Published on July 4 in The Lancet, the controversial study, which is attracting widespread attention in the UK media, looks at health outcomes of the tightly knit Pakistani community of Bradford, Northern England.
From cohort data on 5,127 babies born between 2007 and 2011, researchers found that 37 per cent were born to first-cousin parents and that six per cent had a congenital anomaly, such as heart defects and neurological disorders.
While researchers reported that ‘consanguinity was associated with a doubling of risk for congenital anomaly’ and that ‘31 per cent of all anomalies in children of Pakistani origin could be attributed to consanguinity’, Professor Bittles said the issue was much more complicated.
“While this study offers an important source of detailed information, appropriate caution is needed in formulating conclusions without a clear consideration of cultural factors, in this case biraderi membership,” Professor Bittles said.
Similar to the Hindu caste system, and clans and tribes in Arab societies, biraderi play a major role in occupational and social networks, including arrangements of marriage.
“The Pakistani community of Bradford cannot be regarded as uniform, as it is separated along very clear traditional lines of class.
“Given that most do not marry outside their class, the probability of an inherited illness is increased; this makes it unlikely that 31 per cent of congenital defects can be attributed to parental consanguinity alone.
“We have to consider community traditions as part of the wider picture.”
Professor Bittles said that socioeconomic factors had to be rigorously examined as well, noting that more than two-thirds of the cohort fell into the most deprived fifth of the English population.
“Given that some of these same issues have been raised in terms of close-knit communities in Australia, looking more deeply at the contributory factors certainly has relevance,” he added.
The study did raise a number of findings that Professor Bittles called ‘puzzling’, including an apparent lower prevalence of congenital defects in children whose mothers smoked 11–20 cigarettes per day shortly before or during pregnancy as well as for those who drank alcohol.