Lowering Blood Pressure but Raising the Risk of Hip Fracture

Abstract & Commentary

By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips serves on the speakers bureau for PotomaCME.

This article originally appeared in the March 15, 2013, issue of Internal Medicine Alert. It was edited by Stephen Brunton, MD, and peer reviewed by Gerald Roberts, MD. Dr. Brunton is Adjunct Clinical Professor, University of North Carolina, Chapel Hill, and Dr. Roberts is Senior Attending Physician, Long Island Jewish Medical Center, NS/LIJ Health Care System, New Hyde Park, NY. Dr. Brunton serves on the advisory board for Abbott, Boehringer Ingelheim, Janssen, Novo Nordisk, Sanofi, Sunovion, and Teva; he serves on the speakers bureau of Boehringer Ingelheim, Janssen, Novo Nordisk, Sanofi, Sunovion, and Teva. Dr. Roberts reports no financial relationship to this field of study.

Synopsis: The risk of hip fracture goes up for about 6 weeks immediately after older people start taking antihypertensives.

Source: Butt DA, et al. The risk of hip fracture after initiating antihypertensive drugs in the elderly. Arch Intern Med 2012; 172:1739-1744.

Taking antihypertensive drugs is known to be associated with increased risk of falling and hip fracture in older people, but most of what is known about this is based on studies done in people who are taking these medications chronically. These authors set out to learn about the risk of falls and hip fractures immediately after initiation of antihypertensive drugs in community-dwelling people.

To do this, they identified all Ontario residents aged 66 years and older who got a first prescription for a thiazide diuretic, angiotensin II converting-enzyme (ACE) inhibitors, angiotensin II receptor antagonist/blockers (ARBs), a calcium channel blocker, or a beta-adrenergic blocker. They linked these patients to the national physician claims database, which provides detailed diagnostic and procedural information. Because of the richness of these data, they were able to exclude patients who were prescribed these agents for something other than hypertension (for example, cardiomyopathy or essential tremor). They also excluded those who were previously prescribed these drugs at any point in the preceding year, those with pathologic fractures, and those who were institutionalized. The main outcome was first occurrence of a hip fracture. They compared incidence of hip fracture in the first 45 days after a new antihypertensive prescription with two 45-day periods in the year before they started the treatment.

The cohort had a mean age of 81 years and was mostly women (about 81%). ACE inhibitors were the most commonly prescribed agents (30%), with ARBs being the least-commonly used (5%). There were 301,591 newly treated hypertensive elderly patients who had 1463 hip fractures during the 10-year period of data collection.

People who started an antihypertensive drug for the treatment of hypertension had a 43% increased risk of hip fracture during the first 45 days of treatment. The risks were generally consistent among the five different classes of antihypertensive drugs, but only the ACE inhibitors and beta-blockers were statistically significantly associated with increased risk as a class. Comparing risk of hip fractures for the first 2 weeks to the next 4 weeks after starting the drug showed that the hip fracture risk after starting any antihypertensive drug for the treatment of hypertension was actually highest (54%) for weeks 3-6. This increased trend was not seen with thiazide diuretics and was most pronounced for ACE inhibitors. Statistically controlling for various confounders, including psychotropic medications, did not affect these relationships.

Commentary

What is new here is the finding that the risk of hip fracture increases immediately after starting a new antihypertensive agent in older people, particularly for ACE inhibitors and beta-blockers. The authors discuss several different mechanisms, including orthostatic hypotension, confusion, venous pooling, and extracellular volume decreases, depending on the agent.

In their discussion, the authors note that treating hypertension reduces the risk of cardiovascular disease in the long run but increases the risk of fall-related injuries in the short run. They note that such falls cause functional, cognitive, and physical effects similar to those that result from myocardial infarction and stroke.1,2 In fact, they point out that the incidence of nonfatal cardiovascular events in hypertensive elderly patients and serious fall injuries in the elderly at risk of falls is essentially the same, at 16%.2,3 All of a sudden, the decision of when and how to treat hypertension in the elderly is not as simple as it was. At the very least, we need to advise our older patients that they will be slightly more likely to break a hip in the first 6 weeks after starting a new drug for hypertension.

References

1. Gill TM, et al. Restricted activity among community-living older persons: Incidence, precipitants, and health care utilization. Ann Intern Med 2001;135:313-321.

2. Tinetti ME, et al. Risk factors for serious injury during falls by older persons in the community. J Am Geriatr Soc 1995;43:1214-1221.

3. Staessen JA, et al. Risks of untreated and treated isolated systolic hypertension in the elderly: Meta-analysis of outcome trials. Lancet 2000;355:865-872.