Multiple environmental factors and cardiovascular disease

Air pollution, transportation noise and low greenness have been associated with incidence of myocardial infarction (MI) and stroke in single exposure models. However, few studies have explored them simultaneously. Furthermore, socioeconomic deprived groups have been suggested to face a higher environmental burden, and may also be more vulnerable to environmental pollution, which could lead to increased health disparities. Therefore, the overall aim of this thesis was to assess the associations between long-term exposure to air pollution, traffic noise and greenness, and incidence of MI and stroke, in single- and multiple-exposure models, accounting for sociodemographic and lifestyle determinants.

A total of 20,407 women included in the Swedish Mammography Cohort (SMC), living in Uppsala County, Sweden, born between 1914 and 1948, were followed between 1997 and 2017 by linking spatiotemporally assessed long-term exposure to air pollution, road traffic noise and greenness, sociodemographic data from registers and lifestyle variables from questionnaire surveys. In study I, we prospectively assessed the associations between a set of individual and area- level sociodemographic variables and individual exposure to particles (PM2.5 and PM10), nitrogen dioxide (NO2), road traffic noise and greenness (NDVI in 500 m) using a fully time-varying model. Our results provide evidence of a diverse pattern of environmental-health disparities among different sociodemographic subgroups in urban settings.

Study II, is based on pooled cross-sectional data from the NordSOUND project including eleven Nordic cohorts and up to 177,566 participants with overweight and obesity data. We assessed exposure-response relationships of long-term exposure to road traffic, railway and aircraft noise, and overweight, obesity and central obesity. Our findings provide evidence of an association between road traffic and railway noise, and obesity; a potential causal pathway connecting noise exposure to cardiovascular disease (CVD).

Studies III and IV were based on the same time-varying data from the SMC, which were assessed in study I in conjunction with register data on MI and stroke. The aim was to assess associations of multiple environmental exposures and incidence of MI and stroke, respectively, in both single- and multi-exposure models, taking both individual- and area-level socioeconomic factors into account. We observed an inverse association between residential greenness and risk of MI in multi-exposure models. Air pollution, primarily fine particles (PM2.5), was associated with an increased stroke risk, accounting for co-exposures. We also found some evidence of a higher vulnerability in certain groups of the population, for instance in low educated women.

In conclusion, the four constituent papers of this thesis provide novel insights into sociodemographic inequalities in relation to residential environmental exposures in a sample of Swedish women. Moreover, the combination of air pollution, road traffic noise and greenness, and the time-varying data on both exposures and covariates, allowed us to assess associations with CVD in a unique setting. It can be concluded from the results that already at relatively low levels of air pollution, detrimental cardiovascular effects may occur. This was indicated by consistently elevated risks of stoke in relation to long-term PM2.5 exposure, as well as by increased risk of MI in low-educated women. Interestingly, greenness appeared to be associated with a lower risk of MI, adjusted for air pollution and noise. Finally, we were able to provide evidence of a potential pathway via obesity from transportation noise to CVD. Although, we did not observe an increased risk of MI and stroke in the SMC, possibly a consequence of overall low exposure levels and exposure misclassification.

It is our hope that the findings of this thesis may help to guide future recommendations and regulations on these environmental factors to protect human health.

List of scientific papers

I. Stucki L, Betnér S, Selander J, Lõhmus M, Åkesson A, Eriksson C. Sociodemographic inequalities in long-term exposure to air pollution, road traffic noise, and greenness: A population-based cohort study of women. Environ Epidemiol. 2023 Dec 1;7(6):e279. https://doi.org/10.1097/ee9.0000000000000279

II. Persson Å, Pyko A, Stucki L, Ögren M, Åkesson A, Oudin A, Tjønneland A, Rosengren A, Segersson D, Rizzuto D, Helte E, Andersson EM, Aasvang GM, Gudjonsdottir H, Selander J, Christensen JH, Leander K, Mattisson K, Eneroth K, Barregard L, Stockfelt L, Albin M, Simonsen MK, Spanne M, Roswall N, Tiittanen P, Molnár P, Ljungman PLS, Männistö S, Yli-Tuomi T, Cole-Hunter T, Lanki T, Lim YH, Andersen ZJ, Sørensen M, Pershagen G, Eriksson C. Long-term exposure to transportation noise and obesity: A pooled analysis of eleven Nordic cohorts. Environ Epidemiol. 2024 Jul 8;8(4):e319. https://doi.org/10.1097/ee9.0000000000000319

III. Stucki L, Helte E, Axelsson Ö, Selander J, Lõhmus M, Åkesson A, Eriksson C. Long-term exposure to air pollution, road traffic noise and greenness, and incidence of myocardial infarction in women. Environ Int. 2024 Aug 190:108878. https://doi.org/10.1016/j.envint.2024.108878

IV. Stucki L, Helte E, Axelsson Ö, Selander J, Lõhmus M, Åkesson A, Eriksson C. Long-term exposure to air pollution, road traffic noise and greenness, and incidence of stroke in women. [Manuscript]