New Findings on Body Mass Index and All-Cause Mortality
Study Overview
A recent study published in The Lancet has revealed important insights regarding the relationship between body mass index (BMI) and all-cause mortality. The study underscores a correlation between high BMI and increased mortality rates, highlighting significant health risks associated with obesity. In 2015 alone, nearly four million deaths were attributed to high BMI levels.
U-Shaped Association
Major research has indicated a U-shaped association between BMI and mortality, demonstrating that both low and high BMI are linked to increased mortality rates. The lowest risk of death was observed within the healthy BMI range of 20-25 kg/m². Given the inconsistencies in findings from earlier studies, this new research sought to clarify the connection between BMI and both all-cause and cause-specific mortality.
Research Methodology
Conducted in the United Kingdom, the study utilized primary care data from the Clinical Practice Research Datalink (CPRD), which was linked to national mortality registration data. Researchers tracked the health data of participants from the commencement of the CPRD database, five years after their initial BMI record, or from January 1, 1998, until their death or March 8, 2016. The analysis included data from 3.6 million individuals, resulting in a total of 367,512 recorded deaths.
Findings on Mortality Causes
The study found that most causes of mortality, including cancer, cardiovascular diseases, and respiratory diseases, displayed a J-shaped association with BMI. This indicates a heightened risk of death at both ends of the BMI spectrum, resembling the shape of the letter “J.” The range of 21–25 kg/m² was identified as having the lowest risk of mortality.
For other causes of death, such as mental, behavioral, neurological, and non-transport-related accidental deaths, the study revealed an inverse relationship with BMI, suggesting that lower BMI figures corresponded with a higher incidence of mortality.
Demographic Insights
The associations between BMI and mortality were found to be particularly pronounced among younger populations. Additionally, individuals over the age of 40 who were classified as obese or underweight faced shorter life expectancies compared to their peers with a healthy BMI.
Conclusion
The authors concluded that BMI demonstrates a J-shaped relationship with most mortality causes, with the exception of mental and behavioral issues, where lower BMI levels are associated with greater mortality risk.
Reference
Bhaskaran, K., dos-Santos-Silva, I., Leon, D. A., Douglas, I. J., & Smeeth, L. (2018). Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3.6 million adults in the UK. The Lancet Diabetes & Endocrinology.