Vertebral compression fractures are the most common type of osteoporotic fractures and are associated with significant disability, morbidity, and mortality. Anyone who has had one will tell you that the pain can be severe and may last for months. In many cases only part of the vertebral body collapses, giving the vertebra a wedge-like shape. When this occurs in the mid or thoracic spine it causes the spine to bend forward giving the patient a stooped posture. Twenty five percent of post-menopausal women in the US are estimated to have had a vertebral fracture, and that figure increases with advancing age. Diuretics (water pills) have long been thought to play a role in osteoporosis and its related fractures.
Recently a study was published about diuretic use and vertebral fractures. It used data from the Nurses’ Health Study, an ongoing study that began in 1976 and has enrolled 121,700 nurses aged 30-55 years. The analysis used data from 2002 and 2012 from 55,780 women who answered a questionnaire that was mailed to them. The respondents were asked about their use of thiazide diuretics (HCTZ, Hygroton) and loop diuretics (Lasix, furosemide) and their history of fractures. Thiazide diuretics are used in treating hypertension and heart disease and in older US adults. Hydrochlorothiazide or HCTZ is the second most commonly prescribed medication. Thiazide diuretics decrease urinary calcium excretion thereby improving calcium balance but may cause hyponatremia (low serum sodium). A number of studies have linked hyponatremia to an increased fracture risk. On the other hand loop diuretics, used mostly for heart disease and heart failure, increase urinary calcium excretion, which could lower bone mineral density, but rarely cause hyponatremia.
The study found that women who took thiazide or loop diuretics had a one-and-a-half time greater risk of vertebral fracture. This result was surprising in that thiazides, because of their positive effect on calcium balance, were long thought to not be associated with fractures. The authors concluded that the increased fracture risk with thiazides was due to the side effect of hyponatremia. A low serum sodium activates osteoclasts, which are bone cells that break down bone, thereby thinning the bone and making fracture more likely. Loop diuretics were also associated with an increased fracture risk as was expected because they cause loss of calcium. Interestingly however was that thiazides caused an increased risk of vertebral fractures but a decreased risk of hip fractures. This difference between spine and hip fracture risk was thought to be from differences in mechanical loading, geometry, bone microarchitecture, and other factors.
Other risk factors for osteoporosis were looked at and these include smoking, low calcium intake, low BMI (small, thin women), low or no physical activity, and race (white and Asian women have a higher risk). If you have osteoporosis or have an increased risk of developing it and are taking diuretics you might want discuss your use of them with your doctor. Remember too that thiazides can have other negative health consequences like raising blood sugar and lipid levels. But please always talk to your doctor before discontinuing any medication that you are taking.
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