What’s Behind the Decrease in the Rate of Hip Fractures?
In a study published in JAMA Internal Medicine, researchers showed how analysis of data from the multigenerational Framingham Osteoporosis Study – an ancillary study of the Framingham Heart Study – may explain, at least in part, why the incidence of hip fracture in the US has declined during the last 2 decades.
Some experts have attributed the change in the rate of hip fractures to improved treatments for osteoporosis, but the new study, which analyzes 40 years of data, has a different conclusion: The study authors found an association between the lower hip fracture rate and decreases in smoking and heavy drinking. These results indicate that modifiable lifestyle factors, along with treatments, may be beneficial to bone health.
The analysis included information from 4918 men and 5634 women who have participated in the Framingham Study. These individuals were followed for a first hip fracture between January 1, 1970, and December 31, 2010. The rates for hip fractures, which were adjusted for age, dropped by 4.4% each year across the 40-year study period. The decrease was seen in men and women.
The change in the rate of hip fractures was too significant to be explained by osteoporosis treatment alone, especially given that decreases were occurring before the availability of effective treatments for osteoporosis.
With that in mind, the researchers carefully examined decades of hip fracture data, which allowed statistical differentiation of changes in the incidence of hip fractures arising from the year of birth, aging, and the time period in which the data was collected. They found that a reduction in smoking and excessive alcohol consumption explained some of the declines in hip fracture rates, emphasizing that ongoing public health considerations help to prevent fractures.
The rate of smoking decreased from 38% in the 1970s to 15% in the period from 2006 to 2010. During the same period, heavy drinking (defined as 3 or more drinks per day) fell from 7% to 4.5%. The rates of other risk factors for hip fracture, such as underweight and early menopause, did not change over the study period.
“This study points to the continued need for public health interventions to target modifiable lifestyle factors such as smoking and drinking, in addition to considering osteoporosis treatments in individuals at risk of hip fractures,” said Timothy Bhattacharyya, MD, a researcher with the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).
Initially launched in 1948 to understand the epidemiology of cardiovascular disease, the Framingham Heart Study has become a treasure trove of data for epidemiologists searching for factors that contribute to many conditions that impact public health, including hip fractures. An estimated 150,000 hip fractures occur each year in the US, with estimated costs of care between $10.3 billion and $15.2 billion.
There are some limitations to this study. Because the data are exclusively from white individuals, it is unclear whether other populations might show a similar correlation between hip fracture rates and lifestyle factors. Framingham participants also had lower rates of obesity than the national average. In addition, the study did not include measurements of bone mineral density, because such testing was not available until the 1990s.
Swayambunathan J, Dasgupta A, Rosenberg PS, Hannan MT, Kiel DP, Bhattacharyya T. Incidence of hip fracture over 4 decades in the Framingham Heart Study. JAMA Intern Med. 2020 Jul 27. doi: 10.1001/jamainternmed.2020.2975. Online ahead of print.