There is little data as to whether exposure to residential greenness is associated with the incidence of breast cancer. Lack of physical activity and obesity are two of the accepted risk factors for postmenopausal breast cancer and living near green areas may contribute to an active lifestyle and maintaining a normal body mass index and, consequently, residential greenness may be associated with lower incidence rates.
The objective of this study was to determine whether there was an association between past exposure to residential greenness and the incidence of invasive postmenopausal breast cancer among Canadian women living in Montreal, Quebec, in the mid-2000s.
We conducted a population-based, case-control study of incident postmenopausal breast cancer in Montreal, Canada, and herein we show analyses by level of greenness surrounding participants’ homes. Incident cases were identified between 2008 and 2011 from all but one hospital that treated breast cancer in the Montreal area. Population controls were identified from provincial electoral lists of Montreal residents and frequency-matched to cases on age. Residential greenness was estimated using the maximum daily normalized difference vegetation index averaged over the growing season (“maximum NDVI”). Maximum NDVI was assigned at the home address of recruitment for the years 1992–1998 (about 15 years before diagnosis), and we measured subjects’ personal information, exposure to NO 2 and ultrafine particles, and area-wide variables to control for potential confounding effects. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer associated with residential greenness were estimated using logistic regression models adjusting for various combinations of potential confounders. We assessed the functional form of maximum NDVI using natural cubic splines.
We found that the response functions between incident postmenopausal breast cancer and maximum NDVI were consistent with linearity. The age-adjusted and fully-adjusted ORs, per increase in the interquartile range (IQR=0.13) of maximum NDVI measured with a 250 m buffer around residences, were 0.95 (95%CI: 0.86–1.04) and 1.00 (95%CI: 0.84–1.11), respectively. For maximum NDVI measured using a 1000 m buffer (IQR=0.05), these were 0.98 (95%CI: 0.94–1.02) and 0.99 (95%CI: 0.95–1.03), respectively.
Our findings suggest that exposure to NDVI evaluated where participants were interviewed is not associated with the risk of incident postmenopausal breast cancer.
Some evidence that exposure to greenness may improve health.
Little data that greenness is associated with the incidence of breast cancer.
The study is a population-based case-control of postmenopausal breast cancer.
No associations were found between greenness, measured by NDVI, and breast cancer.
Breast cancer is one of the most important diseases affecting women, with the age-adjusted incidence rate in 2020 being about 47.8 per 100,000 women . It is the most common cause of death from cancer, with a mortality rate of 13.6 per 100,000 (about 685,000 deaths per year) . The lifetime risk of women developing invasive breast cancer in the USA is about 13%, and about 3% of women will die of breast cancer .
Accepted risk factors account for 25–33% of all breast cancer cases, including increasing age, ethnicity, family history of breast cancer, previous breast disease, early age at menarche, hormonal replacement therapy, oral contraceptive use, alcohol consumption, physical inactivity, excess body weight, and oral contraceptive usage . Other factors that have been shown to be protective include early age at first full-term pregnancy and breastfeeding. Potential risk factors (e.g., environmental and occupational exposures) may also play a part in the etiology of breast cancer, such as exposure to diesel engine exhaust, other air pollutants, and tobacco smoke. Although hormonal factors are important, the pathogenic mechanisms are not well understood .
In several studies the association between levels of greenness in urban areas and health outcomes was investigated (e.g., ), and the overall findings suggest that greenness may be associated with positive effects on people’s psychological and physical health. Specifically, the health benefits appear to be conveyed by providing opportunities for outdoor activities, promoting social engagement, reducing ambient air pollution by absorption through the vegetation, and mitigating noise . Furthermore, as increased levels of greenness can encourage people’s participation in physical activities, it may help manage body weight and fight obesity, an accepted risk factor for postmenopausal breast cancer. Indeed, residential proximity to green space has been hypothesized to be related to the incidence of breast cancer and in this study, which to our knowledge is the only one to date, the risk of premenopausal and postmenopausal breast cancer combined was found to be negatively associated with greenness levels in urban neighborhoods. However, it is possible that a protective effect found in this study may be due to an inherent selection effect whereby people in higher socioeconomic brackets can afford to live in urban areas with parks and trees and, hence more greenness, and because of their higher socioeconomic standing they are in better health .
The objective of the present paper is to determine whether there is an association between past exposure to residential greenness, as measured by the normalized difference vegetation index (NDVI), and the incidence of invasive breast cancer among postmenopausal women living in Montreal, Quebec, in the mid-2000s. The present study is a population-based, case-control study designed originally to identify occupational and environmental risk factors for postmenopausal breast cancer. We have previously published results on ambient air pollution from this study .