The effect of metabolic risk factors on cancer mortality among blacks and whites

BACKGROUND: Previous data showed that metabolic syndrome (MS) and its components are associated with cancer mortality. However, whether the association varies by race is unclear. To examine the association between metabolic risk factors and cancer death in non-Hispanic whites (whites) and non-Hispanic blacks (blacks) in the US. METHODS: We used data from National Health and Nutrition Examination Survey III (NHANES III) [1988–1994], a nationwide survey conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention in the US. We included a total of 18,001 participants aged ≥20 years in the study. We ascertained cancer death from NHANES III mortality follow-up study, which linked with the National Death Index and provides follow-up from the date of baseline NHANES III [1988–1994] through December 2006. MS was defined as the presence of at least three of five risk factors [i.e., elevated triglycerides (TG) (≥150 mg/dL), impaired fasting blood glucose (≥100 mg/dL), increased waist circumference (≥88 cm for women and ≥102 cm for men), elevated blood pressure (BP) (≥130 mmHg systolic BP or ≥85 mmHg diastolic BP) and, reduced high density lipoprotein (HDL) cholesterol (<50 mg/dL)]. The interaction between race and MS and its components against total cancer mortality was first tested. Cox proportional hazards regression was then used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for total cancer mortality in relation to each MS individual component, and a MS composite score in whites and blacks, separately. RESULTS: We found a statistically significant interaction between MS and race as well as MS components and race in their effect on cancer death. In adjusted models, elevated BP was significantly associated with a 41% increased risk of total cancer death in blacks (HR 1.41; 95% CI, 1.10–1.80) while in whites, the risk of cancer death increased 29% with central obesity (HR 1.29; 95% CI, 1.05–1.59), 26% with low HDL (HR 1.26; 95% CI, 1.04–1.52), and 45% with impaired fasting glucose (HR 1.45; 95% CI, 1.19–1.76). CONCLUSIONS: The relationship between metabolic risk factors and total cancer mortality differed by race in the US. In blacks, high BP was associated with an increased risk for cancer death while in whites, central obesity, low HDL, and especially impaired fasting glucose were positively associated with cancer death.