Both diabetes and depression have become serious public health problems and are major contributors to the global burden of disease. People with diabetes have been shown to have higher risk of depression. The purpose of this study was to observe the differences in depression between older Chinese adults with known or unknown diabetes.

Data came from the national baseline survey of China Health and Retirement Longitudinal Study (CHARLS). The Center for Epidemiologic Studies Depression Scale was used to assess depression. Participants with a history of diabetes diagnosis were considered to have known diabetes, and those with newly-diagnosed diabetes were considered to have unknown diabetes. Multiple logistic regression analysis was applied to estimate odds ratio (OR) for depression in predictor variables.

Overall, 39.1% of the 2,399 participants with diabetes suffered from depression. The prevalence of depression was significantly higher (p < 0.001) in people with known diabetes (43.5%) than those with unknown diabetes (35.1%). The biggest differences between the two groups were found in the middle aged, in women, in the less educated and in married people. In known diabetes, people treated with traditional Chinese medicine (TCM) coupled with oral western medicine (WM) and/or insulin had two-fold odds of depression compared to those without treatment.

The knowledge of having diabetes, treatments and suffering from other chronic diseases were associated with the higher prevalence of depression in people with known diabetes compared to those with unknown diabetes. Prevention of depression in diabetics should receive more attention in the middle aged, women and the less education.