A comprehensive account of intra-familial marriage, its genetic effects and common misconceptions has been written by a Murdoch University researcher.
Adjunct Professor Alan Bittles from Murdoch’s Centre for Comparative Genomics has spent 35 years researching the effect of consanguineous (or same blood) marriages on health outcomes and intellectual and development disabilities.
In Consanguinity in Context, which will be published by Cambridge University Press on May 7, Prof Bittles provides an overview of the topic and critical analyses of the influence of consanguinity on health.
“There are more than 1100 million people worldwide who are married to a close relative or are the offspring of such a marriage, living in regions where 20 to 50 per cent of marriages are between blood relatives, so these types of marital unions are in no way rare,” said Prof Bittles.
“They are common in many Muslim, Buddhist, Christian, Hindu and Jewish communities and migration means their incidence is on the rise in many Western cultures including Australia, the UK and the United States.
“The general belief is that first cousin marriages lead to negative genetic outcomes, yet a large majority of children born to first cousins are healthy. A global analysis has shown that early death or major ill-health is on average four to five per cent higher in children of first cousins than equivalent non-consanguineous offspring.
“This is a complicated topic. Our findings over years of research have shown that the health risks associated with consanguineous marriage have been exaggerated, largely due to flawed research design, with a failure to allow for non-genetic factors that can adversely influence health outcomes. For example, many of the countries in which first or second cousin marriage is more common are afflicted with poverty which can have a devastating effect on early health and development.”
Prof Bittles said more research was urgently needed into the outcomes of consanguineous marriages because of the number of people involved and he hopes his book could be a catalyst for this work.
“The central aim in my work is the prevention of genetic disease through a better understanding and appreciation of how genes are transmitted within families and communities,” he said.
“In my book I discuss consanguinity and disorders of adulthood – the first review of its kind which is particularly relevant given the ageing of the global population. But more work in this area is needed.
“To date the principal disease focus has been on early childhood, with an emphasis on disorders such as congenital heart defects. As yet there has been very little work focused on possible health outcomes of common adult disease states, such as coronary heart disease and diabetes.”
As well as analysing scientific data, Prof Bittles provides detailed information on past and present religious and social attitudes to consanguineous marriages in his book. The related legal practices and prohibitions are also examined and the final three chapters deal in detail with practical issues including genetic testing, education and counselling, national and international legislation and the future of consanguineous marriage worldwide.
“My major intention with this book was to produce a reasoned and balanced overview of the topic which should both be readable to members of the general public but at the same time provide appropriately detailed information for scientists and clinicians,” he said.
Consanguinity in Context can be ordered online and e-versions will also be available after its launch on May 7.