Are Circadian Disruption and Breast Carcinogenesis Related?
Posted: Tuesday, September 15, 2020
For postmenopausal women, increased exposure to outdoor light at night may increase the risk of developing breast cancer, according to the National Institutes of Health–American Association of Retired Persons Diet and Health study published in the International Journal of Cancer. These findings “differ by individual characteristics such as smoking, alcohol drinking, sleep duration and body mass index, and neighborhood environment,” explained Rena R. Jones, PhD, MS, of the National Cancer Institute, National Institutes of Health, and colleagues.
Approximately 187,000 postmenopausal women were enrolled in the study. The cancer registry data were utilized to collect the incidence of breast cancer data for this patient population. The baseline level of exposure to light at night was determined using satellite imagery data from 1996 for all patients. Estrogen hormone receptor subtype and cancer stage were assessed for all patients.
The investigators reported that women who were in the highest quintile of baseline exposure to light at night had a significantly higher risk (10%) of developing breast cancer as compared with women in the lowest quintile of baseline exposure to light at night (hazard ratio = 1.10). Moreover, a comparison of patients with estrogen receptor–positive and estrogen receptor–negative breast cancer revealed hazard ratios of 1.12 and 1.07, respectively.
In addition, women in the lowest quintile of baseline exposure to light at night were more likely to be married (54.6%), White non-Hispanic (95.4%), and have a history of menopausal hormonal therapy (55.2%) compared with women in the highest quintile of baseline exposure to light at night (33.8% vs. 79.3% vs. 47.5%, respectively).
“Future studies should incorporate more refined [light at night] measurements at the personal level and include women from diverse racial/ethnic backgrounds and age groups,” commented the investigators.
Disclosure: For full disclosures of the study authors, visit onlinelibrary.wiley.com.