Longitude Position in a Time Zone and Cancer Risk in the United States

Fangyi Gu, Shangda Xu, Susan S. Devesa, Fanni Zhang, Elizabeth B. Klerman, Barry I. Graubard, Neil E. Caporaso

Circadian disruption is a probable human carcinogen. From the eastern to western border of a timezone, social time is equal whereas solar time is progressively delayed, producing increased discrepancies between individuals' social and biological circadian time. Accordingly, western timezone residents experience greater circadian disruption and may be at an increased risk of cancer. We examine associations between the position in a timezone (PTZ) and age-standardized county-level incidence rates for total cancers combined and 23 specific cancers by gender using the data of the Surveillance, Epidemiology, and End Results Program (2000-2012), including four million cancer diagnoses in white residents of 607 counties in 11 US states. Log-linear regression was conducted, adjusting for latitude, poverty, cigarette smoking, and state. Bonferroni corrected p-values were used as the significance criteria. Risk increased from east to west within a timezone for total and many specific cancers, including chronic lymphocytic leukemia (both genders) and cancers of the stomach, liver, prostate, and non-Hodgkin lymphoma in men and cancers of the esophagus, colorectum, lung, breast, and corpus uteri in women. Risk increased from the east to the westin a timezone for total and many specific cancers, in accord with the circadian disruption hypothesis. Replication in analytic epidemiologic studies are warranted. Our findings suggest that circadian disruption may not be a rare phenomenon affecting only shift workers, but is widespread in the general population with broader implications for public health than generally appreciated.