Environmental and Genetic Factors Associated With URI in the First 6 Months (n = 239 Infants)

FactornHR (95% CI)P
Cigarette exposurea541.15 (0.89–1.49).28
Day care attendanceb671.74 (1.44–2.11)<.0001
One or more sibling(s) in the homec861.07 (1.01–1.14).032
Breastfeeding exclusively for at least 6 mod220.63 (0.40–0.99).049
Length of breastfeeding, moe950.96 (0.93–0.99).0075
Length of time to exclusive formula feeding, mo2680.96 (0.93–0.98).0009
Length of time to other feeding, mof2710.97 (0.93–1.00).070
Born after February 2010g2200.84 (0.75–0.93).0012
TNFα−308 polymorphismh811.19 (0.69–1.01).063
IL-6–174 polymorphismh1271.06 (0.89–1.27).50
  • CI, confidence interval

  • a Any smoking in the household.

  • b Yes/no, any length of time.

  • c Linear function, taking into account the number of siblings.

  • d The length 6 mo was chosen because it optimized the model fit to the data (ie, maximized the likelihood).

  • e Length of breastfeeding, not necessarily exclusively.

  • f Other food than breast milk or formula.

  • g Heptavalent PCV (7) was given before February 2010; all subjects received PCV13 thereafter. Of the subjects completing the study, 73% had received 4 doses of PCV vaccines, 18% received 3 doses, 5% received 2 doses, and 3% received only 1 dose.

  • h Homozygous and heterozygous.