Table 3 Adjusted associations* between urban background pollutants and hospital admissions in Copenhagen for three outcomes (15 May 2001 to 31 December 2004)

Pollutant	IQR†	One-pollutant model‡	Two-pollutant models
Pollutant	IQR†	One-pollutant model‡	NC_tot+PM₁₀	NC_tot+PM_2.5	NC_tot+CO	NC_tot+NO₂	NC_tot+O₃
CVD hospital admissions (age ⩾65 years)§
			n = 605	n = 302	n = 657	n = 606	n = 264
NC¶_tot	3907	1.00 (0.99 to 1.02)	0.98 (0.96 to 1.01)	0.99 (0.95 to 1.03)	0.99 (0.97 to 1.02)	1.01 (0.98 to 1.03)	1.01 (0.96 to 1.06)
PM₁₀	13	1.03 (1.01 to 1.05)**	1.04 (1.02 to 1.06)**
PM_2.5	5	1.03 (1.01 to 1.06)**		1.03 (1.01 to 1.06)**
CO	120	1.02 (0.99 to 1.04)			1.02 (0.99 to 1.06)
NO₂	6	1.00 (0.98 to 1.03)				1.00 (0.96 to 1.03)
O₃	12	1.02 (0.95 to 1.09)					1.02 (0.95 to 1.10)
RD hospital admissions (age ⩾65 years)††
			n = 564	n = 310	n = 676	n = 622	n = 269
NC_tot	3907	1.04 (1.00 to 1.07)**	1.00 (0.96 to 1.05)	0.97 (0.89 to 1.05)	1.03 (0.98 to 1.07)	1.00 (0.95 to 1.05)	0.95 (0.87 to 1.04)
PM₁₀	13	1.06 (1.02 to 1.09)**	1.05 (1.01 to 1.10)**
PM_2.5	5	1.00 (0.95 to 1.05)		1.00 (0.95 to 1.06)
CO	120	1.04 (0.99 to 1.09)			1.02 (0.96 to 1.08)
NO₂	6	1.06 (1.01 to 1.12)**				1.06 (0.99 to 1.13)
O₃	12	0.92 (0.79 to 1.07)					0.90 (0.77 to 1.05)
Asthma hospital admissions (age 5–18 years)‡‡
			n = 559	n = 318	n = 691	n = 684	n = 274
NC_tot	3907	1.07 (0.98 to 1.17)	1.03 (0.92 to 1.15)	1.04 (0.85 to 1.28)	1.09 (0.99 to 1.21)	1.07 (0.96 to 1.19)	1.08 (0.87 to 1.35)
PM₁₀	13	1.02 (0.93 to 1.12)	1.01 (0.91 to 1.12)
PM_2.5	5	1.15 (1.00 to 1.32)		1.13 (0.98 to 1.32)
CO	120	1.00 (0.89 to 1.127)			0.94 (0.81 to 1.08)
NO₂	6	1.04 (0.92 to 1.18)				0.97 (0.83 to 1.14)
O₃	12	1.11 (0.78 to 1.58)					1.16 (0.80 to 1.69)

*Relative risks (RR) and 95% confidence intervals per IQR, adjusted for temperature, dew point, season, day of the week, influenza, public holidays for all three outcomes, and grass pollen and school holidays for asthma.
†IQR, interquartile range, difference between 75th and 25th percentile.
‡Sample size (n) for pollutants in the one-pollutant model is limited to days when NC_tot is available, the same as n in the two-pollutant model with NC_tot^.
§RR for 4-day average, mean (lag 0–3).
¶NC_tot, total number concentration of particles (6–700 nm in diameter).
**p<0.05.
††RR for 5-day average, mean (lag 0–4).
‡‡RR for 6-day average, mean (lag 0–5).
CVD, cardiovascular disease; RD, respiratory disease.