Exposure to greenness and light pollution and risk of ALS: a case-control study in Northern Italy

Abstract Background Amyotrophic lateral sclerosis (ALS) is a rare and progressive neurodegenerative disease that affects the upper and lower motor neurons. Although some new pharmacological treatments have become available in recent years, it is still fatal. Aside from some known genetic factors, the etiology is unknown, but the study of environmental factors showed that cigarette smoking, head trauma, and exposure to heavy metals and selenium, and pesticides may play a relevant role. More recently, environmental pollutants including greenness and night-time light pollution have been proposed. Methods In this population-based case-control study, we evaluated exposure to greenness by satellite data of the Normalized Difference Vegetation Index (NDVI), and light pollution through data from the Defense Meteorological Satellite Program (DMSP). We recruited ALS subjects with diagnosis in the period 1998-2012 in the provinces of Modena, Reggio Emilia and Parma, and up to four controls matched by sex, age and province of residence. Results and Discussion We found an inverse association between intermediate exposure (NDVI between 0.30-0.50) to urban greenness and ALS risk, but higher risk was noted at both lower and higher exposure. Possible mechanisms explaining the beneficial effect of greenness in neurodegenerative diseases may be the greater opportunity for physical activity and the reduction of concentrations of air pollutants, especially particulate matter and nitrogen dioxide. The analysis of light pollution using DMSP did not show any association with ALS risk, although more recent satellite data could be more sensitive and accurate in detecting differences in exposure not possible with DMSP data. Key messages • Intermediate exposure to greenness may be a protective factors for amyotrophic lateral sclerosis. • The association between light at night and amyotrophic lateral sclerosis risk do not demonstrate any association.