Association entre le risque de cancer du sein et l'exposition à la lumière artificielle la nuit

par Nirmala Prajapati

Projet de thèse en Epidémiologie

Sous la direction de Pascal Guénel.

Thèses en préparation à université Paris-Saclay , dans le cadre de École doctorale Santé Publique , en partenariat avec Centre de recherche en Epidémiologie et Santé des Populations (laboratoire) , Exposome et hérédité (equipe de recherche) et de Faculté de médecine (référent) depuis le 30-09-2021 .


  • Résumé

    Exposure to electric light, especially artificial light at night (LAN), can disrupt sleep and biological processes controlled by endogenous circadian clocks, and have adverse health consequences. The health effects of light pollution have been little studied, while almost the entire European and American population lives under a sky polluted by night light. Among the health effects potentially related to exposure to LAN, breast cancer is a priority pathology because of its high incidence in developed countries. In addition, the International Agency for Research on Cancer has classified night work as a probable carcinogen, particularly for breast cancer, on the basis of carcinogenesis mechanisms related to circadian disturbances related to exposure to artificial light. A recent meta-analysis showed that the risk of breast cancer associated with indices of high exposure to LAN was increased, but this result needs to be strongly nuanced due to the sometimes questionable methods of assessing exposure and the lack of consideration of co-exposures in the studies considered. Estimating light pollution is often based on the use of satellite data to determine the areas where the light intensity is highest, but the images used are obtained by satellites in periods of clear cloudless weather, the latter having the effect of returning light to the ground and increasing the light intensity. In addition, blue light could have specific effects on cancer risk. It therefore seems interesting to be able to use indices of the spectrum of external blue light that have been specifically developed. Studies on the health effects of exposure to LAN should also take into account night work as a source of additional exposure to LAN, consider the role of sleep disorders as mediators of the relationship between LAN and breast cancer, and consider exposure to air pollution as a confounding factor in the LAN-breast cancer relationship. The objectives of the thesis are: 1) To define geographical indicators to characterize exposure to Artificial Light during the Night (LAN) in France. 2) Investigate the association between these geographic indicators and breast cancer risk, taking into account co-factors. The project is based on data from a large case-control study on breast cancers (CECILE study) and a cohort study in women (E3N study) involving a total of more than 6000 cases of breast cancer and more than 6000 control women. The use of data from the CONSTANCES cohort is also envisaged. An approach to qualify and quantify as finely as possible light pollution on the national territory currently and retrospectively (1990-2018) will be developed from data from satellite and International Space Station (ISS) imagery, as well as data from Weather France. Statistical analyses based on multivariate models will investigate associations between indicators of environmental exposure to LAN and breast cancer. The thesis will take place under the supervision of Pascal Guénel, researcher in epidemiology, in co-supervision with Elodie Faure, geomatician engineer.

  • Titre traduit

    breast cancer, artificial light at night


  • Résumé

    Exposure to electric light, particularly artificial light at night (LAN), can disrupt sleep and biological processes controlled by endogenous circadian clocks, with adverse health consequences. The health effects of LAN have been poorly studied, while nearly all of the European and American population lives under a light polluted sky at night. Among the health effects potentially related to LAN exposure, breast cancer is of primary interest because of its high incidence in developed countries, and because the International Agency for Research on Cancer has classified night shift work as a probable carcinogen, particularly for breast cancer, on the basis of carcinogenic mechanisms linked to circadian disruption in connection with exposure to artificial light. A recent meta-analysis showed that the risk of breast cancer increased with indicators of high exposure to LAN, but this result is questionable due to unreliable methods of exposure assessment and failure to fully take into account co-exposures. The estimation of light pollution often relies on the use of satellite data to determine the areas where light intensity is strongest, but the images are only obtained in periods of clear weather, while the clouds may reflect the light towards the ground and increase the light intensity. Moreover, blue light may have a more pronounced impact on the risk of cancer. Therefore, using indices of exposure to blue light spectrum developed by some authors may be required. In addition, studies on the health effects of LAN exposure will also need to consider night work as an additional source of LAN exposure, examine the role of sleep disturbance as a mediator of the LAN-breast cancer relationship, and consider exposure to air pollutants as a potential confounder of the LAN-breast cancer relationship. The objectives of the thesis are 1) To define geographical indicators to characterize exposure to Artificial Light at Night in France. 2) To study the association between geographical indicators of LAN exposure and breast cancer risk, accounting for co-factors. The project is based on data from a large case-control study of breast cancer (CECILE study) and a cohort study of women (E3N study) involving a total of more than 6000 breast cancer cases and more than 6000 control women. The use of data from the CONSTANCES cohort is also envisaged. An approach allowing to qualify and quantify as precisely as possible the light pollution on the national territory currently and retrospectively (1990-2018) will be developed from satellite images and the International Space Station (ISS), as well as from Météo France data. Statistical analyses based on multivariate models will be used to study the associations between environmental exposure indicators to LAN and breast cancer. The thesis will be supervised by Pascal Guénel, researcher in epidemiology, in co-supervision with Elodie Faure, geomatics engineer.