Urban-rural difference in stroke mortality from a 19-year cohort study of the Japanese general population: NIPPON DATA80

In Japan, cohort studies on stroke have been mainly conducted in rural areas, with few studies comparing stroke mortality between urban and rural areas. We aimed to explore urban-rural difference in stroke mortality throughout Japan using a representative sample of the general Japanese population, the NIPPON DATA80. This study included 9309 subjects (4080 men and 5229 women) aged 30 years or older who were residents of 294 areas in 211 municipalities of Japan in 1980 and followed-up until 1999. Population size of the municipality in which the aforementioned areas were located was used to distinguish between urban and rural areas, because municipalities in Japan are classified as village, town or city principally by population size. We applied a multilevel logistic regression model to take into account the hierarchical data structure of individuals (subjects) (level 1) nested within areas (level 2), and then calculated odds ratios and 95% confidence intervals (CIs) of deaths from total stroke. Statistically significant variance between areas was not observed in men but was in women. Age-adjusted odds ratios of the areas in the medium (population > or = 30,000 and <300,000) and small municipalities (<30,000) compared with the areas in the large municipalities (> or = 300,000) were 1.31 and 1.40 in men, and 1.32 and 1.62 in women, respectively. Multivariate-adjusted odds ratios (adjusted for age, body mass index, total cholesterol, diabetes, hypertension, current smoking, and daily alcohol consumption) of the areas in the medium and small municipalities compared with the areas in the large municipalities were 1.29 and 1.36 in men, and 1.34 and 1.68 in women, respectively. In conclusion, stroke mortality tended to be higher in rural areas than in urban areas in Japan, especially among women.