Respiratory and cardiovascular responses to walking down a traffic-polluted road compared with walking in a traffic-free area in participants aged 60 years and older with chronic lung or heart disease and age-matched healthy controls: a randomised, crossover study

Abstract

Background: Long-term exposure to pollution can lead to an increase in the rate of decline of lung function, especially in older individuals and in those with chronic obstructive pulmonary disease (COPD), whereas shorter-term exposure at higher pollution levels has been implicated in causing excess deaths from ischaemic heart disease and exacerbations of COPD. We aimed to assess the effects on respiratory and cardiovascular responses of walking down a busy street with high levels of pollution compared with walking in a traffic-free area with lower pollution levels in older adults.

Methods: In this randomised, crossover study, we recruited men and women aged 60 years and older with angiographically proven stable ischaemic heart disease or stage 2 Global initiative for Obstructive Lung Disease (GOLD) COPD who had been clinically stable for 6 months, and age-matched healthy volunteers. Individuals with ischaemic heart disease or COPD were recruited from existing databases or outpatient respiratory and cardiology clinics at the Royal Brompton & Harefield NHS Foundation Trust and age-matched healthy volunteers using advertising and existing databases. All participants had abstained from smoking for at least 12 months and medications were taken as recommended by participants' doctors during the study. Participants were randomly assigned by drawing numbered disks at random from a bag to do a 2 h walk either along a commercial street in London (Oxford Street) or in an urban park (Hyde Park). Baseline measurements of participants were taken before the walk in the hospital laboratory. During each walk session, black carbon, particulate matter (PM) concentrations, ultrafine particles, and nitrogen dioxide (NO2) concentrations were measured.

Findings: Between October, 2012, and June, 2014, we screened 135 participants, of whom 40 healthy volunteers, 40 individuals with COPD, and 39 with ischaemic heart disease were recruited. Concentrations of black carbon, NO2, PM10, PM2.5, and ultrafine particles were higher on Oxford Street than in Hyde Park. Participants with COPD reported more cough (odds ratio [OR] 1·95, 95% CI 0·96-3·95; p<0·1), sputum (3·15, 1·39-7·13; p<0·05), shortness of breath (1·86, 0·97-3·57; p<0·1), and wheeze (4·00, 1·52-10·50; p<0·05) after walking down Oxford Street compared with Hyde Park. In all participants, irrespective of their disease status, walking in Hyde Park led to an increase in lung function (forced expiratory volume in the first second [FEV1] and forced vital capacity [FVC]) and a decrease in pulse wave velocity (PWV) and augmentation index up to 26 h after the walk. By contrast, these beneficial responses were attenuated after walking on Oxford Street. In participants with COPD, a reduction in FEV1 and FVC, and an increase in R5-20 were associated with an increase in during-walk exposure to NO2, ultrafine particles and PM2.5, and an increase in PWV and augmentation index with NO2 and ultrafine particles. In healthy volunteers, PWV and augmentation index were associated both with black carbon and ultrafine particles.

Interpretation: Short-term exposure to traffic pollution prevents the beneficial cardiopulmonary effects of walking in people with COPD, ischaemic heart disease, and those free from chronic cardiopulmonary diseases. Medication use might reduce the adverse effects of air pollution in individuals with ischaemic heart disease. Policies should aim to control ambient levels of air pollution along busy streets in view of these negative health effects.

Funding: British Heart Foundation.

Copyright © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.

Figures

Figure 1

Time course of health outcomes measurements Pink shading indicates timing of measurements.

Figure 2

Distribution of black carbon, nitrogen dioxide (NO2), noise, ultrafine particles, PM2.5 and PM10 concentrations, temperature, and relative humidity on the visit days to Oxford Street or to Hyde Park Box plots with 95% CIs. PM=particulate matter. **p

Figure 3

Odds ratio of getting worse symptoms of cough, sputum, shortness of breath, wheeze, sweat, and total scores for all these symptoms at Oxford Street versus Hyde Park for healthy volunteers and participants with COPD or IHD COPD=chronic obstructive pulmonary disease. IHD=ischaemic heart disease.

Figure 4

Change in FEV1 % of predicted value (A), and FVC % of predicted value (B) from the baseline (time 0) and at 1 and 2 h after the start of the walk in Oxford Street or Hyde Park followed by measurements performed back in the laboratory at times indicated after the start of the walk for healthy volunteers and participants with COPD or IHD Data are percentage changes (95% CI). COPD=chronic obstructive pulmonary disease. IHD=ischaemic heart disease. FEV1=forced expiratory volume in the first second. FVC=forced vital capacity. *p<0·05, **p<0·01, ***p<0·001, comparing Oxford Street with Hyde Park. +p<0·05, ++p<0·01, +++p<0·001, compared with timepoint 0.

Figure 5

Respiratory resistance at 5 Hz (A; R5) and at 20 Hz (B; R20), and differential frequency-dependent respiratory resistance at 5 Hz and 20 Hz measured by impulse oscillometry (C; R5–20) from baseline (time 0) and at 4 h and 26 h after the start of the walk in Oxford Street or in Hyde Park for healthy volunteers and participants with COPD or IHD Data are percentage changes (95% CI). COPD=chronic obstructive pulmonary disease. IHD=ischaemic heart disease. *p

Figure 6

Pulse wave velocity (A), augmentation index (B), systolic blood pressure (C), and in heart rate (D) from the baseline (time 0) and at 1 and 2 h after the start of the walk on Oxford Street or in Hyde Park followed by measurements performed back in the laboratory at times indicated after the start of the walk for healthy volunteers and participants with COPD or IHD Data are percentage changes (95% CI). COPD=chronic obstructive pulmonary disease. IHD=ischaemic heart disease. *p

Figure 7

Changes in FEV1 (% predicted value) and FVC (% predicted value; A), in differential frequency-dependent respiratory resistance at 5Hz and 20Hz (R5-20, B) and in pulse wave velocity and augmentation index (C) per IQR changes in components of air pollution at the times indicated after the start of the 2 h walk in two exposure sessions for healthy volunteers and participants with COPD or IHD Data are percentage changes (95% CI). BC=black carbon (per 9·2 μg/m3). NO2=nitrogen dioxide (per 64·9 ppb). UFP=ultrafine particle number concentration (per 19 854/cm3). PM2.5=particles <2·5 μM in diameter (per 14·94 μg/m3). PM10=particles <10 μM in diameter (per 14·47 μg/m3). FEV1=forced expiratory volume in the first second. FVC=forced vital capacity. COPD=chronic obstructive pulmonary disease. IHD=ischaemic heart disease. PWV=pulse wave velocity. AI=augmentation index. Noise per 3·97 dB.

Figure 8

Effect of medication on cardiovascular responses in participants with IHD (A) and (B) show the responses in PWV and AI in participants with IHD stratified according to taking or not taking cardiovascular medication. (C) Shows the sensitivity analysis of the association between PWV and AI per IQR changes in components of air pollution at the times indicated after the start of the 2 h walk in two exposure sessions in the two subgroups of IHD participants. In the 78 walks of the 39 IHD participants, 49 walks were done with participants taking oral medication on that day, with the remaining 29 walks with participants not using medication. IHD=ischaemic heart disease. PWV=pulse wave velocity. AI=augmentation index. BC=black carbon (per 9·2 μg/m3). NO2=nitrogen dioxide (per 64·9 ppb). UFP=ultrafine particle number concentration (per 19 854/cm3). PM2.5=particles <2·5 μM in diameter (per 14·94 μg/m3). PM10=particles <10 μM in diameter (per 14·47 μg/m3). * p<0·05. ***p<0·001.