Circadian disruption is a probable human carcinogen. Dawn and dusk times occur latter in western compared to eastern regions of each time zone, producing discrepancies between individuals’ biological clock and social time which may lead to circadian disruption and increased risk of cancer. We examined associations between longitude distance from the time zone meridian and age-standardized county-specific cancer incidence rates for total and 23 specific cancers by gender. Four million whites were diagnosed with cancer during 2000-2012 in the Surveillance, Epidemiology and End Results Program in residents of 607 counties in 11 continental US states. The models were adjusted for latitude, poverty, smoking, and state as well as rural/urban location, obesity, and Hispanic composition.

The total cancer incidence rates for counties located in the western regions of time zones were significantly elevated for both men and women after Bonferroni correction. The rate ratio (RR) per five degrees of longitude toward the west (corresponding to 20 minutes delay of sunrise) was 1.03 (95% confidence intervals, CI, 1.02-1.04, p=2.7×10-6) for men and 1.04 (95% CI, 1.03-1.05, p=3.8 ×10-10) for women. Chronic lymphocytic leukemia rates for counties in the western portions of time zones were significantly elevated for both men (RR=1.13, 95% CI=1.08-1.20, p=3.1 x10-6) and women (RR=1.12, 95%CI=1.05-1.19, p=3.7 x10-4). Among men, western location within a time zone was associated with elevated risk of prostate cancer (RR=1.04, 95% CI=1.02-1.07, p=4.8 x 10-4). Among women, western location within a time zone was associated with an increase in breast cancer (RR=1.04, 95% CI=1.02-1.06, p=6.5 x 10-5) and corpus uteri cancer (RR=1.10, 95% CI=1.07-1.14, p=2.4 x 10-9 among others.

The increased cancer risk with western residency within a time zone is in accord with the circadian disruption hypothesis. Our findings suggest that circadian disruption is not a rare phenomenon affecting only shift workers or international travelers but may be widespread in the general population which has broader implications for public health than generally appreciated.

Citation Format: Neil E. Caporaso, Fangyi Gu, Shangda Xu, Susan S. Devesa, Fanni Zhang, Elizabeth B. Klerman, Barry Graubard. Circadian disruption and cancer risk in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 272. doi:10.1158/1538-7445.AM2017-272