Combined lifestyle factors and metabolic syndrome risk: a systematic review and meta-analysis

Background/Objectives: The metabolic syndrome is a complex condition influenced by many factors including lifestyle. Recently, more and more studies explored the relationships between combined lifestyle factors (often measured as lifestyle scores/indices) and metabolic syndrome due to the co-occurrence of these factors. These scores/indices considered potential interactions among lifestyle factors, offering a more comprehensive understanding of their relationship with metabolic syndrome. However, no review/meta-analysis has been conducted to summarize existing evidence. Thus, this study aimed to synthesize the associations between lifestyle scores/indices and metabolic syndrome in cross-sectional and cohort studies. Subjects/Methods: A literature search was performed in Embase and Medline. Multivariable-adjusted estimates were synthesized using random-effects models. In research where higher scores indicated better health, we used original estimates directly. In studies where higher scores denoted poorer health, we first calculated the coefficients and standard errors based on original estimates. Afterward, we reversed coefficients’ directions and recalculated new estimates. Thus, the pooled estimates compared the healthiest with the least-healthy lifestyles (the highest vs. lowest scores/indices). Subgroup analyses were conducted based on study design, region, baseline time, baseline age, sex, health status, metabolic syndrome diagnosis, and lifestyles’ number. Sensitivity analyses were performed by including only high-quality studies and employing leave-one-out analyses. Results: Nineteen studies from 16 publications were included. Physical activity, diet, and smoking were the top three included lifestyle factors. Compared to participants with the least-healthy lifestyles, those with the healthiest lifestyles had a 43% lower metabolic syndrome risk (95% confidence interval = 0.41–0.73). In subgroup analyses, healthy lifestyle scores/indices were inversely associated with both metabolic syndrome prevalence in cross-sectional studies (Odds ratio = 0.62; 95% confidence interval = 0.51–0.73) and metabolic syndrome incidence in cohort studies (Odds ratio = 0.40; 95% confidence interval = 0.11–0.68). The inverse association was consistent in other subgroup and sensitivity analyses. Conclusions: Adherence to a healthy lifestyle pattern was beneficial to metabolic syndrome prevention.