A ground-breaking overseas study on cot death may shed light on why Hong Kong has such a low incidence of the syndrome, doctors say. Heart experts at Italy's University of Pavia found between 25 per cent and 30 per cent of such deaths were caused by a rare disease called long-QT syndrome, an electrical abnormality in the heart. The condition affects about one person in 10,000 in the West and is caused by genetic mutations. The Italian team published its results last week in the New England Journal of Medicine. Dr Cheung Pik-to, an associate professor in Hong Kong University's department of paediatrics, said genetic factors could account for the low number of cases of sudden infant death syndrome in Hong Kong. 'We can't rule out genetic factors playing a role,' he said. 'We expect to learn more about the genetic basis of QT-syndrome with the completion of the human genome project.' Dr Cheung said international figures on sudden infant death syndrome - also called cot death - showed Hong Kong had 0.2 deaths in 1,000 babies, compared with 0.7 in Britain, 1.4 in New Zealand and 0.8 in the US. The incidence rates were almost double in the West in the 1980s until physicians taught parents to lay babies on their backs, traditional practice in Hong Kong, rather than on their stomachs, a position which may block their breathing. Even accounting for this, Dr Cheung said, Hong Kong still had a low incidence.