Table 4 Adjusted associations* between urban background pollutants and hospital admissions in Copenhagen for three outcomes (15 May 2001 to 31 December 2004)
PollutantIQR†One-pollutant model‡Multi-pollutant models
Four size modesPM10+a212
CVD hospital admissions (age ⩾65 years)§
n = 676n = 564
PM10131.03 (1.01 to 1.05)**1.05 (1.01 to 1.09)**
NC10032591.00 (0.98 to 1.02)
NC¶a123420.99 (0.97 to 1.01)0.99 (0.97 to 1.02)
NCa2317860.99 (0.96 to 1.01)0.99 (0.96 to 1.02)
NCa5730261.01 (0.98 to 1.02)0.99 (0.97 to 1.02)
NCa2124951.02 (1.00 to 1.04)**1.02 (1.00 to 1.05)**0.98 (0.95 to 1.01)
RD hospital admissions (age ⩾65 years)††
n = 701n = 564
PM10131.05 (1.02 to 1.09)**1.04 (0.98 to 1.11)
NC10032591.03 (0.99 to 1.07)
NCa123421.01 (0.98 to 1.05)1.01 (0.97 to 1.05)
NCa2317860.99 (0.94 to 1.03)0.98 (0.94 to 1.03)
NCa5730261.04 (1.00 to 1.08)**1.02 (0.97 to 1.06)
NCa2124951.04 (1.01 to 1.08)**1.03 (0.99 to 1.07)1.01 (0.96 to 1.07)
Asthma hospital admissions (age 5–18 years)‡‡
n = 722n = 559
PM10131.02 (0.93 to 1.12)0.94 (0.81 to 1.09)
NC10032591.06 (0.97 to 1.16)
NCa123421.08 (0.99 to 1.18)1.07 (0.97 to 1.19)
NCa2317861.09 (0.98 to 1.21)1.08 (0.97 to 1.21)
NCa5730261.02 (0.94 to 1.12)0.93 (0.83 to 1.04)
NCa2124951.08 (1.00 to 1.17)**1.12 (1.02 to 1.23)**1.10 (0.96 to 1.13)

  • *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 NCtot is available.

  • §RR for 4-day average, mean (lag 0–3).

  • ¶NC, number concentration of particles; a12, size mode with median diameter of 12 nm; a23, size mode with median diameter of 23 nm; a57, size mode with median diameter of 57 nm; a212, size mode with median diameter of 212 nm.

  • **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.