WuXi AppTec Content Team Editor
Numerous studies have linked being overweight or obese to a variety of chronic diseases and an increased risk of death. With age, it is even more difficult to maintain a healthy weight and avoid gaining weight, so people often think that “thousands of years are hard to buy old and thin.”
However, as an important indicator for measuring obesity at present, the healthy range recommendations for body mass index (BMI) are mainly based on the evidence of young and middle-aged people, and it is difficult to fully represent the elderly population. In addition, redistribution of body composition (such as fat gain, muscle loss) occurs with aging, and osteoporosis can also lead to changes in spine length, which in turn affects height… The impact of these changes on BMI also makes people Thinking, Should there be different BMI standards across the lifespan? As global aging accelerates, the answer to this question is important.
Nature-Aging recently published a 20-year prospective cohort of the Chinese population, showing that the optimal BMI range for the elderly may be those typically considered “overweight or Mild obesity” range (24.0 kg/m2~31.9 kg/m2), in this weight range, mortality was lower, mainly non-cardiovascular mortality.
Screenshot source: Nature Aging
This finding supports the ‘obesity paradox’ in older adults and challenges current guidelines for a ‘one-size-fits-all’ recommendation for adult BMI (generally considered ≥25kg/m2 Overweight, ≥30kg/m2 for obesity). The paper calls for more emphasis on providing adequate nutritional support to the elderly population to prevent underweight and weight loss.
China Centers for Disease Control and Prevention Lu Yuebin associate researcher and Shi Xiaoming researcher are the first and corresponding authors of the paper, respectively. The WuXi AppTec content team invited the paper to be interpreted by Associate Researcher Lu Yuebin.
Author’s interpretation
1. Studies have observed that “slight obesity” in the elderly is mainly associated with reduced non-cardiovascular mortality, but not cardiovascular mortality. How to understand this difference? Do fat and muscle mass contribute differently to different disease risks?
Researcher Lu Yuebin: In order to explore the reasons for this discovery, further analysis was conducted in the study, and it was found that Low fat volume would increase non-cardiovascular death Maintaining adequate muscle mass may reduce the risk of non-cardiovascular mortality. The roles of fat volume and muscle volume in the health of the elderly may not be the same. Muscle volume is very important for the maintenance of functional states such as self-care in the elderly, and is also closely related to the overall frailty of the elderly; >In addition to being a well-known cardiovascular risk factor, fat volume may also have a certain protective effect on the health of the elderly. For example, it can be used as an energy store to improve when wasting disease, surgery, trauma, etc. occur. Survival and prognosis.
2. From the perspective of the status quo of weight management in the elderly in China, what issues need attention? Nearly half of the study population were underweight at baseline. Does this mean that the phenomenon of “thinness” being unhealthy is more prominent among the Chinese elderly?
Researcher Lu Yuebin: The key health problems of the elderly in China are undernutrition rather than overnutrition, such as low body weight, anemia, nutrient deficiencies, etc. The problem of nutritional deficiencies is very prominent. In daily life, we should ensure nutritional intake, prevent the occurrence of underweight and weight loss, and pay attention to dietary diversification. Intake of protein-rich foods such as beans can improve survival and functional status in the elderly.
3. What implications do the findings have for weight and health management in older adults?
Researcher Lu Yuebin: The existing international and Chinese guidelines for overweight and obesity may not be suitable for the elderly, highage The “normal weight” of the elderly needs to be redefined; combining the results of BMI and the relationship between weight change and mortality risk, an individualized weight management strategy should be adopted for the elderly with different BMI.
Introduction to research findings
To explore optimal BMI in the elderly population, this prospective cohort study was conducted based on data from the China Elderly Health Tracking Survey (CLHLS) and included 27,026 elderly Chinese > (mean age 92.7±7.5 years), 20 years of follow-up (1998-2018), and the association of initial BMI, weight change and mortality risk was assessed.
Overall, at the start of the study, 47.1% were underweight, 42.1% were normal weight, and 8.1% and 2.7% were overweight and obese, respectively . During the follow-up period, a total of 22,165 people died, including 2,389 from cardiovascular disease and 14,681 from non-cardiovascular disease.
Statistics show a reverse J-shaped association between BMI and mortality risk: As BMI approaches the overweight and mildly obese ranges, mortality risk continues to decrease, and thereafter as BMI increases,There was no significant increase in the risk of death. The corresponding BMI values at the lowest risk points for all-cause death, cardiovascular disease (CVD) death and non-CVD death were 29.3kg/m2, 26.5kg/m2 and 30.6kg/m2, respectively.
▲Association of BMI with all-cause, CVD, and non-CVD mortality. The graph on the left is the hazard function curve, and the graph on the right is the death line and the 95% confidence interval corresponding to each BMI level. Data have been adjusted for gender, age, place of residence, educational background, occupation, source of income, marital status, lifestyle, smoking status, drinking status, exercise status, multiple disease diagnoses (heart disease, cerebrovascular disease, digestive system disease, respiratory systemic disease, hypertension, cognitive impairment, and disturbances in activities of daily living). (Image source: Reference [1])
Compared to normal weight:
Overweight and obesity and risk of non-CVD mortality (16% and 19% lower, respectively) and all-cause mortality (14% lower, respectively) % and 17%) reduced significantly, but not CVD mortality.
Underweight was significantly associated with increased mortality, with 14%, 28%, and 26% increased risk of CVD, non-CVD, and all-cause mortality, respectively.
Waist circumference, a measure of obesity, was similarly associated with risk of death.
Looking at the weight trajectory, significant weight loss is a red flag regardless of initial BMI.
A weight loss of ≥20% was associated with a 26%, 39%, and 28% increased risk of death in underweight, normal weight, and overweight/obese individuals, respectively, at study entry.
Whether weight gain is harmful depends on the initial BMI level.
Weight gain was not associated with changes in all-cause mortality in people who were underweight and normal weight at study entry.
However, weight gain is associated with increased cardiovascular mortality in pre-existing overweight/obese populations, ≥5% weight gain is associated with an increased risk of death 1.2 times.
The paper states that both sensitivity and subgroup analyses support the reliability of these results. For example, the inverse association of BMI with all-cause mortality was stronger when data on participants who died in the first 3 years of the study were excluded (considering that severe illness may itself have contributed to weight loss); In participant data, all-cause and non-CVD mortality remained the lowest in the overweight and obese population.
However, the study has certain limitations, such as only 77% of participants were identified as cause of death, and the total number of deaths resulting from CVD or non-CVD may be underestimated; second, body composition was not measured , it is difficult to explain the different effects of changes in muscle mass and body fat on health.
Image source: 123RF
In a concurrent review article in Nature-Aging, Professor Jean Woo, an international geriatrics expert and professor at the Chinese University of Hong Kong, praised this large-scale study as providing a “powerful and powerful” contribution to previous research results. support”, which is unique in that this is the oldest cohort to date and the study sample is broadly representative—covering 23 provincial-level regions in China, the number of men and women Similarly, there were similar numbers of 80-, 90-, and centenarians.
The review article further emphasizes that changes in muscle mass, fat mass, and fat distribution simultaneously constitute BMI, and that changes in muscle and fat can have important and different effects on health as we age , including multifaceted effects on chronic disease, physical and cognitive function. For older adults, maintaining muscle mass through exercise and nutrition may be more important than losing fat, Also, exercise improves cardiorespiratory fitness, which may help with higher BMI > (using general adult standards) to stay healthy.
Professional Profile
Lu Yuebin
Environmental Institute, Chinese Center for Disease Control and Prevention
Associate Investigator/Deputy Director
Main research directions:Geriatric epidemiology, environmental epidemiology