achieving these benefits, it may be possible to implement this regimen safely on an outpatient basis. The ability of therapeutic fasts to break metabolic vicious cycles may also contribute to the efficacy of fasting in the treatment of type 2 diabetes and autoimmune disorders. As a general principle, if a metabolic disorder is susceptible to prevention - but not reversal - by a specific diet, and therapeutic fasting has a temporary favorable impact on this disorder, then a more definitive therapy may consist of a therapeutic fast, followed up by the protective diet as a maintenance regimen.

Dietary sodium, potassium, saturated fat, alcohol, and stroke mortality

BACKGROUND AND PURPOSE

Although positive relationships between blood pressure, dietary sodium, and stroke risk have been reported, studies on the relationship between dietary sodium and stroke mortality are scarce. A significant relationship between dietary saturated fatty acids (SFA) and stroke risk has not been reported in epidemiological studies. The purpose of this study was to examine the relationship between dietary sodium and SFA together with dietary potassium, alcohol, and stroke risk.

METHODS

The sex- and age-specific stroke mortality rates (log-transformed) for the age classes 45 to 54, 55 to 64, and 65 to 74 years for the period between 1986 and 1988 were obtained from World Health Organization statistics. The 24-hour urinary excretion levels of sodium (U-Na) and of potassium (U-K), dietary SFA intake levels, and alcohol consumption levels were obtained from dietary surveys performed in 17 countries. The relationships between stroke mortality and the dietary variables were examined by Pearson correlation and multiple regression analysis.

RESULTS

The highest degree of correlation, both in Pearson correlation and multiple regression analysis, was found between U-Na and log-stroke mortality (P < .01 to P < .001). In multiple regression analysis, U-Na (P < .01 to P < .001), SFA (P < .05 to P < .01), and alcohol (P < .05) independently, significantly, and positively correlated with log-stroke mortality rates, and U-K correlated negatively (P < .05). The exceptions were SFA in both sexes in the age class 45 to 54 years, alcohol in both sexes in the age class 45 to 54 years and in women in the age class 55 to 64 years, and U-K in women in the age class 65 to 74 years.

CONCLUSIONS

These results suggest that dietary factors, especially sodium and SFA, are of primary importance as determinants of stroke mortality at the population level.

Prevalence of stroke at high altitude (3380 m) in Cuzco, a town of Peru. A population-based study

BACKGROUND AND PURPOSE

We carried out a door-to-door survey on stroke prevalence at high altitude in Cuzco City, a town in the Peruvian Andes located 3380 m above sea level.

METHODS AND RESULTS

Among the 3246 screened individuals over 15 years old, there were 21 cases of first-ever completed stroke, yielding a crude prevalence ratio of 6.47 per 1000 (95% confidence interval [CI], 3.71 to 8.93 per 1000). The age-adjusted to WHO population point prevalence ratio was 5.74 per 1000 (95% CI, 3.14 to 8.35 per 1000), and the age-adjusted to North American US population point prevalence ratio was 8.58 per 1000 (95% CI, 5.44 to 11.75 per 1000). Multivariate logistic regression analysis suggested that age, polycythemia, high consumption of alcohol, and area of residence were associated with stroke prevalence. Our results suggest that the stroke prevalence in the central areas of Cuzco with sedentary people having a relatively high standard of living was higher than that in the peripheral areas with people with a relatively lower standard of living and less sedentary activities (odds ratio, 5.8; 95% CI, 1.4 to 23).

CONCLUSIONS

The prevalence of stroke suggests that stroke may be a public health problem in developing countries. This study suggests the importance of environmental factors such as altitude and lifestyle in stroke occurrence. The role of these factors should be confirmed and taken into account in future stroke prevalence studies.

Stroke incidence and mortality in rural and urban Shanghai from 1984 through 1991. Findings from a community-based registry

BACKGROUND

Mortality from stroke has declined in many countries. This decline may result from a fall in incidence of stroke or a decrease in case fatality from stroke. The present study was conducted to investigate the temporal trends of incidence rate, mortality rate, and case fatality of stroke in an urban and rural Chinese population.

METHODS

A community-based registry study was established in 1983 in defined rural and urban areas of Shanghai with a population aged 35 to 74 years of approximately 86,000 subjects, adhering to the methods and definitions of the World Health Organization MONICA protocol. All stroke events occurring in the population aged 35 to 74 years in these areas were registered by a special three-level case-registration system.

RESULTS

From 1984 through 1991, 1391 stroke cases were identified. No significant change in the incidence rate of stroke was observed from 1984 through 1991 in men and women living in rural and urban areas. Age-standardized mortality rates (per 100,000 person years) of stroke declined significantly during this period, except for rural women. The annual changes and 95% confidence intervals of age-standardized mortality rates were: for rural men -4.6% (-5.4, -3.9), for rural women -0.6% (-1.6, 0.5), for urban men -2.5% (-3.5, -1.6), and for urban women -4.7% (-5.2, -4.2). A significant decrease in case fatality from stroke from 1984 through 1991 was found among men living in rural areas (from 62.4% to 46.0%) and among women living in urban areas (from 48.4% to 33.3%). Overall case fatality, however, showed a nonsignificant decline over time.

CONCLUSIONS

We observed a decline in stroke mortality rate in a rural and urban Chinese population. No significant changes in stroke incidence were found in this study, whereas case fatality appeared to have decreased, in particular among men living in rural areas and women living in urban areas.

Incidence of stroke in Taiwan

BACKGROUND AND PURPOSE

Few epidemiological studies concerning the incidence of stroke have been conducted in Taiwan. In an attempt to investigate this common disease, we studied the incidence of stroke in Taiwan in a prospective incidence study.

METHODS

A cohort of 8,562 stroke-free people were followed up for 4 years to observe new stroke occurrence. The methods of sampling the study population have been reported elsewhere. In addition to the help of local doctors, who reported the new stroke cases, we also sent public nurses to visit the study population annually to screen the new cases of stroke.

RESULTS

There were 104 (61 men and 43 women) first-ever stroke cases identified by a neurologist in a period between October 1, 1986 and December 31, 1990. The average annual incidence rate of first-ever stroke for people aged 36 years or older in this study was 330 per 100,000. Incidence rate was higher in eastern Taiwan and in rural communities. Percentages of the major types of stroke were as follows: cerebral infarction, 71%; cerebral hemorrhage, 22%; subarachnoid hemorrhage, 1%; and unclassified, 6%. The significant risk factors for stroke were hypertension and intake of food with a high sodium content.

CONCLUSIONS

The age-specific incidence rates in this study are higher than those reported from the United Kingdom and the United States. The rates are close to those in a report from Japan and a report from a city in mainland China at the same latitude. Cerebral hemorrhages are more common among people in Taiwan than among Occidental people.