Abstract
Circadian disruption (e.g. from shift work) is associated with increased risk for certain cancers. Emerging evidence suggests that sources of environmental circadian misalignment, such as solar jetlag (due to differential light exposure based on time zone position) and polycyclic aromatic hydrocarbons (PAHs; from combustion of compounds such as gasoline, damaging the transcription translation feedback loop that drives circadian rhythms at the cellular level) may impact cancer development. We examined the associations between solar jetlag, PAHs, and cancer prevalence.
We examined cancer prevalence (proportion of adults in 2022 ≥18 years diagnosed with cancer, excluding non-melanoma skin cancer) in the United States at the census tract level using Population Level Analysis and Community EStimates (PLACES). We estimated solar jetlag exposure (unitless) using a high-resolution geospatial model incorporating data on time zone position, sunrise and sunset times, and elevation. We estimated exposure to PAHs using data on smoking prevalence from PLACES; benzo[a]pyrene (BaP) and residential wood combustion from chemical transport and atmospheric dispersions models; black carbon (BC), carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter <10 microns in diameter (PM10), and PM2.5 from land-use regression; and traffic volume from averaged traffic counts. We used geographic information systems to aggregate and join these data to census tracts with areal weighting. We used Poisson regression with robust variance estimation to calculate prevalence ratios (PRs) and 95% confidence intervals (CIs) for associations between solar jetlag, PAHs, and cancer prevalence adjusting for census tract-level sociodemographics, health conditions, behaviors, socioeconomic status, and light at night.
This analysis included 77, 494 census tracts with an average cancer prevalence of 8.0%. There were no independent associations of solar jetlag or PAHs with cancer prevalence. However, there were statistically significant interactions between solar jetlag and BC, NO2, PM10, PM2.5, and traffic volume in associations with cancer prevalence. The strongest associations were observed within PM2.5 exposure strata, in which higher solar jetlag exposure was associated with increased cancer prevalence in areas with relatively higher PM2.5 levels (adjusted PR per interquartile range [45.33] increase in highest quintile of PM2.5 [8.62-35.40 µg/m3]: 1.05, 95% CI 1.04-1.07 vs. adjusted PR in lowest quintile of PM2.5 [2.05-5.89 µg/m3]:1.01, 95% CI 0.99-1.03; p interaction <0.01).
We observed interactions between solar jetlag and PAHs on cancer prevalence, suggesting that these sources of environmental circadian disruption may jointly act to impact cancer. Future research should utilize geocoded addresses, examine other sources of PAHs such as from diet, and data on cancer incidence.
Seigi Karasaki, Matthew D. Weaver, Amanda I. Phipps, Trang VoPham. Environmental circadian misalignment and cancer prevalence in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3598.
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