Purpose: Low serum 25(OH)D concentration has been shown to predict the occurrence of several chronic diseases. It is, however, still unclear whether the associations are causal or due to confounding. The aim of this study was to investigate the associations between serum 25(OH)D concentration and sociodemographic, lifestyle and metabolic health-related factors.
Methods: The study population comprised 5,714 men and women, aged 30-79 years, from the Health 2000 Survey representing the Finnish population. Serum 25(OH)D concentration was determined by radioimmunoassay from serum samples frozen at -70 °C. Sociodemographic, lifestyle and metabolic factors were determined by questionnaires, interviews and measurements. Linear regression was used to assess the associations between serum 25(OH)D and the factors studied.
Results: The mean serum 25(OH)D concentration was 45.3 nmol/l and it varied between categories of sociodemographic, lifestyle and metabolic health variables. Older age, being married or cohabiting and higher education were related to higher serum 25(OH)D concentration. Those with the healthiest lifestyle estimated by a lifestyle index based on body mass index, physical activity, smoking, alcohol consumption and diet had 15.8 nmol/l higher serum 25(OH)D concentration compared to those with the unhealthiest lifestyle. Of the indicators of metabolic health, only waist circumference and HDL cholesterol were significantly associated with 25(OH)D after adjustment for sociodemographic, lifestyle and other metabolic health factors.
Conclusion: This study suggests that serum 25(OH)D concentration is associated with a multitude of sociodemographic, lifestyle and metabolic health factors. Thus, it is possible that such factors confound associations observed between serum 25(OH)D concentration and chronic diseases.