Introduction: Obesity is a major risk factor for mortality from a range of causes. We investigated whether skinfold measurements predict mortality independently of variation in body mass index (BMI).
Methods: A prospective analysis of mortality in 870 apparently healthy adult Caucasian men participating in an occupational health cohort was undertaken. At baseline, skinfold measurements were taken at biceps, triceps, iliac and subscapular sites. Measurements were standardised for analysis. Derived measurements included the sum of all 4 skinfolds and subscapular to triceps, subscapular to biceps and BMI to iliac ratios. Outcomes considered included all-cause mortality and cancer, atherovascular, infection, and other deaths. Prediction of all-cause mortality was by Cox proportional hazards modelling. Competing risks analysis was used to assess predictors in specific mortality categories.
Results: There were 303 deaths during a mean of 27.7 years follow up. BMI predicted all-cause mortality and each mortality category except infection death. On multivariable analysis, with inclusion of age, BMI, smoking, alcohol and exercise, low iliac skinfold thickness independently predicted all-cause mortality (HR 0.77, 95% CI 0.66-0.90, P=0.002). Other predictors of all-cause mortality were subscapular to iliac ratio (HR 1.18, 95% CI 1.04-1.35, P=0.011), BMI to iliac ratio (HR1.25, 95%CI 1.08-1.45, P=0.002) and sum of all skinfolds (HR 0.77, 95%CI 0.65-0.92, P=0.004). Low iliac score and a high BMI to iliac ratio also predicted mortality, atherovascular and infection deaths. In multivariate analysis, low iliac emerged as the most prominent skinfold predictor of mortality. Among participants with BMI$30 kg/m2, iliac skinfold of ≤90 mm was associated with a six-fold increase in all-cause mortality risk.
Conclusion: Low iliac skinfold thickness, raised BMI to iliac ratio and raised subscapular to iliac ratio are independent risk factors for all-cause mortality in adult white males. A low iliac skinfold thickness is particularly important in obesity and its role requires further investigation.