In October 16, 2019, British Medical Journal (IF=27.604) published an original research article entitled “Weight change across adulthood in relation to all cause and cause specific mortality: prospective cohort study”. This study was conducted by professor An Pan’s group from the School of Public Health, Tongji Medical College, Huazhong University of Science and Technology. This study provided novel evidence that timing of weight gain in lifecycle matters and the young adulthood to midlife transition period is an important new target for obesity prevention. The study also added to evidence about the public health importance of maintaining a normal weight across adulthood for preventing premature deaths in later life.
The harmful effect of obesity on health has been well known. However, effects of weight loss interventions were generally small and difficult to sustain and prevalence of obesity continues to increase. Previous researches mostly focused on promoting weight loss among people with overweight/obesity and obesity prevention issues in children/adolescents or in the elderly. However, young adulthood is a critical period when weight gain (mostly with body fat increase) is common. Moreover, adults gain weight more rapidly from young to middle adulthood compared with the period from middle to late adulthood when weight begins to stabilize or even decrease. Therefore, monitoring weight change since young adulthood and preventing the middle-aged spread could have a major impact on the population health. In addition, many previous studies focused on the relations of either single-time measure of body weight or weight change in middle-age and elderly populations with premature deaths, while the impacts of weight change in other life periods on mortality are not well understood. Within this context, the analysis aimed to explore the relations of long-term weight change throughout adult life with mortality, especially weight change from young adulthood to midlife.
To address the scientific question, data from 36051 participants aged 40 years and above in the US National Health and Nutrition Examination Survey who had their measured weight and height at baseline and recalled weight at age 25 years and ten years before baseline were used. Since mean age of participants was 57 (range 30-80, IQR 36-56) at baseline and 47 (range 40-90, IQR 46-66) at ten years before baseline, the period of age 25 years to ten years before baseline was approximated as the period of young adulthood to middle adulthood. Similarly, the period of age 25 years to baseline was approximated as young to late adulthood, and the ten years period before baseline was approximated as middle to late adulthood. Mortality status was followed up until December 31st 2015. Cox regression analysis based on complex survey design was used to examine the association between weight change in each period and mortality.
Results showed that stable obese was related to higher risk compared to stable normal weight, and the association was stronger for the period from young to middle adulthood (72% higher risk) compared to the period from middle to late adulthood (20% higher risk). Weight gain from young to middle adulthood was associated with increased risk of mortality from all cause and heart diseases, while the association was attenuated with increasing age. For example, compared with participants in stable normal weight group, those moving from nonobese BMI to obesity from young to middle adulthood had a 22% higher risk of all-cause mortality, while the association was attenuated to null for weigh gain pattern from middle to late adulthood. On the other hand, the association with weight loss from middle to late adulthood became stronger and significant. Therefore, the authors concluded that maintaining normal weight throughout the adulthood, especially prevention of weight gain in early adulthood, should be encouraged to reduce risk of premature deaths.
This study was funded by the National Key Research and Development Program of China to Dr. An Pan (2017YFC0907504), the China Postdoctoral Science Foundation (No. 176596) and International Postdoctoral Exchange Fellowship of the China Postdoctoral Council (No. 20180062) to Dr Xiong-fei Pan. Professor An Pan is the corresponding author, master student Chen Chen is the first author.
For more details of the paper, please visit: http://dx.doi.org/10.1136/bmj.l5584