Risk Factors for Stroke among Young-Old and Old-Old Community-Dwelling Adults in Japan: The Ohasama Study.

Aim: Few studies have addressed stroke risk factors in older populations, particularly among the old-old. We examined differences in traditional risk factors for stroke among the old-old compared with the young-old in community-dwelling Japanese adults. Methods: We followed 2,065 residents aged >= 60 years who had no history of stroke. Traditional risk factors for stroke were obtained from a self-administered questionnaire at baseline. We classified participants into two age categories, 60-74 years (n=1,502) and >= 75 years (n=563), and assessed whether traditional risk factors were differentially associated with stroke incidence according to age category. Hazard ratios were calculated by the Cox proportional hazards model, adjusting for confounding factors and competing risk of death. Results: During a median follow-up of 12.8 and 7.9 years, 163 and 111 participants aged 60-74 and >= 75 years, respectively, developed a first stroke. Hypertension was consistently associated with increased risk of stroke, regardless of age category. Diabetes mellitus was associated with increased risk of stroke in those aged 60-74 years (hazard ratio, 1.50; 95% confidence interval, 1.00-2.25), but not in those aged >= 75 years (hazard ratio, 0.65; 95% confidence interval, 0.33-1.29), with significant interaction by age (P=0.035). No traditional risk factor other than hypertension was associated with stroke among those aged >= 75 years. Conclusion: Those with hypertension had significantly higher stroke risk among old people, while diabetes mellitus was differentially associated with stroke according to age category. Our findings indicate the importance of different prevention strategies for stroke incidence according to age category.