Data were from 851 participants (65-94 years) of the InCHIANTI Study and 1064 (26-93 years) of the Baltimore Longitudinal Study of Aging (BLSA). Plasma concentrations of leptin, waist circumference and depressive symptoms via the Center for Epidemiological Studies-Depression scale (CES-D) were assessed. In longitudinal InCHIANTI analyses onset of depressed mood (CES-D鈮?0) was evaluated over a 9-year follow-up.
In pooled cross-sectional analyses the interaction between leptin and waist circumference was significantly associated with CES-D scores ((log)leptin-by-waist interaction p = 0.01). Also in longitudinal analyses, the (log)leptin-by-waist interaction term significantly (p = 0.04) predicted depressed mood onset over time; depressed mood risk was especially increased for high levels of both leptin and waist circumference.
The present findings suggest that low leptin signaling rather than low leptin concentration is a risk factor for depression. Future studies should develop proxy measures of leptin signaling by combining information on abdominal adiposity and leptin level to be used for clinical and research applications.