1. The body mass index (BMI) associated with the lowest level of all-cause mortality increased by 3.3 over the past 3 decades in a cohort from Copenhagen.
2. There was a U-shaped relationship between body mass index and all-cause mortality observed in this study.
Evidence Rating Level: 2 (Good)
Study Rundown: There is a great deal of interest in determining the ideal BMI for optimal health. This study used data from the Copenhagen City Heart Study (CCHS) and the Copenhagen General Population Study (CGPS) to analyze the relationship between BMI and all-cause mortality over a 3 decade period. Three cohorts were analyzed in different years: 1976-1978, 1991-1994, and 2003-2013. In all 3 cohorts, BMI levels on each end of the scale (very-low and very-high) were associated with higher rates of all-cause mortality than more moderate BMI levels. Over time, the BMI level associated with the lowest rate of all-cause mortality increased. For example, the BMI level corresponding to the lowest level of mortality in 1976-1978 was 23.7, in 1991-1994 was 24.6, and in 2003-2013 was 27.0. Over the past 30 years, the BMI associated with the lowest all-cause mortality increased by 3.3 points.
The strengths of this study include its large sample size and its ability to follow all participants using national records. However, this study only included individuals from Copenhagen, which may limit the generalizability of its results. While this study shows that the BMI associated with the lowest all-cause mortality has increased over time, it highlights the need for further research to better understand the clinical significance of these findings.
Relevant Reading: Body-mass index and mortality among 1.46 million white adults.
In-Depth [retrospective cohort]: This study utilized data from the Copenhagen City Heart Study (CCHS) and the Copenhagen General Population Study (CGPS) to evaluate the trends in BMI associated with lowest all-cause mortality over 3 decades. The BMI associated with the lowest all-cause mortality was 23.7 (95%CI 23.4-24.3) in the 1976-1978 cohort, 24.6 (95%CI 24.0-26.3) in the 1991-1994 cohort, and 27.0 (95%CI 26.5-27.6) in the 2003-2013 cohort. There was an overall increase in BMI associated with the lowest all-cause mortality of 3.3 over the course of three decades.
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