Table 2.

Hazard ratios (HRs (95% CI)) for IHD associated with different exercise and commuting habits among persons with different air pollution exposure at home addresses

Exercise in training clothes	Overall model with no interaction effects	Proportional hazard p- value*	Adjusted† HRs in categories of high and low particle exposure				Adjusted† interaction HR
			Low PM10‡	Proportional hazard p- value*	High PM10‡	Proportional hazard p- value*	Benefits of exercise/commuting comparing high and low particle exposure	Proportional hazard p- value*
Never	1		1		1
≤Once/week	1.03 (0.90 to 1.16)	0.35	1.01 (0.84 to 1.21)	0.67	1.04 (0.88 to 1.23)	0.35	1.03 (0.81 to 1.32)	0.75
≥Twice/week	0.76 (0.62 to 0.93)	0.08	0.99 (0.76 to 1.29)	0.47	0.55 (0.40 to 0.76)	0.24	0.56 (0.37 to 0.84)	0.65
			Low PM2.5§		High PM2.5§
Never			1		1
≤Once/week			1.03 (0.86 to 1.23)	0.78	1.03 (0.87 to 1.22)	0.30	1.00 (0.78 to 1.28)	0.61
≥Twice/week			0.94 (0.72 to 1.22)	0.69	0.60 (0.44 to 0.82)	0.09	0.64 (0.43 to 0.96)	0.30
Active commuting per season			Low PM10‡		High PM10‡
Non-active commuting	1		1		1
≤Two seasons of four	1.01 (0.86 to 1.19)	0.50	1.17 (0.93 to 1.47)	0.35	0.88 (0.70 to 1.11)	0.70	0.76 (0.55 to 1.04)	0.34
>Two seasons of four	0.87 (0.76 to 0.998)	0.85	0.93 (0.76 to 1.14)	0.48	0.82 (0.68 to 0.98)	0.89	0.88 (0.67 to 1.15)	0.53
			Low PM2.5§		High PM2.5§
Non-active commuting			1		1
≤Two seasons of four			1.18 (0.94 to 1.49)	0.43	0.87 (0.69 to 1.10)	0.76	0.73 (0.53 to 1.01)	0.43
>Two seasons of four			0.97 (0.80 to 1.19)	0.37	0.79 (0.65 to 0.95)	0.89	0.81 (0.62 to 1.06)	0.44

*P-value of the Schoenfeld residual test of proportional hazards.

†Adjusted for sex, calendar year, education, smoking, alcohol intake, occupation, neighbourhood mean income, leisure time physical activity and active commuting.

‡Low PM₁₀: ≤9.6 µg/m³; high PM₁₀: >9.6 µg/m³.

§Low PM_2.5: ≤5.7 µg/m³; high PM_2.5: >5.7 µg/m³.

IHD, ischemic heart disease.