Obese and overweight middle-aged women run a higher risk of developing blood clots than those who are healthy, according to joint research by New Zealand and British universities.
The study of data from more than a million women in the United Kingdom found blood clotting was more prevalent in women who had a high body mass index (BMI) compared to those whose were considered in the healthy range with a BMI under 25.
The Otago University and Oxford University research looked at the risk of venous thromboembolism (VTE), a relatively rare, but potentially life-threatening condition, involving blood clots in the legs which sometimes break off and travel to the lungs.
The study, published in US journal Circulation this week, found the risk of VTE increased with higher BMI and rose after surgery.
"Surgery is known to increase the risk of VTE and our research shows that the risk of post-operative VTE is higher in women who are overweight or obese than it is in women who are a healthy weight," said lead author Otago University's Dr Lianne Parkin.
Researchers calculated that 12 weeks after surgery 4.8 in every 1000 women with a healthy BMI reading were admitted to hospital of died from VTE compared with 7.0 for those who were overweight or obese.
Dr Parkin says the heavier women are more likely to undergo surgery than those in a healthy weight range.
"So heavier women are more likely to have surgery, and they are more likely to develop blood clots following that surgery," she said.
The findings suggest that avoiding weight gain and even small weight reductions are likely to reduce the risk of VTE in middle-aged women, Dr Parkin says.