Association between pet ownership and the risk of dying from colorectal cancer: an 18-year follow-up of a national cohort

Background Despite the popularity of pets, research on the relationship between pet ownership and the risk of cancer remains minimal and inconclusive. Aim To longitudinally examine the association between pet ownership and the risk of dying from colorectal cancer. Methods We analyzed the data of a nationally representative cohort of 13,929 adults aged >= 19 years who answered the question about pet ownership in the Third National Health and Nutrition Examination Survey (NHANES), 1988-1994. The vital status was followed through 31 December 2010. Results Approximately, 43% of the participants had pets, 26% with dogs, 20% with cats and 5% with birds. By the end of an 18-year follow-up (mean = 15 years), 70 colorectal cancer deaths were recorded. After adjustment for socio-demographic factors, cigarette smoking, alcohol drinking, body mass index, physical activity, history of atopic conditions and serum cotinine measured at the baseline survey, the hazard ratio (HR) of dying from colorectal cancer associated with having any pets was 2.83 (95% CI = 1.51-5.30) compared with non-pet owners. This association was largely attributed to owning a cat. The HR of dying from colorectal cancer for owning a cat was 2.67 (1.22-5.86). The HR for owning a dog was 0.89 (0.37-2.12). Conclusions Having a cat was significantly associated with an elevated risk of dying from colorectal cancer among the general population. The observed detrimental effects the cats conferred may not be explained by confounding effects from socio-demographics, cigarette smoking, sedentary life or atopic conditions.