Rural-urban disparities in age trajectories of depression caseness in later life: The China Health and Retirement Longitudinal Study.

BACKGROUND: No consensus has been reached on whether depression decreases or increases with age in later life. Majority of the evidence comes from Western societies, while little is known about this relationship and its rural-urban disparities in the Chinese context. METHODS: Three waves of data from 15,501 Chinese adults aged 45-85 years from the China Health and Retirement Longitudinal Study, Chinese sister study of Health and Retirement Study, were used. Depression caseness was identified using the 10-item Center for Epidemiologic Studies Depression Scale (score ≥12). Urbanisation levels were determined by combining rural-urban residence and rural-urban Hukou (a household registration system). Odds ratios and predicted probabilities of depression caseness were estimated using generalised linear mixed models. RESULTS: For both men and women and across all ages, the crude predicted probability of depression caseness was the highest in the rural group, followed by the semi-urban group, and the lowest in the urban group. The probability was stable over age among urban men (around 0.05), but it increased at an accelerated rate with age among semi-urban men (0.25 at age 85, 95% confidence interval [CI]: 0.13-0.44) and rural men (0.29 at age 85, 95% CI: 0.22-0.39). Among women the age pattern was similar between the urbanisation groups: the probability increased with age, reached a peak at ages 75-80 (urban women: 0.16, 95% CI: 0.13-0.20; semi-urban women: 0.28, 95% CI: 0.20-0.39; rural women: 0.41, 95% CI: 0.36-0.46), and decreased slightly afterwards. These differences were significantly attenuated when socio-demographic characteristics and physical disability, but not when behaviour-related factors, were controlled for. CONCLUSION: The age trajectories of later-life depression caseness varied by gender and urbanisation levels, and were not U-shaped as in many Western societies. The increasing depression caseness with age and the large rural disadvantage were substantially driven by socio-demographic characteristics and physical disability.