Insulin resistance and depressive symptoms in older men: the health in men study

A positive association between depression and diabetes has been reported, but the direction and nature of this association is unclear. Insulin resistance is a state of reduced responsiveness of target tissues to normal circulating levels of insulin and predisposes to diabetes in the presence of beta cell dysfunction.

We conducted this cross-sectional and prospective study in a community representative sample of 3,140 older men free of diabetes to determine if insulin resistance was associated with prevalent and incident depressive symptoms.

Men with insulin resistance had increased odds of depression cross-sectionally (odds ratio [OR]: 1.61; 95% confidence interval [CI]: 1.08-2.40), although this was not significant after adjustment for possible confounding (OR: 1.32; 95% CI: 0.85-2.03). In the longitudinal analysis, men with insulin resistance were more likely to develop clinically significant depressive symptoms (adjusted risk ratio [RR]: 2.33; 95% CI: 1.17-4.62), and this risk was greatest for men in the highest quartile of insulin resistance compared with those in the lowest quartile (adjusted RR: 2.54; 95% CI: 1.04-6.18).

Older men with clinically significant depressive symptoms were more likely to have higher markers of insulin resistance. Additionally, the odds of depression increased with increasing levels of insulin resistance, and insulin resistance increased the risk of developing depression over 5 years later. Because depression is now a leading cause of disability worldwide, addressing the rising challenge of insulin resistance may prove important in improving the future health of our communities.