Abstract
BackgroundThe aim of this longitudinal study was to analyze whether mean Body Mass Index (BMI), assessed at four occasions, changed within different age groups and birth cohorts over time, i.e., between 1980/81 and 2004/05, after adjustment for possible confounders.MethodsA sample of 2728 men and 2770 women aged 16–71 years at study start were randomly drawn from the Swedish Total Population Register and followed from 1980/81 to 2004/05. The same sample was assessed on four occasions during the 24-year study period (i.e., every eighth year). The outcome variable, BMI, was based on self-reported height and weight. A mixed model, with random intercept and random slope, was used to estimate annual changes in BMI within the different age groups and birth cohorts.ResultsMean BMI increased from 24.1 to 25.5 for men and from 23.1 to 24.3 for women during the 24-year study period. The annual change by age group was highest in the ages of 32–39, 40–47 and 48–55 years among men, and in the ages of 24–31, 32–39, and 40–47 years among women. The highest annual changes were found in the youngest birth cohorts for both men and women, i.e., those born 1958–65, 1966–73, and 1974–81. For each birth cohort, the annual change in BMI increased compared to the previous, i.e., older, birth cohort. In addition, age-by-cohort interaction tests revealed that the increase in BMI by increasing age was higher in the younger birth cohorts (1966–1989) than in the older ones.ConclusionsPublic health policies should target those age groups and birth cohorts with the highest increases in BMI. For example, younger birth cohorts had higher annual increases in BMI than older birth cohorts, which means that younger cohorts increased their BMI more than older ones during the study period.
Highlights
The aim of this longitudinal study was to analyze whether mean Body Mass Index (BMI), assessed at four occasions, changed within different age groups and birth cohorts over time, i.e., between 1980/81 and 2004/ 05, after adjustment for possible confounders
The results show that mean BMI increased from 24.1 to 25.5 kg/m2 in men, and from 23.1 to 24.3 kg/m2 in women between
Community and health care interventions should strive to counteract the increases in BMI in the entire Swedish population, and these should target those age groups with the highest annual increases in BMI as well as younger birth cohorts, who had higher annual increases in BMI than older ones
Summary
The aim of this longitudinal study was to analyze whether mean Body Mass Index (BMI), assessed at four occasions, changed within different age groups and birth cohorts over time, i.e., between 1980/81 and 2004/ 05, after adjustment for possible confounders. Body mass index (BMI) is a useful population-level measure as it represents a simple index based on height and weight [1]. Most studies use self-reported weight and height to calculate mean BMI at the population level [5,6,7,8,9] and this is the approach that constituted the basis for the present study. Studies in many countries indicate that there have been alarming increases in mean BMI during the last few decades. It was reported that mean BMI for U.S adults (18–45 years) increased at an average rate of 2.3 kg/m2 per decade between 1986 and 2004 [5]. Increases in mean BMI have been found in other Western countries [6,7,12,13,14,15]
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