In a heterozygous state, however, that same SCN5A variant protects from cardiac arrhythmia in FinnGen (β = −0.48, P = 2 × 10−8, posterior inclusion probability = 0.996 (ref. 30), indicating probable causality), including atrial fibrillation (β = −0.62, P =  7 × 10−7). This evidence concerns the gene SCN5A and chronic obstructive pulmonary disease.