In a community-based cohort study published in BMC Public Health, researchers studied how anthropometric measures like the waist-calf circumference ratio (WCR), waist circumference (WC), calf circumference (CC), and body mass index (BMI) are associated with cause-specific and all-cause mortality in elderly adults.
They found that a lower CC and higher WCR are associated with an increased risk of cardiovascular disease (CVD), all-cause, and other-cause mortality.
Further, while BMI was associated with an increased risk of respiratory disease and all-cause mortality, WC could help predict cancer mortality.
Study: Association of waist-calf circumference ratio, waist circumference, calf circumference, and body mass index with all-cause and cause-specific mortality in older adults: a cohort study. Image Credit: Zdenka Darula/Shutterstock.com
Obesity and central obesity are both known to be associated with various chronic ailments. Although BMI is a common measure of obesity used to predict mortality, it does not distinguish between fat and muscle mass and fails to account for body fat distribution.
While WC is strongly linked to CVD and mortality, it may not reflect body composition accurately in older adults by itself.
On the other hand, CC, a marker of muscle mass, is reported to be associated with a lower mortality risk. Of these anthropometric measures, WCR has emerged as a promising metric of body composition that evaluates central obesity as well as muscle mass. It is a superior predictor of health outcomes than other obesity measures alone.
However, there's an absence of studies investigating the link between WCR and mortality risk in older people. This study examined the association between cause-specific and all-cause mortality and WCR among older adults.
About the study
In this study, data from 4,627 participants above 65 years of age were included from the ongoing Chinese longitudinal healthy longevity survey (2014) conducted in 22 provinces of China.
Over 52% of the participants were female, and the mean (±SD) age was 84.7 (±10.2) years. Parameters such as their WC (centimeters), CC (centimeters), height (meters), and weight (kilograms) were measured.
While WCR was calculated as the ratio of WC and CC, BMI was calculated as the ratio of weight and squared height.
As the primary outcome, all causes and specific causes of mortality were assessed, including CVD, respiratory diseases, cancer, and other causes, based on the International Statistical Classification of Diseases, 10th revision (ICD-10).
Covariates were obtained via a structured questionnaire. R-based statistical analyses included using multiple imputations by chained equations method, Cox proportional hazards models to estimate hazard ratios (HRs), 95% confidence intervals (CIs) for mortality, and Kaplan–Meier survival analysis. Sensitivity analyses were performed to validate the work.
Results and discussion
A total of 1,671 deaths occurred in the median follow-up period of 3.5 years, among which 22.9% deaths were from CVD, 5.3% from cancer, 10.4% from respiratory diseases, and 61.5% from other causes.
It was observed that WCR was higher in older, unmarried, female, and single participants, especially those who did not exercise regularly and consumed fewer vegetables in their diet. The lowest survival probabilities were found in participants with the highest quartile of WCR or the lowest quartile of CC, WC, and BMI.
Several mechanisms could potentially explain this association of high WCR with mortality, including central adiposity, leading to insulin resistance, oxidative stress, dyslipidemia, and inflammation.
All-cause, CVD, and other-cause mortality risks were higher in the third and fourth quartiles of WCR than in the second. On the contrary, the highest CC quartile was found to be associated with a decreased risk of all-cause (HR 1.42), other-cause (1.37), and CVD (HR 1.88) mortality, as compared to the second, corroborating with existing literature.
While WC showed no significant association with all-cause mortality, those participants in its first and fourth quartiles showed greater HRs for cancer mortality.
Furthermore, individuals in the first quartile of BMI and CC had a higher risk of all-cause mortality. The lowest BMI quartile showed a higher risk for all-cause and respiratory disease mortality.
Additionally, the potential association of CC with CVD and all-cause mortality was stronger in adults above 80 years compared to younger (p < 0.05). Sensitivity analyses show that the results remained consistent even when participants with preexisting conditions and missing covariate values were excluded.
Although this investigation has several strengths, including the simplicity of WCR as a measure, a prospective design, and a large sample size, further research with a longer follow-up period and assessment of temporal changes in body composition would be useful for potentially confirming these findings.
These findings suggest that WCR and CC may be better predictors for all-cause and other-cause mortality than WC and BMI in older adults.
The alarming rise in the global prevalence of obesity and its threat to public health calls for the continued identification and employment of methods for predicting mortality risk and potentially aiding therapy.