Table 3 Results from systematic reviews relating relative risk for asthma to factors. This list is not intended to be exhaustive but serves to illustrate that each factor has a relatively modest association in isolation. What is unknown is whether relative risks are additive or multiplicative when more than one factor is present for an individual
Risk factor for developing childhood asthmaRelative risk [95% CI]Comment
Either parent smoke [25]1.37 [1.15–1.64]
Maternal asthma [26]3.04 [2.59–3.56]
Paternal asthma [26]2.44 [2.14–2.79]
Atopy [27]1.5 to 4.8
Antenatal paracetamol exposure [28]1.28 [1.16–41]
Dog exposure [29]1.14 [1.01–1.29]1.39 [1.00, 1.95] for any furry pet
Cat exposure [29]0.72 [0.55–0.93]
Breast feeding [19]0.70 [0.60–0.81]Lower in atopic families (OR 0.52)
Visible mould [30]1.49 [1.28–1.72]Mould derived compounds may reduce risk
High maternal vitamin D during pregnancy [20]0.56 [0.42–0.73]Wheezing outcomes not asthma
High maternal vitamin E during pregnancy [20]0.68 [0.52–0.88]Wheezing outcomes not asthma
Mediterranean diet during pregnancy [20]0.22 [0.08–0.58]Wheezing outcomes not asthma