Association of Allostatic Load and All Cancer Risk in the SWAN Cohort

SIMPLE SUMMARY: Chronic stress has been linked to increased risks for many chronic diseases. However, its contribution to cancer risk is still unclear. In this study, we analyzed the association between allostatic load (AL), a biomarker of chronic stress, and cancer risk, in the Study of Women’s Health Across the Nation (SWAN). We found that women with the highest levels of AL had a 64% increased risk of overall cancer. And the association was independent of demographics, healthy behaviors, and socioeconomic factors. In summary, we provide evidence that chronic stress may increase the risk of cancer. ABSTRACT: Elevated chronic stress is thought to increase cancer risk, though the results so far have been inconsistent. In this study, we assessed the relationship between allostatic load (AL), a biological indicator of chronic stress, and overall cancer risk in 3015 women who participated in the Study of Women’s Health Across the Nation (SWAN). Based on the distribution of AL, the study population was categorized into four groups, from the lowest (1st category) to the highest AL group (4th category). At baseline, African American and Hispanic women were more likely to be in the higher AL categories than White women (p < 0.001). In addition, women who smoked regularly, drank alcohol regularly, had no leisure physical activity, and had restless sleep were also more likely to be in the higher AL categories than their relative counterparts (p < 0.001). We also observed that women in the lower-income category with no health insurance were more likely to be in the higher AL category (p < 0.001). The study then found that women in the 4th category of AL (the highest AL group) had a 1.64-fold increased risk of overall cancer (Hazard ratio (HR): 1.64, 95% confidence interval (CI): 1.04, 2.59). The risk association was further strengthened after adjusting demographics, healthy behaviors, and socioeconomic factors with an HR of 2.08. In further analysis of individual biomarkers of AL score, we found that higher levels of triglyceride and CRP were associated with increased risk of cancer, highlighting the role of metabolic dysfunction and inflammation in the etiology of cancer development. In summary, we report that higher AL is associated with increased cancer risk.