Chronotype and metabolic syndrome in midlife: findings from the Northern Finland Birth Cohort 1966.
Level 4 - case-series / case-control
Cross-sectional analysis within a prospective birth cohort
PubMed 38758129 · doi:10.1152/ajpheart.00051.2024
What was done
Researchers evaluated the cross-sectional association between chronotype and metabolic syndrome using data from the Northern Finland Birth Cohort 1966 (NFBC1966) at age 46 (n = 5,113; 57% female). Chronotype was assessed via a shortened Morningness-Eveningness Questionnaire (morning 44%, intermediate 44%, evening 12%). Metabolic syndrome was defined according to International Diabetes Federation criteria. Logistic regression analyses were adjusted for alcohol consumption, smoking, marital status, education level, and leisure-time physical activity.
What was found
In women, the prevalence of metabolic syndrome was significantly higher among those with an evening chronotype (34%) compared to morning (23%) and intermediate (24%) types (P < 0.001). After multivariable adjustment, evening chronotype in women was associated with an increased risk of metabolic syndrome (odds ratio 1.5, 95% CI 1.2 to 2.0). No statistically significant association between chronotype and metabolic syndrome was observed in men.
Why it matters
These findings suggest that evening chronotype is an independent risk marker for midlife metabolic syndrome specifically in women, supporting sex-specific pathways in circadian-metabolic health.
Limits
The analysis evaluated chronotype and metabolic syndrome cross-sectionally at age 46, precluding causal inference. Chronotype was determined via a shortened self-report questionnaire rather than objective circadian markers (e.g., dim-light melatonin onset or actigraphy). The cohort is geographically and ethnically homogeneous to Northern Finland.
Cited by
- supports Intermediate chronotypes (bears) make up between 50% and 55% of the population.