10-year Weight Change and Biological Aging in a Random Sample of 3,059 U.S. Adults

Telomeres play a key role in the protection of chromosomes. A good index of biological aging is the length of telomeres. Telomeres gradually shorten over time. Hence, they are strongly related to chronological age. Lifestyle is also an important factor influencing telomere length. PURPOSE: This investigation was designed to study the relationship between 10-yr weight change and leukocyte telomere length (LTL) in a large sample of 3,059 randomly selected U.S. adults, 35-70 years old. METHODS: NHANES (National Health and Nutrition Examination Survey) data were used with a cross-sectional design to determine the relationship between percent weight change and LTL. Percent weight change was calculated by subtracting baseline body weight 10-yrs earlier from current body weight and then dividing by the individual’s baseline body weight. The quantitative polymerase chain reaction method was used to measure LTL relative to standard reference DNA (T/S ratio). Covariates included age, sex, race/ethnicity, year of assessment, economic status, intent to lose weight, BMI, smoking, total physical activity, and disease status, (i.e., having or not having diabetes, cardiovascular disease, and/or cancer). Multiple regression was used to determine the linear relationship between percent weight change and LTL. Potential mediating variables were controlled using partial correlation. Because women and men differed significantly in percent 10-yr weight change and also telomere length, the data were analyzed separately by sex. RESULTS: After adjusting for age, race, year of assessment, and economic status, the association between percent 10-yr weight change and LTL was significant in women (F=8.0, P=0.0085). Controlling for all the covariates weakened the relationship slightly (F=6.5, P=0.0163). With all the covariates controlled, for each 1 percentage point increase in weight over the 10-yrs, telomeres were 3.96 base pairs (bp) shorter, on average. Given each 1-yr increase in age was associated with telomeres that were 14.2 bp shorter in women, each 3.6 percentage point increase in weight over the 10-yrs was predictive of 1 yr greater biological aging. 10-yr weight change was not associated with LTL in men. CONCLUSION: 10-yr weight change is a significant predictor of biological aging in U.S. women, but not in men

Abdominal Adiposity Indexed by the Sagittal Abdominal Diameter and Risk of Mortality in 14,119 U.S. Adults

The body mass index (BMI) is frequently used as a general measure of overweight and obesity. It is a good predictor of disease and premature death. However, research shows that indices of abdominal adiposity tend to be better predictors of disease risk and mortality than BMI. To date, the sagittal abdominal diameter (SAD), an index of abdominal adiposity, has never been evaluated as a predictor of mortality. PURPOSE: The present study was conducted to determine the extent that adults with different levels of SAD vary in their risk of all-cause mortality over an average follow-up of 6 years. METHODS: A total of 14,119 randomly selected adults, ages 20-79, from the National Health and Nutrition Examination Survey (NHANES), were included. SAD was measured by trained technicians during the years 2011-2016. The abdominal height of subjects was assessed in the supine position and a sliding-beam abdominal caliper with a built-in bubble was used to ensure a vertical measurement. Mortality data were acquired from the U.S. public-use linked mortality files (LMF), which are available for NHANES participants through 2018. Adjustments were made for 9 baseline potential confounding variables, including age, sex, race, BMI, cardiovascular disease, cancer, liver disease, smoking, and alcohol use. Subjects were divided into sex-specific quartiles based on their SAD values, and Cox proportional hazard ratios were calculated to determine risk of mortality over the follow-up period using SAS 9.4. RESULTS: With all the covariates controlled, hazard ratios showed a dose response relationship with all-cause mortality. Specifically, adults in Quartile 1 (Q1), those with the lowest sex-specific abdominal adiposity, had 0.45 (95% CI: 0.28-0.73) times the risk of mortality compared to those in Quartile 4 (Q4). Additionally, risk of mortality was 0.63 (95% CI: 0.42-0.95) for adults in Q2 vs Q4, and 0.67 (95% CI: 0.48-0.93) for Q3 vs Q4, each statistically significant. In the Q1 vs Q4 comparison, risk of mortality was 55% lower for those with the leanest SAD values. Overall, SAD was related to risk of all-cause mortality in a dose-response pattern. CONCLUSION: Epidemiologists and health care providers should seriously consider utilizing SAD as a screening tool within their programs. It is an excellent predictor of all-cause mortality