Baseline Cardiovascular Risk Factors and Stroke Mortality by Municipality Population Size in a 19-year Follow-up Study-NIPPON DATA80

The urban-rural difference in cardiovascular risk factors and stroke mortality throughout Japan was examined in a cohort by using hierarchical data structure. The subjects were 9,309 men and women aged ≥ 30 years who were residents of 294 areas in 211 municipalities of Japan in 1980; they were followed up until 1999. The population sizes of the municipalities in which the aforementioned areas were located were used to distinguish between urban and rural areas. We applied multilevel modeling to take into account the hierarchical data structure of individuals (subjects) (level 1) nested within areas (level 2). Statistically significant differences were observed in the case of medium (30,000-300,000) and small (<30,000) municipality populations compared with large (≥300,000) municipality populations with regard to the following parameters: body mass index in men, serum total cholesterol in both men and women, and daily alcohol drinking in women. The values or frequencies of these cardiovascular risk factors were significantly higher in large populations. Meanwhile, age-adjusted odds ratios for stroke mortality in the areas in the medium and small municipalities compared with those in the areas in the large municipalities were 1.31 (95% confidence interval (CI) 0.81-2.13) and 1.40 (95% CI 0.87-2.24) in men, and 1.32 (95% CI 0.79-2.20) and 1.62 (95% CI 0.99-2.65) in women, respectively. The results of multivariate analyses adjusted for age, body mass index, total cholesterol, diabetes, hypertension, current smoking, and daily alcohol consumption did not change materially. In conclusion, stroke mortality tended to be higher in rural areas than in urban areas in Japan, especially among women.