A new study from the University of Eastern Finland shows that obese, postmenopausal women have an increased risk of hip fracture earlier in life. The results published in Osteoporosis International showed that women who had a higher body mass index (BMI) had a higher risk of hip fracture well before the age of 70.
For the study, researchers used information from OSTPRE, a population-based cohort study that was launched in 1989. Participants were recruited between 1932 and 1942 and had a 25-year follow-up. During this follow-up, researchers analyzed the association of BMI at the age of 58 with the risk of hip fracture up until the age of 70. This showed the prevalence of early fracture. They also analyzed the association of body mass index at the age of 70 with the risk of hip fracture later in life, up until the age of 83. There were two groups examined—normal weight and obese women.
Normal weight was defined as a BMI of 25 or less, overweight as a BMI of 25-29.9, and obesity as a BMI of 30 or over (kg/m2). At the beginning of the study, 39.6 percent of the women were normal-weight, 40 percent were overweight, and 19.9 percent were obese. As the women aged, there was some increase in BMI. By the age of 70, 33.4% of the women were normal-weight, 40.9% were overweight, and 25.7% were obese.
As was expected, researchers found that the risk of hip fracture increased with age in all groups. However, it was shown that the risk of early hip fracture increased faster in obese women and slower in overweight women compared to others in the group. In obese women, the probability of hip fracture was at 1% already at the age of 66.7, while in overweight women the 1% probability was reached 5.1 years later, at the age of 71.8. Obese women had a 2% probability of hip fracture 2.1 years earlier than overweight women and 4% probability 1.3 years earlier. As the women aged, the differences between the groups became smaller.
The study was able to conclude that in obese women, hip-fracture related mortality in five years after the incident was approximately 1.5 times higher compare to others.
Protection Against Hip Fracture
Previous studies had suggested that obesity could be a potential factor that helps to protect against bone loss and hip fracture. However, the findings of this study show that the association between BMI and fracture in postmenopausal women may be dependent on the age group being studied.
“Based on this study, the risk of early hip fracture occurring before the age of 70 is clearly highest in obese women – and especially in obese women who have a below-average bone density. Later, after around 75 years of age, the risk increases fastest in slender women. Aging women at the borderline between normal weight and overweight seem to have the lowest risk,” Senior Researcher Toni Rikkonen from the University of Eastern Finland concluded.