Recent studies have suggested cardiovascular disease (CVD) and osteoporotic fractures may share a common etiology. There have been studies which show that bisphoshonates used to prevent the progression of osteoporosis also prevent the development of atherosclerosis. Other studies have linked cholesterol-lowering statins that reduce the risk of CVD to a reduction in the risk of osteoporotic fractures.
Ulf Sennerby, MD and colleagues examine the relationship between cardiovascular disease and the risk of hip fracture in a study published in the October 21 issue of JAMA. The results of their co-twin study showed a significant association between the two diseases suggesting possible genetic factors.
The researchers used information on 31,936 twins born from 1914 to 1944 in the Swedish Twin Registry. Only15,968 pairs were still alive in 1972 and were eligible for this study. The National Patient Registry was then used to identify twins with CVDs and fractures from 1964 and 2005. Twins were entered into the study when they turned 50 and followed up until the date of a first hip fracture, death, or the end of the study (Dec 31, 2005).
The crude absolute rate of hip fractures was found to be 12.6 per 1000 person-years after a diagnosis of either heart failure or stroke, 6.6 per 1000 person-years after a diagnosis of peripheral atherosclerosis, and 5.2 per 1000 person-years with a diagnosis of ischemic heart disease. This dropped to 1.2 per 1000 person-years for those twins with no diagnosis of CVD.
A multivariable-adjustment of the data was done taking into account such factors as body mass index, hormone therapy, impaired balance, alcohol use, smoking, physical activity, and medications. The multivariable-adjusted hazard ration (HR) of hip fracture after a diagnosis of heart failure was 4.40. After a stroke, the HR was 5.09. After a diagnosis of peripheral atherosclerosis, the HR was 3.20, and after an ischemic heart disease event, the HR was 2.32.
Identical twins without heart failure and stroke also had, after their co-twins had been exposed to these respective diseases, an increase rate of hip fracture. These sibling twins pseudoexposed for heart failure had a multivariable-adjusted HR of 3.74 for hip fracture, whereas pseudoexposure for stroke had an HR of 2.29.
Looking at the 10-year absolute risks of hip fracture, the researchers found women at all ages and those in all CVD categories had a higher risk than men. The average 75-year old woman had an 18% risk of a hip fracture within 10 years after diagnosis of heart failure compared to a 10% for a man of the same age. A 75-year-old woman with a stroke had a 10-year risk of hip fracture of 19% compared to a 15% risk for a man of the same age.
The researchers write “We advocate that individuals with a recent diagnosis of CVD should have their future fracture risk evaluated with clinical risk factors and bone scans.” They conclude “genetic predisposition is probably a major determinant of the excess fracture rate.”
Cardiovascular Diseases and Risk of Hip Fracture; JAMA, October 21, 2009, Vol 302, No 15, pp 1666-1673; Ulf Sennerby MD, Hakan Melhus MD PhD, Rolf Gedeborg MD PhD, Liisa Byberg PhD, Hans Garmo PhD, Anders Ahlbom PhD, Nancy L Pedersen PhD, Karl Michaelsson MD PhD