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Table 2 Associations between month of birth and risk of hospitalisation for asthma by 12-months

From: Pollen exposure in pregnancy and infancy and risk of asthma hospitalisation - a register based cohort study

  Crude Standard adjustment Adjustment for LRTI exposure Adjustment for pollen exposure Adjustment for both LRTI & pollen exposure
Season of birth OR aOR* Δ† aOR** Δ† aOR** Δ†   Δ†
Feb/Mar 1 1 - 1 - 1 - 1 -
Apr/May 1.01 (0.81-1.27) 1.02 (0.81-1.28) 0.7% 1.00 (0.78-1.28) −1.4% 1.09 (0.84-1.41) 7.8% 1.08 (0.83-1.41) 6.6%
Jun/Jul 1.05 (0.84-1.32) 1.06 (0.85-1.34) 1.1% 1.03 (0.80-1.31) −2.6% 0.78 (0.57-1.05) −26.3% 0.78 (0.58-1.06) −25.5%
Aug/Sep 1.11 (0.89-1.40) 1.15 (0.91-1.44) 3.3% 1.04 (0.78-1.39) −6.3% 0.86 (0.63-1.19) −22.3% 0.88 (0.62-1.25) −20.9%
Oct/Nov 1.63 (1.31-2.02) 1.59 (1.28-1.97) −2.5% 1.41 (1.03-1.93) −13.5% 1.33 (0.95-1.87) −18.0% 1.35 (0.91-2.00) −17.2%
Dec/Jan 1.30 (1.04-1.62) 1.25 (1.00-1.56) −3.6% 1.16 (0.87-1.55) −10.6% 1.16 (0.81-1.66) −10.5% 1.15 (0.79-1.70) −10.9%
  1. All ORs are in comparison to children born in February to March (the period with the lowest observed risk).
  2. * Adjusted for year of birth, maternal smoking, infant gender and gestational age.
  3. ** Also adjusted for pollen exposure (as a linear exposure) during the first and third trimester and during the first three months of infancy.
  4. All changes are relative to the unadjusted ORs in the table above. Positive values indicate an increase in the association, while negative values indicate a reduction in the OR.