Association of Aspirin Use With Mortality Risk Among Older Adult Participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

IMPORTANCE Aspirin use has been associated with reduced risk of cancer mortality, particularly of the colorectum. However, aspirin efficacy may be influenced by biological characteristics, such as obesity and age. With the increasing prevalence of obesity and conflicting data regarding the effect of aspirin in older adults, understanding the potential association of aspirin use with cancer mortality according to body mass index (BMI) and age is imperative. OBJECTIVES To investigate the association of aspirin use with risk of all-cause, any cancer, gastrointestinal (GI) cancer, and colorectal cancer (CRC) mortality among older adults and to perform an exploratory analysis of the association of aspirin use with mortality stratified by BMI. DESIGN, SETTING, PARTICIPANTS This cohort study evaluated aspirin use among participants aged 65 years and older in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial at baseline (November 8, 1993, to July 2, 2001) and follow-up (2006-2008). Analysis began in late 2018 and was completed in September 2019. MAIN OUTCOMES AND MEASURES All-cause, any cancer, GI cancer, or CRC mortality. Multivariable hazard ratios (HRs) and 95% CIs were calculated using time-varying Cox proportional hazards regression modeling, adjusting for additional factors. RESULTS A total of 146 152 individuals (mean [SD] age at baseline, 66.3 [2.4] years; 74 742 [51.1%] women; 129 446 [88.6%] non-Hispanic white) were included in analysis. The median (interquartile range) follow-up time was 12.5 (8.7-16.4) years, encompassing 1 822 164 person-years. Compared with no use, aspirin use 1 to 3 times per month was associated with reduced risk of all-cause mortality (HR, 0.84; 95% CI, 0.80-0.88; P<.001) and cancer mortality (HR, 0.87; 95% CI, 0.81-0.94; P<.001). Aspirin use 3 or more times per week was associated with decreased risk of mortality of all causes (HR, 0.81; 95% CI, 0.80-0.83; P<.001), any cancer (HR, 0.85; 95% CI, 0.81-0.88; P<.001), GI cancer (HR, 0.75; 95% CI, 0.66-0.84; P<.001), and CRC (HR, 0.71; 95% CI, 0.61-0.84; P<.001). When stratified by BMI (calculated as weight in kilograms divided by height in meters squared), aspirin use 3 or more times per week among individuals with BMI 20 to 24.9 was associated with reduced risk of all-cause mortality (HR, 0.82; 95% CI, 0.78-0.85; P<.001) and any cancer mortality (HR, 0.86; 95% CI, 0.79-0.92; P<.001). Among individuals with BMI 25 to 29.9, aspirin use 3 or more times per week was associated with reduced risk of all-cause mortality (HR, 0.82; 95% CI, 0.79-0.85; P<.001), any cancer mortality (HR, 0.86; 95% CI, 0.81-0.91; P<.001), GI cancer mortality (HR, 0.72; 95% CI, 0.60-0.86; P<.001), and CRC mortality (HR, 0.66; 95% CI, 0.51-0.85; P=.001). CONCLUSIONS AND RELEVANCE In this cohort study, aspirin use 3 or more times per week was associated with a reduction in all-cause, cancer, GI cancer and CRC mortality in older adults.