Risk/benefit tradeoff of habitual physical activity and air pollution on chronic pulmonary obstructive disease: findings from a large prospective cohort study

Table 5 Combined effects of habitual physical activity, long-term PM_2.5 exposure, and COPD incidence in the UK Biobank

PA levels ^a	PM_2.5 levels (HR, 95% CI) ^a,^b			RERI ^c		P for interaction ^d
PA levels ^a	High	Moderate	Low	Moderate PM_2.5 level	Low PM_2.5 level
Self-reported PA						0.805
Low	1.000	1.026 (0.909, 1.159)	0.955 (0.840, 1.085)
Moderate	0.792 (0.711, 0.881)	0.753 (0.674, 0.840)	0.747 (0.667, 0.836)	− 0.01 (− 0.18, 0.17)	0.02 (− 0.14, 0.19)
High	0.745 (0.668, 0.831)	0.736 (0.658, 0.822)	0.681 (0.607, 0.764)	0.01 (− 0.16, 0.18)	0.02 (− 0.15, 0.19)
Objectively measured PA						0.998
Low	1.000	1.088 (0.885, 1.337)	0.923 (0.740, 1.152)
Moderate	0.755 (0.592, 0.963)	0.790 (0.620, 1.006)	0.735 (0.573, 0.943)	− 0.05 (− 0.35, 0.25)	0.06 (− 0.23, 0.34)
High	0.693 (0.527, 0.911)	0.653 (0.492, 0.866)	0.574 (0.432, 0.764)	− 0.13 (− 0.44, 0.18)	0.02 (− 0.14, 0.19)

Abbreviations: HR hazard ratio, CI confidence interval, RERI relative excess risk due to interaction, PA physical activity, PM_2.5 particulate matter with aerodynamic diameter < 2.5 μm, COPD chronic obstructive pulmonary disease
^a: PM_2.5 exposure levels (low, moderate, and high) were defined by PM_2.5 tertiles (< 9.48 μg/m³, 9.48 to 10.27 μg/m³, and ≥10.27 μg/m³), self-reported PA levels were defined according to a standard scoring criteria of International Physical Activity Questionnaire (IPAQ): low (< 600 MET-min/week), moderate (600 to 3000 MET-min/week), and high (≥3000 MET-min/week), and objectively measured PA levels were defined by objectively measured PA tertiles (< 24.32 milli-gravity (mg), 24.32 to 30.70 mg, and ≥ 30.70 mg)
^bAll results were calculated based on covariates in Model 3: age at enrolment, sex, ethnicity, BMI, education, household income, employment status, smoking status, alcohol drinking, fruit and vegetable intake, secondhand smoke exposure, and Townsend deprivation index
^c The estimates of RERI were calculated based on the reference group with high level of PM_2.5 exposure and low level of PA
^d Likelihood tests were applied to test the significance of interaction term by comparing the model with and without the interaction term

ISSN: 1741-7015