Factors associated with depression across age groups of older adults: The Singapore Chinese health study.

Objectives: We studied sociodemographic and health factors associated with depression across three age groups of community-dwelling older adults.

Methods/design: We used data from 16,785 participants from the third follow-up of the Singapore Chinese Health Study (mean age: 73, range: 61-96 years). We defined depression as having a score of ≥5 using the 15-item Geriatric Depression Scale. We used regression splines to examine the pattern of depression risk with age and applied multivariable logistic regression to study factors associated with depression.

Results: Increasing age was associated with depression in an inverted J-shape relationship with the highest odds ratio (OR) at age 75. Compared to the youngest-old (<70 years), the middle-old (70-80 years) had higher odds of depression [OR = 1.20, 95% confidence interval (CI) = 1.09-1.31], while the oldest-old (>80 years) had no increased risk (OR = 1.01, 95% CI = 0.89-1.15). We also found demographic (men, lower education, unemployment), social (living alone, poor social support, no social activity) and health factors (instrumental limitations, poor physical function, function-limiting pain, chronic diseases, cognitive impairment, poor sleep quality, poor self-rated health) associated with depression. In stratified analysis by age groups, the OR estimates for lower education level, instrumental limitations and cognitive impairment decreased with age, whereas the risk of depression for men increased with age (all p-values for interaction<0.03).

Conclusions: Compared to the youngest-old, the likelihood of depression was highest among middle-old adults and decreased to null in the oldest-old. The associations between some factors and depression were attenuated with age, suggesting a coping mechanism among oldest-old survivors.