Environmental exposures, that is factors shared by large groups of people and extending beyond individual lifestyle, are receiving growing attention in dementia research. A new study by Jens Soeterboek and colleagues from the Alzheimer Centre Limburg (Maastricht University), published in Environmental Research, examines whether exposure to environmental noise is linked to cognitive functioning and structural markers of brain damage. The researchers used cross-sectional data from 4023 participants of the Maastricht Study, a population-based cohort originally designed to investigate type 2 diabetes. Participant information was linked with detailed environmental exposure data from the Geoscience and Health Cohort Consortium (GECCO).
These data captured cumulative mixed exposure to environmental noise from road traffic, railways, aviation, industry and wind turbines, averaged within a 50 by 50 metre area surrounding each participant’s residence. Participants also reported their own perceived noise exposure from the workplace, their neighbourhood or traffic environment. Cognitive functioning was assessed through a comprehensive neuropsychological test battery that measured processing speed, executive functioning, memory and attention. Structural brain health was evaluated using MRI derived volumes of grey matter, white matter and cerebrospinal fluid. The analyses also incorporated several important contextual factors, including a compound measure of socioeconomic position that combined educational attainment, occupation and household income. Degree of urbanisation and a brain healthy lifestyle score, quantified using the Lifestyle for Brain Health (LIBRA) index, were included as covariates.
The study reported no associations between objectively measured environmental noise exposure and performance in any of the cognitive domains. However, self-reported noise in the work environment showed consistent links with poorer memory, slower processing speed, reduced executive functioning and lower global cognition scores. In contrast to the cognitive findings, the brain imaging results indicated subtle structural differences related to noise exposure. Specifically, higher levels of environmental noise exposure were associated with lower white matter volume and higher cerebrospinal fluid volume, a pattern that may reflect greater brain atrophy. The authors concluded that objectively measured environmental noise exposure does not appear to affect cognitive performance directly. However, its associations with several markers of brain structure and the consistent links with self-reported noise at work highlight the importance of considering both objective and subjective aspects of noise exposure. They note that longitudinal studies will be needed to determine whether these structural differences develop over time and whether reducing noise exposure could contribute to promoting long term brain health.
https://www.sciencedirect.com/science/article/pii/S016041202500683X?via%3Dihub