The association between the incidence of post-menopausal breast cancer and residential greenness

1

Introduction

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 [21] . 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) [21] . 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 [3] .

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 [101320] . 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 [1314] .

In several studies the association between levels of greenness in urban areas and health outcomes was investigated (e.g., [1247] ), 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 [12] . 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 [16] 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 [11] .

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 [8] .