Central fatness and risk of all cause mortality: systematic review and dose-response meta-analysis of 72 prospective cohort studies.

Ahmad Jayedi, Sepideh Soltani, Mahdieh Sadat Zargar, Tauseef Ahmad Khan, Sakineh Shab-Bidar

Journal: BMJ (Clinical research ed.) 2020;370():m3324

PMID: 32967840

Free Full Text on HighWire View on PubMed

Plain Language Summary

Body mass index (BMI) may not be an adequate tool to measure obesity, as it does not describe where fat is located on the body. Distribution of fat around the middle may be related to the risk of death and may be a more accurate measure of obesity. This systematic review of 1950 studies aimed to assess the association of fat around the middle with death. The results showed that every 10cm increase in waist circumference was related to an 11% increased risk of death by any cause. Women with a waist circumference greater than 80cm and 90cm in men had a higher risk of death by any cause. Fat carried around the middle increased the risk of death by any cause, however larger thigh and hip circumferences lowered the risk. This was regardless of BMI. It was concluded that measures of centrally located fat, alongside BMI, could be used to determine the risk of death. This study could be used by healthcare professionals to understand the importance of not solely relying on BMI and measuring where fat is distributed on the body may be an additional measure to determine risk of premature death.

Abstract

OBJECTIVE

To quantify the association of indices of central obesity, including waist circumference, hip circumference, thigh circumference, waist-to-hip ratio, waist-to-height ratio, waist-to-thigh ratio, body adiposity index, and A body shape index, with the risk of all cause mortality in the general population, and to clarify the shape of the dose-response relations.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed and Scopus from inception to July 2019, and the reference lists of all related articles and reviews.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Prospective cohort studies reporting the risk estimates of all cause mortality across at least three categories of indices of central fatness. Studies that reported continuous estimation of the associations were also included.

DATA SYNTHESIS

A random effects dose-response meta-analysis was conducted to assess linear trend estimations. A one stage linear mixed effects meta-analysis was used for estimating dose-response curves.

RESULTS

Of 98 745 studies screened, 1950 full texts were fully reviewed for eligibility. The final analyses consisted of 72 prospective cohort studies with 2 528 297 participants. The summary hazard ratios were as follows: waist circumference (10 cm, 3.94 inch increase): 1.11 (95% confidence interval 1.08 to 1.13, I=88%, n=50); hip circumference (10 cm, 3.94 inch increase): 0.90 (0.81 to 0.99, I=95%, n=9); thigh circumference (5 cm, 1.97 inch increase): 0.82 (0.75 to 0.89, I=54%, n=3); waist-to-hip ratio (0.1 unit increase): 1.20 (1.15 to 1.25, I=90%, n=31); waist-to-height ratio (0.1 unit increase): 1.24 (1.12 to 1.36, I=94%, n=11); waist-to-thigh ratio (0.1 unit increase): 1.21 (1.03 to 1.39, I=97%, n=2); body adiposity index (10% increase): 1.17 (1.00 to 1.33, I=75%, n=4); and A body shape index (0.005 unit increase): 1.15 (1.10 to 1.20, I=87%, n=9). Positive associations persisted after accounting for body mass index. A nearly J shaped association was found between waist circumference and waist-to-height ratio and the risk of all cause mortality in men and women. A positive monotonic association was observed for waist-to-hip ratio and A body shape index. The association was U shaped for body adiposity index.

CONCLUSIONS

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, independent of overall adiposity, were positively and significantly associated with a higher all cause mortality risk. Larger hip circumference and thigh circumference were associated with a lower risk. The results suggest that measures of central adiposity could be used with body mass index as a supplementary approach to determine the risk of premature death.

Address: Food Safety Research Center (salt), Semnan University of Medical Sciences, Semnan, Iran.; Department of Community Nutrition, School of Nutritional Science and Dietetics, Tehran University of Medical Sciences, PO Box 14155/6117, Tehran, Iran.; Department of Nutrition, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.; Nutrition and Food Security Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.; Nursing Care Research Center, Semnan University of Medical Sciences, Semnan, Iran.; Clinical Nutrition and Risk Factor Modification Centre, St Michael's Hospital, Toronto, Ontario, Canada.; Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.; Toronto 3D Knowledge Synthesis & Clinical Trials Unit, St Michael's Hospital, Toronto, Ontario, Canada.; Department of Community Nutrition, School of Nutritional Science and Dietetics, Tehran University of Medical Sciences, PO Box 14155/6117, Tehran, Iran [email protected].

DOI: 10.1136/bmj.m3324