Season of birth and dementia: Findings from Chinese elderly based on a nationwide data.

Abstract

Previous studies showed inconsistent results regarding the association between season of birth and dementia later in life. Evidence has mainly come from developed countries with relatively homogeneous geographical features. In this study, we examined the association between season of birth and dementia among Chinese elderly as well as geographical region-specific and urban/rural-specific patterns. We utilized data from the Second China National Sample Survey on Disability in 2006, and employed multivariate logistic regression to estimate the association between dementia and birth seasonality. We conducted subsample analyses by urbanity and geographical region. This study included 354 859 Chinese elderly aged 60 and above. Compared with the summer-born, the odds of dementia were significantly lower among those born in winter (OR: 0.82, 95% CI: 0.70, 0.96). Similar associations were also found in urban and northern subsamples. Winter birth was associated with a lower prevalence of dementia in old age, especially among those living in urban and northern areas of China. This association further suggests the critical role of early life period and environment on health in later life.