Table.
Annual admission rates per 1000 for twins and singletons born in Scotland 1981-4, admitted before age 10 years (n=number of liveborn children)
| Singletons | Twins | Rate ratio (95% CI) | |
|---|---|---|---|
| All twins and singletons: | (n=257 871) | (n=5068†) | |
| Asthma | 4.45 (11 464) | 2.11 (107) | 0.47 (0.39 to 0.57)*** |
| Acute bronchitis | 1.84 (4757) | 2.53 (128) | 1.37 (1.15 to 1.63)*** |
| Other respiratory diseases | 3.14 (8094) | 3.04 (154) | 0.97 (0.83 to 1.13) |
| All respiratory diseases | 9.43 (24 315) | 7.68 (389) | 0.81 (0.74 to 0.90)*** |
| Male twins versus male singletons: | (n=132 006) | (n=1896) | |
| Asthma | 5.62 (7418) | 2.11 (40) | 0.38 (0.28 to 0.51)*** |
| Acute bronchitis | 2.25 (2968) | 3.16 (60) | 1.41 (1.09 to 1.81)** |
| Other respiratory diseases | 4.05 (5341) | 4.01 (76) | 0.99 (0.79 to 1.24) |
| All respiratory diseases | 11.91 (15 727) | 9.28 (176) | 0.76 (0.68 to 0.90)*** |
| Female twins versus female singletons: | (n=125 865) | (n=1724) | |
| Asthma | 3.21 (4046) | 1.86 (32) | 0.58 (0.41 to 0.81)** |
| Acute bronchitis | 1.42 (1789) | 2.26 (39) | 1.59 (1.16 to 2.18)** |
| Other respiratory diseases | 2.19 (2753) | 2.26 (39) | 1.03 (0.76 to 1.41) |
| All respiratory diseases | 6.82 (8588) | 6.38 (110) | 0.94 (0.78 to 1.12) |
| Twins of different sex versus all singletons: | (n=257 871) | (n=1430) | |
| Asthma | 4.45 (11 464) | 2.45 (35) | 0.55 (0.40 to 0.76)*** |
| Acute bronchitis | 1.84 (4757) | 2.03 (29) | 1.10 (0.77 to 1.58) |
| Other respiratory diseases | 3.14 (8094) | 2.73 (39) | 0.87 (0.64 to 1.19) |
| All respiratory diseases | 9.43 (24 315) | 7.20 (103) | 0.76 (0.63 to 0.92)** |
Number of admissions up to age 10 years in parentheses.
**
P⩽0.01; ***P⩽0.001. †Includes nine pairs of unknown sex.