Big waist tied to higher risk of all-cause mortality

Most indices of central fatness including waist circumference, waist-to-hip ratio, waist-to-height ratio, waist-to-thigh ratio, body adiposity index, and A Body Shape Index (ABSI), independent of overall adiposity, show a positive and significant association with an increased risk of all-cause mortality, according to a study. Larger hip circumference and thigh circumference correlate with a lower risk.

“Our results suggest that measures of central adiposity could be used as a supplementary approach, in combination with body mass index, to determine the risk of premature death,” the researchers said.

Prospective cohort studies reporting the risk estimates of all-cause mortality across at least three categories of indices of central fatness were searched and identified in PubMed and Scopus from inception to July 2019, as well as in reference lists of all related articles and reviews. Those reporting continuous estimation of the associations were also included.

The researchers then performed a random effects dose-response meta-analysis to assess linear trend estimations and a one-stage linear mixed effects meta-analysis to estimate dose-response curves.

A total of 98,745 studies were screened, of which 1,950 were fully reviewed for eligibility. Seventy-two prospective cohort studies with 2,528,297 participants met the inclusion criteria. [BMJ 2020;370:m3324]

The summary hazard ratios (HRs) were 1.11 (95 percent confidence interval [CI], 1.08–1.13; I², 88 percent) for waist circumference (10 cm, 3.02-in increase; n=50), 0.90 (95 percent CI, 0.81–0.99; I², 95 percent) for hip circumference (10 cm, 3.94-in increase; n=9), 0.82 (95 percent CI, 0.75–0.89; I², 54 percent) for thigh circumference (5 cm, 1.97-in increase; n=3), 1.17 (95 percent CI, 1.00–1.33; I², 75 percent) for body adiposity index (10-percent increase; n=4), and 1.15 (95 percent CI, 1.10–1.20; I², 87 percent) for ABSI (0.005-unit increase; n=9).

For each 0.1-unit increase in waist-to-hip ratio (n=31), waist-to-height ratio (n=11), and waist-to-thigh ratio (n=2), the summary HRs were 1.20 (95 percent CI, 1.15–1.25; I², 90 percent), 1.24 (95 percent CI, 1.12–1.36; I², 94 percent), and 1.21 (95 percent CI, 1.03–1.39; I², 97 percent), respectively.

The positive associations persisted after accounting for body mass index. Waist circumference and waist-to-height ratios showed a near J-shaped association with the risk of all-cause mortality in men and women, and a positive monotonic association was seen for waist-to-hip ratio and ABSI. Finally, a U-shaped association was found for body adiposity index.

“[A]nalysis of aggregate data would have led to underestimation of relations, and several methodological approximations would have affected the analyses,” the researchers noted. “Therefore, an individual participant data meta-analysis of studies with multiple markers (including body mass index) is needed to assess the shape of these relations and their comparison or incremental value with body mass index.”

Previous studies reported the adverse effects of adiposity on systemic inflammation, oxidative stress, insulin resistance, blood pressure, lipid profile, and endothelial. [Arch Med Sci 2017;13:851-863; Int J Mol Sci 2014;16:378-400; Front Med 2013;7:14-24; Obes Rev 2018;19:654-667; Nutrients 2013;5:1218-1240; Adv Exp Med Biol 2017;960:345-379]

Earlier evidence also linked adiposity to a greater risk of cardiovascular disease, site-specific cancers, kidney disease, and neurological disorders. [Circulation 2006;113:898-918; BMJ 2017;356:j477; Stroke 2010;41:e418-26; https://jnsd.tums.ac.ir/index.php/jnsd/article/view/255]

“The number of people with overweight and obesity has doubled during the past 40 years,” the researchers said. “As a result, approximately one third of the world’s populations are overweight or obese.” [Metabolism 2019;92:6-10]