title: Twenty-five year trends in body mass index by education and income in Finland.
abstract: BACKGROUND
  The socioeconomic gradient in obesity and overweight is amply documented. However, the contribution of different socioeconomic indicators on trends of body mass index (BMI) over time is less well known. The aim of this study was to investigate the associations of education and income with (BMI) from the late 1970s to the early 2000s.
  
  
  METHODS
  Data were derived from nationwide cross-sectional health behaviour surveys carried out among Finns annually since 1978. This study comprises data from a 25-year period (1978-2002) that included 25 339 men and 25 330 women aged 25-64 years. BMI was based on self-reported weight and height. Education in years was obtained from the questionnaire and household income from the national tax register. In order to improve the comparability of the socioeconomic position measures, education and income were divided into gender-specific tertiles separately for each study year. Linear regression analysis was applied.
  
  
  RESULTS
  An increase in BMI was observed among men and women in all educational and income groups. In women, education and income were inversely associated with BMI. The magnitudes of the associations fluctuated but stayed statistically significant over time. Among the Finnish men, socioeconomic differences were more complicated. Educational differences were weaker than among the women and income differences varied according to educational level. At the turn of the century, the high income men in the lowest educational group had the highest BMI whereas the income pattern in the highest educational group was the opposite.
  
  
  CONCLUSIONS
  No overall change in the socio-economic differences of BMI was observed in Finland between 1978 and 2002. However, the trends of BMI diverged in sub-groups of the studied population: the most prominent increase in BMI took place in high income men with low education and in low income men with high education. The results encourage further research on the pathways between income, education, living conditions and the increasing BMI.
authors.affiliation: National Institute for Health and Welfare, Helsinki, Finland. ritva.prattala@thl.fi
authors.forename: Ritva
authors.initials: R
authors.lastname: Prättälä
authors.forename: Risto
authors.initials: R
authors.lastname: Sippola
authors.forename: Marjaana
authors.initials: M
authors.lastname: Lahti-Koski
authors.forename: Mikko T
authors.initials: MT
authors.lastname: Laaksonen
authors.forename: Tomi
authors.initials: T
authors.lastname: Mäkinen
authors.forename: Eva
authors.initials: E
authors.lastname: Roos
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D005387:Finland; D006801:Humans; D007182:Income / Q000706:statistics & numerical data*; D016014:Linear Models; D008297:Male; D008875:Middle Aged