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Table 3 Adjusted odds ratios (OR) and 95% confidence intervals (CI) of having or having had an allergy by presence of secondhand tobacco smoke early in life and presence of parental allergy in 4-year old children, Malmö, Sweden

From: Early exposure to secondhand tobacco smoke and the development of allergic diseases in 4 year old children in Malmö, Sweden

No parent with an allergy

At least one parent with an allergy

Secondhand tobacco smoke at 0-4 weeks of age*

Secondhand tobacco smoke at 0-4 weeks of age*

No

Yes

No

Yes

OR; 95% CI*

OR; 95% CI*

OR; 95% CI*

OR; 95% CI*

1.00†

0.96 (0.50, 1.81)§

4.31 (3.07, 6.97)§

7.69 (4.46, 13.25)§¶

Secondhand tobacco smoke at 8 months of age*

Secondhand tobacco smoke at 8 months of age*

No

Yes

No

Yes

OR; 95% CI*

OR; 95% CI*

OR; 95% CI*

OR; 95% CI*

1.00†

1.15 (0.63, 2.07)§

4.34 (3.06, 6.17)§

6.10 (3.51, 10.59)§

  1. * OR, odds ratio; CI, confidence interval; Secondhand tobacco smoke at 0-4 weeks and 8 months were categorized into no (no secondhand tobacco smoke at all) and yes (daily secondhand tobacco smoke, including smoking outside).
  2. † Reference level.
  3. ‡ Parents reporting that the child had or have had allergic diseases (i.e., atopic eczema, hay fever, asthma or food allergies). Those reporting confirmed allergies (tested positive in skin prick test, in blood test and by provocation) or having severe allergies were considered as having an allergy.
  4. § Adjusted for sex, year, maternal smoking during pregnancy, maternal educational level, parents' country of birth, taken part of parental education program, crowded living and having a pet.
  5. ¶ Statistically significantly different (p < 0.05) from the category: At least one parent with an allergy and no secondhand tobacco smoke.