Table 2 Standardised incidence ratios for chronic obstructive pulmonary diseases in siblings by age at first hospitalisation

Age at diagnosis (years)	Men		Women		All
Age at diagnosis (years)	O	SIR (95% CI)	O	SIR (95% CI)	O	SIR (95% CI)
<50	75	7.00 (3.89 to 12.41)	61	6.59 (3.56 to 11.97)	136	6.81 (4.04 to 11.39)
50–59	96	5.29 (3.03 to 9.14)	135	5.21 (3.09 to 8.73)	231	5.25 (3.25 to 8.44)
≥60	90	3.69 (2.10 to 6.41)	97	3.15 (1.81 to 5.44)	187	3.39 (2.07 to 5.53)
All	261	4.90 (3.06 to 7.82)	293	4.44 (2.79 to 7.05)	554	4.65 (3.02 to 7.14)
Heterogeneity (χ², p value)	χ² = 17.76, p<0.01		χ2 = 24.94, p<0.01		χ2 = 24.54, p<0.01

O, observed number of cases; SIR, standardised incidence ratio; CI, confidence interval.
95% CI does not include 1.00.