Table 5.

Adjusted hazard ratios for the development of symptoms for childhood ETS exposure, childhood lower respiratory infections, pack-years of smoking before onset of symptoms, and family history of emphysema

Risk factor	Cough	Wheeze	Dyspnea
Childhood ETS	2.11 (1.18–3.76)	1.26 (0.83–1.92)	1.00 (0.62–1.59)
Pack-years: 1–10	2.16 (1.18–3.96)	1.90 (1.10–3.30)	1.29 (0.63–2.60)
Pack-years: 11–20	1.00 (0.50–2.00)	1.51 (0.91–2.49)	2.35 (1.34–4.12)
Pack-years: 21–30	1.19 (0.63–2.24)	1.61 (0.98–2.65)	2.71 (1.48–4.97)
Pack-years: >30	1.23 (0.58–2.61)	1.15 (0.62–2.13)	2.20 (1.14–4.21)
Family history	1.26 (0.81–1.98)	1.72 (1.20–2.47)	1.30 (0.85–2.15)
Childhood respiratory infections	1.30 (0.84–1.99)	1.49 (1.05–2.11)	1.45 (0.97–1.98)

Abbreviations: ETS, environmental tobacco smoke.

Note: Bold indicates statistical significance.