Combined Influence of Waist and Hip Circumference on Risk of Death in a Large Cohort of European and Australian Adults

Abstract

Background Waist circumference and hip circumference are both strongly associated with risk of death; however, their joint association has rarely been investigated. Methods and Results The MONICA Risk, Genetics, Archiving, and Monograph (MORGAM) Project was conducted in 30 cohorts from 11 countries; 90 487 men and women, aged 30 to 74 years, predominantly white, with no history of cardiovascular disease, were recruited in 1986 to 2010 and followed up for up to 24 years. Hazard ratios were estimated using sex-specific Cox models, stratified by cohort, with age as the time scale. Models included baseline categorical obesity measures, age, total and high-density lipoprotein cholesterol, systolic blood pressure, antihypertensive drugs, smoking, and diabetes mellitus. A total of 9105 all-cause deaths were recorded during a median follow-up of 10 years. Hazard ratios for all-cause death presented J- or U-shaped associations with most obesity measures. With waist and hip circumference included in the same model, for all hip sizes, having a smaller waist was strongly associated with lower risk of death, except for men with the smallest hips. In addition, among those with smaller waists, hip size was strongly negatively associated with risk of death, with ≈20% more people identified as being at increased risk compared with waist circumference alone. Conclusions A more complex relationship between hip circumference, waist circumference, and risk of death is revealed when both measures are considered simultaneously. This is particularly true for individuals with smaller waists, where having larger hips was protective. Considering both waist and hip circumference in the clinical setting could help to best identify those at increased risk of death.

Keywords: hip circumference; mortality; obesity; waist circumference.

Figure 1. Risk of death, according to obesity measures, by sex and cause of death, estimated after adjustment for cardiovascular risk factors.

Hazard ratios for all‐cause (A and B) and cardiovascular (C and D) death by sex, with 95% CIs, are shown for each obesity measure: body mass index (BMI; weight in kilograms divided by the square of the height in meters), weight/hip ratio (WHR), a body shape index (ABSI; waist circumference in meters/[BMI^2/3×height in meters^½]), weight/height ratio (WHtR), waist circumference, and hip circumference. Vertical lines indicate 95% CIs. Reference category for each obesity measure was ≥−0.5 SDs to ≤0.5 SDs from the sample sex‐specific mean. Risks were estimated from Cox proportional hazards models, stratified by cohort, and adjusted for age at baseline, log of total cholesterol (mmol/L), log of high‐density lipoprotein (HDL) cholesterol (mmol/L), systolic blood pressure (mm Hg), taking antihypertensive drugs, current daily smoker (cigarettes, cigars/cigarillos, or pipe), diabetes mellitus, and all interactions between age and baseline measures that were statistically significant (P<0.001). ^†Additionally adjusted for an interaction between age at baseline and log of HDL cholesterol (mmol/L). ^#Additionally adjusted for interaction between age at baseline and systolic blood pressure. ^&Additionally adjusted for interaction between age at baseline and current daily smoker.

Figure 2. Risk of death, according to waist circumference within hip circumference levels, by sex and cause of death, estimated after adjustment for cardiovascular risk factors.

Hazard ratios for all‐cause (A and B) and cardiovascular (C and D) death by sex, with 95% CIs, are shown for all feasible combinations of waist circumference and hip circumference. Vertical lines indicate 95% CIs. Reference category was ≥−0.5 SDs to ≤0.5 SDs from the sample sex‐specific mean for both waist circumference and hip circumference. Risks were estimated from Cox proportional hazards models, stratified by cohort, and adjusted for age at baseline, log of total cholesterol (mmol/L), log of high‐density lipoprotein (HDL) cholesterol (mmol/L), systolic blood pressure (mm Hg), taking antihypertensive drugs, current daily smoker (cigarettes, cigars/cigarillos, or pipe), diabetes mellitus, and all interactions between age and baseline measures that were statistically significant (P<0.001). ^†Additionally adjusted for an interaction between age at baseline and log of HDL cholesterol (mmol/L). ^#Additionally adjusted for an interaction between age at baseline and systolic blood pressure. ^&Additionally adjusted for an interaction between age at baseline and current daily smoker.

Figure 3. Risk of death, according to hip circumference within waist circumference levels, by sex and cause of death, estimated after adjustment for cardiovascular risk factors.

Hazard ratios for all‐cause (A and B) and cardiovascular (C and D) death by sex, with 95% CIs, are shown for all feasible combinations of waist circumference and hip circumference. Vertical lines indicate 95% CIs. Reference category was ≥−0.5 SDs to ≤0.5 SDs from the sample sex‐specific mean for both waist circumference and hip circumference. Risks were estimated from Cox proportional hazards models, stratified by cohort, and adjusted for age at baseline, log of total cholesterol (mmol/L), log of high‐density lipoprotein (HDL) cholesterol (mmol/L), systolic blood pressure (mm Hg), taking antihypertensive drugs, current daily smoker (cigarettes, cigars/cigarillos, or pipe), diabetes mellitus, and all interactions between age and baseline measures that were statistically significant (P<0.001). ^†Additionally adjusted for an interaction between age at baseline and log of HDL cholesterol (mmol/L). ^#Additionally adjusted for an interaction between age at baseline and systolic blood pressure. ^&Additionally adjusted for an interaction between age at baseline and current daily smoker.