The importance of being a “lark” in menopause

Chronotype is the attitude of a subject in determining individual circadian preference in behavioral and biological rhythm relative to the external light-dark cycle. There are three general categories: morning (MC), evening (EC) and intermediate (IC) chronotypes. MC (the so called “lark”) prefers activities earlier in the day, while EC (the so called “owl”) usually prefers to time peak activity during the late afternoon or evening and has a tendency to have more healthy problems compared to MC. IC is in an intermediate position between MC and EC. The aim of the study was to investigate the association of chronotype categories with type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD) in 80 post-menopausal women (60.7 ± 8.2 years; BMI: 31.7 ± 5.6 kg/m²; waist to hip ratio (WHR): 0.90 ± 0.07) . We assessed anthropometric parameters (BMI, WHR), adherence to the Mediterranean Diet (MD) using Predimed Score, chronotype using Morning-Evening Questionnaire and the presence of T2DM and CVD. Chronotype was classified as MC in 61% of subjects, EC in 20% and IC in 19%. No significant differences were detected in terms of BMI and WHR among the 3 categories. Subjects with EC had a significant lower adherence to MD compared to IC (4.8 ± 3.9 vs 6.7 ± 6.0; p=0.01, respectively) and MC (4.8 ± 3.9 vs 8.7 ± 8.1; p= < 0.01, respectively). Also subjects with IC had a significant lower adherence to MD assessed as PREDIMED score compared to MC (6.7 ± 6.0 vs 8.7 ± 8.1; p= < 0.01, respectively). Chronotype score was positively correlated with PREDIMED score (r=0.72; p< 0.01), i.e. the more the subjects had a tendency to wake up early and prefers activities earlier in the day the more they were adherent to the MD. Subjects with EC had a significant higher prevalence of T2DM compared to IC (38% vs 7%; p=0.03, respectively) and MC (38% vs. 10%; p= 0.01, respectively). Subjects with EC had significant higher prevalence of CVD compared to MC (56% vs 28%; p= 0.04, respectively). In conclusion although there was not difference in terms of BMI between the 3 categories, EC was associated with an increased risk of T2DM and CVD and with a low adherence to the MD in post-menopausal women. A careful assessment of the chronotype in menopause might allow tailored cardiometabolic prevention advices promoting an alignment of daily activities according their circadian rhythm in subjects with EC.