Umeå University's logo

BACKGROUND: Promotion of active commuting provides substantial health and environmental benefits by influencing air pollution, physical activity, accidents, and noise. However, studies evaluating intervention and policies on a mode shift from motorized transport to cycling have estimated health impacts with varying validity and precision.

OBJECTIVE: To review and discuss the estimation of air pollution exposure and its impacts in health impact assessment studies of a shift in transport from cars to bicycles in order to guide future assessments.

METHODS: A systematic database search of PubMed was done primarily for articles published from January 2000 to May 2016 according to PRISMA guidelines.

RESULTS: We identified 18 studies of health impact assessment of change in transport mode. Most studies investigated future hypothetical scenarios of increased cycling. The impact on the general population was estimated using a comparative risk assessment approach in the majority of these studies, whereas some used previously published cost estimates. Air pollution exposure during cycling was estimated based on the ventilation rate, the pollutant concentration, and the trip duration. Most studies employed exposure-response functions from studies comparing background levels of fine particles between cities to estimate the health impacts of local traffic emissions. The effect of air pollution associated with increased cycling contributed small health benefits for the general population, and also only slightly increased risks associated with fine particle exposure among those who shifted to cycling. However, studies calculating health impacts based on exposure-response functions for ozone, black carbon or nitrogen oxides found larger effects attributed to changes in air pollution exposure.

CONCLUSION: A large discrepancy between studies was observed due to different health impact assessment approaches, different assumptions for calculation of inhaled dose and different selection of dose-response functions. This kind of assessments would improve from more holistic approaches using more specific exposure-response functions.

Introduction: A protective role of leisure time physical activity with regard to non-communicable chronic diseases (NCDs) is well established. However, shapes of dose-response relationships and the extent of BMI mediation between physical activity and disease risk are not well known. Furthermore, the knowledge about risk reductions from active commuting is limited. Methods: Meta-analyses of prospective cohort studies published from January 1990 to June 2019 were conducted, 1) to assess the effect of leisure time and commuting physical activity on cardiovascular disease (CVD), type 2 diabetes, breast cancer and colon cancer, and 2) to quantify the extent to which adjustment for BMI affect these relations. Results: Random effect meta-analyses of 59 prospective cohort studies estimated that individuals who engaged in 11.25 MET-hours/week of active commuting had a decreased risk of myocardial infarction (MI) by 18% (95% CI: 1-33%) and type 2 diabetes by 22% (95% CI: 4-37%) compared with non-commuters. Corresponding risk reductions for leisure-time physical activity (LTPA) were 22% for MI, 26% for CVD, 27% for heart failure, 23% for stroke, 22% for type 2 diabetes, 15% for colon cancer and 7% for breast cancer. Except for breast cancer, adjustment for BMI reduced the benefit of physical activity. Conclusion: Both active commuting and LTPA are associated with lower risk for NCD. Currently, available data is insufficient to establish detail and reliable dose-response curves.

OBJECTIVE: To assess a possible interaction effect between physical activity and air pollution on first incidence of ischaemic heart disease (IHD).

DESIGN: Prospective cohort study.

SETTING: Umeå, Northern Sweden.

PARTICIPANTS: We studied 34 748 adult participants of Västerbotten Intervention Programme cohort from 1990 to January 2014. Annual particulate matter concentrations (PM_2.5 and PM₁₀) at the participants' residential addresses were modelled and a questionnaire on frequency of exercise and active commuting was completed at baseline. Cox proportional hazards modelling was used to estimate (1) association with physical activity at different levels of air pollution and (2) the association with particulate matter at different levels of physical activity.

OUTCOME: First incidence of IHD.

RESULTS: Over a mean follow-up of 12.4 years, there were 1148 IHD cases. Overall, we observed an increased risk of IHD among individuals with higher concentrations of particles at their home address. Exercise at least twice a week was associated with a lower risk of IHD among participants with high residential PM_2.5 (hazard ratio (HR) 0.60; 95% CI: 0.44 to 0.82) and PM₁₀ (HR 0.55; 95% CI: 0.4 to 0.76). The same beneficial effect was not observed with low residential PM_2.5 (HR 0.94; 95% CI: 0.72 to 1.22) and PM₁₀ (HR 0.99; 95% CI: 0.76 to 1.29). An increased risk associated with higher long-term exposure to particles was only observed among participants that exercised in training clothes at most one a week and among those not performing any active commuting. However, only the interaction effect on HRs for exercise was statistically significant.

CONCLUSION: Exercise was associated with a lower risk of first incidence of IHD among individuals with higher residential particle concentrations. An air pollution-associated risk was only observed among those who exercised less. The findings support the promotion of physical activity and a mitigation of air pollution.

We aimed to assess a possible interaction effect between physical activity and particulate air pollution exposure on recurrence of ischemic heart disease (IHD) and stroke. We followed 2221 adult participants comprising first time IHD (1403) and stroke (818) cases from the Västerbotten Intervention Program between 1 January 1990 to 31 December 2013. During mean follow-up times of 5.5 years, 428 and 156 participants developed IHD and stroke recurrence, respectively. PM2.5 concentrations above the median (5.48 µg/m3) were associated with increased risk of IHD and stroke recurrence by 13% (95% CI −17–45%) and 21% (95% CI −19–80%), respectively. These risk increases were however only observed among those that exercised at most once a week at 21% (95% CI −5– 50%) and 25% (95% CI −19–90%) for IHD and stroke recurrence, respectively. Higher frequency of exercise at recruitment was positively associated with IHD and stroke recurrence but only the association with IHD recurrence among participants with low residential PM2.5 was statistically significant (96% increased risk (95%-CI 22–215%)). However, no interaction effect between physical activity and PM2.5 exposure was found. Our findings suggest that physical activity may reduce the air pollution exposure associated risk for recurrent cardiovascular disease, likely by reducing the inflammatory response.