Risk of asthma in relation to atopy, education, social class, leisure time physical activity, domestic animals, and smoking history in 262 twin pairs discordant for medicated asthma (univariate analysis)
| Men | Women | Dizygotic | Monozygotic | All | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A/B | RR (95% CI) | A/B | RR (95% CI) | A/B | RR (95% CI) | A/B | RR (95% CI) | RR (95% CI) | |||||
| Atopy1-151 | 23/12 | 1.92 (0.95 to 3.85) | 44/11 | 4.00 (2.07 to 7.75)1-150 | 51/16 | 3.19 (1.82 to 5.59)1-150 | 12/7 | 1.71 (0.68 to 4.35) | 2.91 (1.81 to 4.68)1-150 | ||||
| Education1-151 | 5/15 | 0.33 (0.12 to 0.92)1-150 | 8/14 | 0.57 (0.24 to 1.36) | 11/18 | 0.61 (0.29 to 1.29) | 2/8 | 0.25 (0.05 to 1.18) | 0.45 (0.23 to 0.86)1-150 | ||||
| Social class1-152 | |||||||||||||
| Workers | 22/19 | 1.31 (0.64 to 2.68) | 22/26 | 0.91 (0.47 to 1.77) | 33/34 | 1.05 (0.61 to 1.82) | 8/6 | 1.36 (0.40 to 4.62) | 1.08 (0.67 to 1.75) | ||||
| Farmers | 11/6 | 2.06 (0.73 to 5.84) | 13/7 | 1.73 (0.63 to 4.73) | 16/7 | 2.30 (0.91 to 5.85) | 3/4 | 0.85 (0.18 to 4.16) | 1.91 (0.92 to 3.93) | ||||
| Physical activity1-151 | 15/25 | 0.60 (0.32 to 1.14) | 12/24 | 0.50 (0.25 to 1.00)1-150 | 14/36 | 0.39 (0.21 to 0.72)1-150 | 9/7 | 1.29 (0.48 to 3.45) | 0.55 (0.34 to 0.88)1-150 | ||||
| Pet animals1-151 | 20/26 | 0.77 (0.43 to 1.38) | 23/23 | 1.00 (0.56 to 1.78) | 32/31 | 1.03 (0.63 to 1.69) | 6/14 | 0.43 (0.17 to 1.12) | 0.88 (0.58 to 1.32) | ||||
| Smoking1-152 | |||||||||||||
| Former | 13/19 | 0.52 (0.22 to 1.28) | 10/18 | 0.59 (0.25 to 1.42) | 16/27 | 0.57 (0.28 to 1.17) | 6/5 | 0.84 (0.19 to 3.69) | 0.58 (0.31 to 1.06) | ||||
| Current | 19/20 | 0.67 (0.30 to 1.49) | 21/15 | 1.13 (0.54 to 2.40) | 30/25 | 0.95 (0.51 to 1.75) | 5/8 | 0.57 (0.14 to 2.26) | 0.88 (0.51 to 1.51) | ||||
| Pack years1-154 | 1.01 (0.98 to 1.04) | 1.10 (1.01 to 1.21)1-150 | 1.02 (0.99 to 1.06) | 0.98 (0.90 to 1.07) | 1.03 (0.99 to 1.06) | ||||||||
| Number of pairs | 125 | 137 | 179 | 60 | 262 | ||||||||
↵1-150 Statistically significant.
↵1-151 Risk ratios calculated for dichotomised variables as follows: atopicv non-atopic; higher educationv lower; conditioning physical activityv others; pet ownersv others.
↵1-152 Risk ratios calculated for categorised variables as follows: workersv others; ex-smokersv others, etc.
↵1-154 Pack years smoked at baseline in 1975. Four pairs in which one or both twins had missing data on pack years are excluded.
A = number of positively discordant twin pairs (twin with asthma during follow up had the determinant (e.g. atopy) at baseline whereas co-twin without asthma during follow up did not); B = number of negatively discordant twin pairs (twin with asthma did not have determinant (e.g. atopy) at baseline whereas co-twin without asthma had it).
23 pairs of unknown zygosity were excluded from risk ratio calculations by zygosity.
Risk ratio for unclassified occupation was 0.87 (95% CI 0.37 to 2.07) based on 11/14 pairs.