Economic disadvantage is related to a higher risk of adulthood obesity, but few studies have considered whether changes in economic circumstances depend on a person's body mass index (BMI) trajectory. We identified latent BMI trajectories among midlife and ageing Finns and captured individual-level changes in economic circumstances within the BMI trajectories utilizing sequence analysis. We used the Helsinki Health Study cohort data of initially 40-60-year-old Finnish municipal employees, with four survey questionnaire phases (2000-2017). Each survey included identical questions on height and weight, and on economic circumstances incorporating household income and current economic difficulties. Based on computed BMI, we identified participants' (n = 7105; 82% women) BMI trajectories over the follow-up using group-based trajectory modeling. Four BMI trajectories were identified: stable healthy weight (34% of the participants), stable overweight (42%), overweight to class I obesity (20%), and stable class II obesity (5%). Lower household income level and having economic difficulties became more common and persistent when moving from lower- to higher-level BMI trajectories. Differences in household income widened over the follow-up between the trajectory groups, whereas economic difficulties decreased equally in all trajectory groups over time. Our study provides novel information on the dynamic interplay between long-term BMI changes and economic circumstances.
Keywords: body mass index; economic difficulties; household income; obesity; sequence analysis; trajectory modeling; weight gain.