Recent Secular Trends of Body Mass Index in Individuals With Bipolar Disorders and in the General Population

Objective: The aims of this study were to investigate secular trends and distribution of body mass index (BMI) among individuals with bipolar disorders and the general population between 2008 and 2019. Methods: Data were from the Swedish National Quality Register for Bipolar Disorder, where 24,423 adults with bipolar disorders were identified, and from the national Swedish Living Conditions Surveys, where 77,485 adults from the general population were identified. Quantile regression was used to compare the 15th, 50th, and 85th percentiles of BMI across age and study years. Results: The study sample included 22,127 individuals with bipolar disorders (mean age, 48 years; 63% women) and 71,894 individuals from the general population (mean age, 52 years; 51% women). BMI percentiles were higher among individuals with bipolar disorders. At the 50th percentile, the BMI group differences were 1.1 (95% CI=0.8–1.14) for men and 1.8 (95% CI=1.5–2.1) for women. The gap was widest at the 85th BMI percentile: men, 2.3 (95% CI=1.8–2.8); women, 4.1 (95% CI=3.7–4.6). BMI increased over time in both study groups, but more in the group with bipolar disorders. The changes per decade in mean BMI were 0.4 (95% CI=0.3–0.5) among men in the general population, 1.1 (95% CI=0.7–1.4) among men with bipolar disorders, 0.6 (95% CI=0.5–0.7) among women in the general population, and 1.4 (95% CI=1.1–1.7) among women with bipolar disorders. Women with bipolar disorders had the highest prevalence and the greatest rate of increase of obesity. In 2019, the obesity prevalence was 33% among women and 29% among men with bipolar disorders, compared with 13% and 15%, respectively, among women and men in the general population. Conclusions: Adults with bipolar disorders had a higher BMI and a higher prevalence of obesity than the general population, indicating a higher cardiometabolic risk. Annually, BMI increased more in the group with bipolar disorders than in the general population, particularly among women and among those with high BMI.