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Table 2 Lifetime cumulative ETS exposure in a population-based sample of adults aged 55–75 years

From: Lifetime environmental tobacco smoke exposure and the risk of chronic obstructive pulmonary disease

Source of ETS exposure COPD (n = 386) No COPD (n = 1,727) P value
Prenatal ETS* 32 (8.3%) 96 (5.6%) 0.051
Cumulative lifetime home ETS    <0.0001
   Quartile 1 (0–9 yrs) 70 (18%) 443 (26%)  
   Quartile 2 (10–21 yrs) 72 (19%) 461 (27%)  
   Quartile 3 (22–41 yrs) 86 (22%) 451 (26%)  
   Quartile 4 (≥42 yrs) 158 (41%) 372 (22%)  
Cumulative lifetime work ETS    0.0002
   Quartile 1 & 2 (0–5 yrs) 163 (42%) 881 (51%)  
   Quartile 3 (6–22 yrs) 93 (24%) 440 (25%)  
   Quartile 4 (≥23 yrs) 130 (34%) 406 (24%)  
  1. Proportions are column proportions (of those with and without COPD)
  2. P-values from the likelihood ratio chi-square test
  3. *Mother smoked during pregnancy
  4. First and second quartile were both zero, so they were combined into one group.