However, an increased risk was seen in the subgroup of non-smoking women ≥60 years old (though with broader confidence interval), most likely due to reduced power in our analyses compared to when analyzing presence (≥1 copy) vs. absence (0 copies) of GSTM1. This gene dosage effect nevertheless strengthens the possibility that there is a real association between GSTM1 CNV and risk for RA in this subset of older non-smoking women. The gene discussed is GSTM1; the disease is rheumatoid arthritis.