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

A black-white disparity in total cancer death has been pervasive in the US, despite the general decline in cancer mortality rates due to reduced tobacco smoking, more widespread cancer screening and testing, and improved therapies (1). The reasons for black-white differences in cancer outcomes and survivorship are multifactorial. Factors from individual (2,3), clinical (4,5) and environmental (6-8) levels contribute to this disparity but were not able to provide a complete explanation. Previous studies found racial differences in cancer outcomes remain even after adjusting for stage, age, sex, socioeconomic status and access to health care (9-12). One factor that might contribute to the racial differences in cancer death but that has not fully evaluated is metabolic syndrome (MS). MS is defined as a cluster of at least three of the following risk factors: central obesity, glucose intolerance, dyslipidemia and hypertension (13). There is a growing interest in MS because of its high prevalence among US adults (14) and its link with risk of many chronic conditions including various cancers (15-18). MS and its individual components may be also related to increased cancer mortality (19-22). One perspective study found MS was associated with an increased risk of all-cause cancer mortality in men (20). Another population-based study in the US also reported a significant association between MS and total and lung cancer mortality. Specifically, systolic blood pressure (BP) and serum glucose were positively associated with an increased risk of death from total cancer (19). However, these studies exploring MS and cancer outcomes often aggregated racial groups, thereby masking possible differences in association by race (19-22)