Associations between Childhood Disadvantage and Adult Body Mass Index Trajectories: A Follow-Up Study among Midlife Finnish Municipal Employees

Objective: Childhood disadvantage is associated with a higher risk of adult obesity, but little is known about its associations with body mass index (BMI) trajectories during adulthood. This study aimed first to identify adulthood BMI trajectories, and second to investigate how childhood disadvantage is associated with trajectory group membership. Methods: Data from the Helsinki Health Study, a longitudinal cohort study of initially 40- to 60-year-old employees of the City of Helsinki in Finland, were used. The baseline survey was conducted in 2000-2002, and similar follow-up surveys in 2007, 2012, and 2017. Based on self-reported BMI, participants' (n =5,266; 83% women) BMI trajectories, including their retrospectively reported BMI at the age of 25 years, were examined. Data on childhood disadvantage, including parental education and 7 types of childhood adversity (their own serious illness; parental divorce, death, mental disorder, or alcohol problems; economic difficulties at home; and peer group bullying) before the age of 16 years, were obtained from the baseline survey. Group-based trajectory modeling was used to identify BMI trajectories, and multinomial logistic regression to analyze the odds for trajectory group membership for the disadvantage variables. Results: Four ascending BMI trajectories in women and men were found: persistent normal weight (trajectory 1; women 35% and men 25%), normal weight to overweight (trajectory 2; women 41% and men 48%), normal weight to class I obesity (trajectory 3; women 19% and men 23%) and overweight to class II obesity (trajectory 4; women 5% and men 4%). Compared to trajectory 1, women with multiple adversities and repetitive peer bullying in childhood had greater odds of belonging to trajectories 3 and 4, whereas men with parental alcohol problems had greater odds of belonging to trajectory 4. For women and men, a low level of parental education was associated with a higher-level BMI trajectory. Conclusions: Low parental education for both genders, multiple adversities and repetitive peer bullying in childhood among women, and parental alcohol problems among men increased the odds of developing obesity during adulthood. Further studies are needed to clarify how gender differences modify the effects of childhood disadvantage on adult BMI trajectories.