Light Pollution as a New Risk Factor for Human Breast and Prostate Cancers by Abraham Haim & Boris A. Portnov

Author:Abraham Haim & Boris A. Portnov
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

Population Level Studies

Apparently the first known attempt to test the LAN-BC association against general population data (as opposed to data for specific population groups, singled out by its professional occupation or health status, e.g., nighttime shift workers or the visually impaired), belongs to the same person who set forward the “light cycle” hypothesis—Dr. Phillip Cohen. In 1983, he and his colleagues published an empirical paper that analyzed the time of diagnosis of 3183 female patients diagnosed between 1960 and 1966 with BC in Israel (Cohen et al. 1983). A general conclusion stemming for the results of this study was that the peaks in BC detection tend to occur during spring and autumn, leading the authors to suggest that this pattern may be of hormonal nature. No link of BC incidence to LAN was hypothesized and investigated in this study though.

Eighteen years later, Davis et al. (2001) carried out a case control study of 813 cancer patients aged 20–74 years and 793 control subjects of comparable age. Personal interviews were conducted on sleep habits and the bedroom-light environment 10 years before diagnosis and lifetime occupational history. Conditional logistic regressions were used to adjust for other potential risk factors, such as family history of cancer, parity, oral-contraceptive use, and hormone-replacement therapy. The analysis revealed that BC risk was significantly higher among subjects with sleep disturbance (OR = 1.1, 95 % CI = 1.0–1.3), but no clear association between bedroom-light intensity and BC was found (OR = 1.4; 95 % CI = 0.8–2.6).

In another population-based study published by O’Leary et al. (2006), known as the “Long Island study”, the researchers investigated 576 women—residents of Nassau and Suffolk counties on Long Island, NY, who lived in the same home for more than 15 years and diagnosed with BC in 1996–1997. The BC cases were matched with 585 population-based controls. Personal interviews about LAN-exposure histories at work and home were also conducted. The questionnaire included questions about shift working, income, ethnicity, family health history and the number of sleep hours, frequency of turning lights-on during the night, and the length of time the light was on during the nighttime. According to the results of this study, BC risk was not found to be associated with either bedroom intensity bedroom light intensity (OR = 1.4; 95 % CI = 0.8–2.6) or shift work (P > 0.1). However, women who frequently turned on lights at home during sleep hours exhibited increased BC risks (OR = 1.65, 95 % CI: 1.02–2.69).

Several years later, Kloog et al. (2009a), investigated the association between bedroom light levels and BC in Israel, using a similar questionnaire such as that which was used by O’Leary et al. (2006). Kloog et al.’s study covered 1,679 women, including 794 BC diagnosed women and 885 population-based controls. The study was performed using questionnaires and self-reported LAN exposure levels—ranging from 0 (absolutely dark) to 4 (highly illuminated). Bedroom LAN was found to be significantly associated with BC risk (OR = 1.2, 1.1–1.3), controlling for education, ethnicity, fertility, and alcohol consumption.

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