Author information
1
Epidemiology, Harvard T.H. Chan School of Public Health tvopham@hsph.harvard.edu.
2
Division of Sleep and Circadian Disorders, Brigham and Women's Hospital.
3
Department of Integrative Physiology, University of Colorado Boulder.
4
Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School.
5
Channing Division of Network Medicine, Brigham and Women's Hospital.
6
Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School.
7
Slone Epidemiology Center, Boston University.
Abstract
BACKGROUND:
Circadian misalignment may increase the risk of developing hepatocellular carcinoma (HCC). The aim of this study was to examine the association between distance from time zone meridian, a proxy for circadian misalignment, and HCC risk in the U.S. adjusting for known HCC risk factors.
METHODS:
Surveillance, Epidemiology, and End Results (SEER) provided information on 56,347 HCC cases diagnosed between 2000 and 2014 from 16 population-based cancer registries in the U.S. Distance from time zone meridian was estimated using the location of each SEER county's Center of Population in a geographic information system (GIS). Poisson regression with robust variance estimation was used to calculate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for the association between distance from time zone meridian and HCC risk adjusting for individual-level age at diagnosis, sex, race/ethnicity, year of diagnosis, SEER registry, and county-level prevalence of health conditions, lifestyle factors, shift work occupation, socioeconomic status, and demographic and environmental factors.
RESULTS:
A 5 degree increase in longitude moving east to west within a time zone was associated with a statistically significant increased risk for HCC (IRR 1.07, 95% CI 1.01-1.14, p = 0.03). A statistically significant positive association was observed among those <65 years old, while no association was observed among individuals ≥65 years old (p for interaction < 0.01).
CONCLUSIONS:
Circadian misalignment from residing in the western region of a time zone may impact hepatocarcinogenesis.
IMPACT:
Circadian misalignment may be an independent risk factor for HCC.