"Among well-functioning older adults, DM [Diabetes Mellitus] is associated with increased risk of depressive symptoms."Those whose diabetes was poorly controlled (whose HbA1c was > 7%) were particularly at risk.
It was a prospective study with a mean follow-up of 5.9 years. The 2522 participants, aged 70 to 79, were community-dwelling and did not have depression at the beginning of the study. (Although it was not known if depression existed prior to study entry.)
The causal mechanisms of a diabetes-depression association have not been unraveled. That is, we still don't know if one is primarily at the root of the other. This study however demonstrated that having diabetes can almost double the risk for depression (even after, as in this case, adjustments are made for age, sex, race, education, smoking, alcohol intake, activity level, and baseline depression score).
Although this study observed that "depressive symptoms may be in part explained by the global burden of comorbidities and impairments associated with DM," they pointed out that other organic causes may be contributing, particularly those related to HbA1c levels.
This is one more data point in the diabetes-depression narrative.
For the abstract:
Diabetes Mellitus, Glycemic Control, and Incident Depressive Symptoms Among 70- to 79-Year-Old Persons