Intergenerational social mobility and body mass index trajectories - A follow-up study from Finland.

J Salmela,T Lallukka,N Kanerva,E Mauramo,O Pietiläinen,O Rahkonen

doi:10.1016/j.ssmph.2020.100723

Abstract

Evidence remains unclear on how intergenerational social mobility is associated with body mass index (BMI) and its long-term changes. Our study identified BMI trajectories from middle to older age by intergenerational social mobility groups and stratified the analyses by gender and two birth cohorts (birth years 1940‒1947 and 1950–1962). We used questionnaire-based cohort data that consists of four survey phases: 2000–2002, 2007, 2012, and 2017. In Phase 1, participants were 40–60-year-old employees of the City of Helsinki, Finland. Our analytical sample consisted of 6,971 women and 1,752 men. Intergenerational social mobility was constructed based on self-reported parental and own education—both divided into high and low—yielding four groups: stable high socioeconomic position (SEP) (high-high), upward social mobility (low-high), downward social mobility (high-low), and stable low SEP (low-low). BMI was calculated from self-reported height and weight from all four phases. Using mixed-effects linear regression, we found increasing BMI trajectories in all four social mobility groups until the age of 65. Women and men with stable high SEP had lower BMI trajectories compared to those with stable low SEP. In the younger birth cohort, women with upward social mobility had a lower BMI trajectory than women with stable low SEP. Additionally, women and men with downward social mobility had higher BMI trajectories than those with stable high SEP. In the older birth cohort, however, the BMI trajectories of upward and downward social mobility groups were somewhat similar and settled between the BMI trajectories of stable high and stable low SEP groups. Our results indicate that the associations between intergenerational social mobility and BMI may depend on gender and birth cohort. Nevertheless, to reduce socioeconomic inequalities in unhealthy weight gain, obesity prevention actions that focus on people who are likely to remain in low SEP might be worthwhile.

Highlights

Unhealthy weight gain remains a great challenge for public health
Among women with stable high socioeconomic position (SEP) and upward social mobility, higher household income, less economic difficulties, being a non-smoker, and better physical health functioning were more common compared to women with downward social mobility and stable low SEP (Table 1)
A similar distribution could be seen among men, as well as being married or co-habiting, daily fruit and vegetable consumption, and being vigorously active in leisure-time were more common among stable high SEP and upward social mobility groups than among down ward social mobility and stable low SEP groups (Table 2)

Summary

Introduction

Overweight and obesity increase the risk of morbidity and mortality (Nyberg et al, 2018; The Global BMI Mortality Collaboration, 2016), and a growing number of people worldwide are exposed to that burden (NCD Risk Factor Collaboration (NCD-RisC), 2017). Low socioeconomic position (SEP) is a known risk factor for obesity. Both low parental (Senese et al, 2009; Strand et al, 2012) and an individual’s own SEP That has led researchers to investigate different life-course models to describe the associations between life-course SEP and BMI. Less attention has been paid to examining whether intergen erational social mobility—that is, the movement from parental SEP to one’s own SEP—affects BMI and its long-term changes. We focus on the associations between intergenerational social mobility and BMI trajectories in the Finnish context

Methods

Results

Discussion

Conclusion