Obesity and metabolic syndrome are public health problems worldwide, and present a risk to develop cardiovascular diseases. Previous findings mentioned that disruptions in the circadian clockwork may predispose to metabolic syndrome. Our aim was to find an association between seasonal changes in mood and behaviour and metabolic syndrome.

8028 participants (45% men) were interviewed face-to-face at home and assisted to a health status examination as part of a nationwide survey in Finland. Waist circumference, height, weight and blood pressure were measured and blood samples were taken for laboratory tests. They were assessed with the Seasonal Pattern Assessment Questionnaire (SPAQ) to measure seasonal changes in mood and behaviour, and the ATP-III criteria for metabolic syndrome.

Individuals with metabolic syndrome had bigger BMI (t=-42.7, df=3513, P<0.001), waist circumference (t=-47.2, df=6560, P<0,001), higher levels of glucose (t=-19.2, df=2339, P<0.001), total cholesterol (t=-13.2, df=6631, P<0.001), HDL cholesterol (t=48.5, df=5452, P<0.001), LDL cholesterol (t=-11.9, df=3800, P<0.001) and triglycerides (t=-37.5, df=2468, P<0.001). Global Seasonal Score (GSS) and seasonal changes in weight (OR=1.57, 95% CI=1.39 to 1.78) were risk factors to develop metabolic syndrome. Waist circumference correlated with seasonal symptoms, in particular with seasonal changes in weight (r=0.20, df=5986, P<0.001).

Seasonal changes were associated with metabolic syndrome. Assessment of these changes may serve as a proxy for this syndrome. Abnormalities in the circadian clockwork may predispose to seasonal changes in weight and metabolic syndrome.