British and US scientists have found the first clear evidence that genetics plays a role in sudden infant death syndrome (Sids).
The study focused on mutations in the SCN4A gene which helps regulate the muscular control of breathing.
Defects in the gene are associated with a range of neuromuscular disorders, some potentially life-threatening, that make breathing or speaking difficult. Typically SCN4A mutations are very rare, occurring in fewer than five people in every 100,000. But the study uncovered harmful mutant versions of the gene in four of 278 cot death victims.
Having one of the gene variants may leave some children with weaker breathing muscles, said the researchers.
Faced with extra stresses to breathing such as tobacco smoke, getting entangled in bedding, or a minor illness or airway obstruction, they may be less able to correct their breathing, cough or catch their breath.
Professor Michael Hanna, from the Medical Research Council Centre for Neuromuscular Diseases at University College London, said: “More research will be needed to confirm and fully understand this link.”