Parent-offspring associations in metabolic syndrome and the influence of physical activity : family linkage data within the HUNT Study, Norway

Background: Cardiovascular disease is the leading cause of death worldwide. There are several factors that can increase a person's risk of developing CVD, and many of these may occur simultaneously. A clustering of risk factors for CVD can be defined as metabolic syndrome. Previous studies have shown an intergenerational association for single risk factors for CVD between parents and offspring, but few studies have examined intergenerational association of metabolic syndrome. Moreover, there is evidence that physical activity can decreased the risk of metabolic syndrome, but whether physical activity can modify an intergenerational association in metabolic syndrome is not known. Therefore, the aim of the current study is to prospectively examine the association between parental metabolic syndrome and the risk of metabolic syndrome in their adult offspring. We will also examine the independent effect of offspring physical activity, on risk of metabolic syndrome, as well as the possible modifying role physical activity may have on any intergenerational associations in metabolic syndrome. Methods: We used data on 7064 father-offspring and 9874 mother-offspring pairs from the two latest survey from the HUNT Study in Norway (HUNT2 1995-97 and HUNT3 2006-08) linked with the Family registry at Statistics Norway. Logistic regression was used to calculate odds ratio (OR) as an estimate of relative risk for metabolic syndrome in offspring, according to metabolic syndrome in their parents, as well as independent and possible modifying effects of offspring physical activity level. All associations were adjusted for offspring age, gender, smoking status and education level. Results: During the follow-up period, 2684 offspring developed metabolic syndrome. There was a positive association between parental metabolic syndrome and offspring risk of metabolic syndrome (adjusted OR=1.71 (95% CI: 1.51-1.93), if the mother had metabolic syndrome, and adjusted OR=1.50 (95% CI: 1.30-1.72), if father had metabolic syndrome). Offspring physical activity was inversely associated with risk of metabolic syndrome (adjusted OR=0.92 (95% CI: 0.81-1.03), for low level of physical activity, and adjusted OR=0.56 (95% CI: 0.47-0.67) for high level of physical activity). However, stratified analyses and tests for interaction showed no modifying effect of physical activity on the intergenerational association of metabolic syndrome. Conclusion: This study shows that there is an intergenerational association in metabolic syndrome between parents and their adult offspring. Physical activity can reduce the risk of metabolic syndrome, but do not modify the intergenerational association in risk of metabolic syndrome