Most evidence linking body mass index (BMI) to mortality comes from measurements taken in middle or later adulthood, when illness-related weight loss can affect the results (so-called reverse causality). In this study, researchers looked at the associations between BMI at 25 years old and the overall risk of death, as well as death from specific diseases.
They used data from the China Kadoorie Biobank (CKB) study in which participants from 10 rural and urban regions of China were recruited at around 52 years of age and then followed for an average of 12 years. They used participants’ self-reported weight at 25 years old and their measured height at the start of the CKB study to calculate BMI in early adulthood.
Key findings:
- Higher BMI at age 25 (BMI25) was associated with a higher risk of death overall and from specific causes, including cardiovascular disease, cancer and respiratory disease, with risk increasing steadily with BMI25;
- People who were obese during their early adulthood (with a BMI25 of 28 kg/m2) had an 85% higher risk of premature death and death from cardiovascular disease compared with those whose BMI25 was between 18.5 and 20 kg/m²;
- Respiratory disease mortality showed a particularly strong association with early adulthood obesity and was linked to a more than doubling of risk;
- Higher BMI25 was associated with increased cancer mortality overall, but with a lower risk of breast cancer mortality among women;
- Higher BMI25 was also strongly associated with higher levels of blood glucose, but not blood pressure (after taking into account BMI in later life).
Read the full story on the Nuffield Department of Population Health website.