Fracture rates higher in patients with HIV

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Fracture rates in patients with HIV are higher than those in the general US population, investigators report in the online edition of Clinical Infectious Diseases. Rates increased between 2000 and 2002, and then remained broadly stable until the end of the study in 2008.

“Age-adjusted fracture rates among men and women aged 25-54 years in the HOPS [HIV Outpatient Study] were consistently higher than those in adults in the US general population.”

Older age was significantly associated with an increased risk of fracture, as were substance abuse, co-infection with hepatitis C virus, diabetes and a nadir CD4 cell count below 200 cells/mm3.

Glossary

nadir

Lowest of a series of measurements. For example, an individual’s CD4 nadir is their lowest ever measured CD4 count.

body mass index (BMI)

Body mass index, or BMI, is a measure of body size. It combines a person's weight with their height. The BMI gives an idea of whether a person has the correct weight for their height. Below 18.5 is considered underweight; between 18.5 and 25 is normal; between 25 and 30 is overweight; and over 30 is obese. Many BMI calculators can be found on the internet.

bone mineral density (BMD)

The higher your bone mineral content, the denser your bones are. And the denser your bones, the stronger they are and the less likely they are to break. A bone density test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. The bones that are most commonly tested are in the spine, hip and sometimes the forearm. 

diabetes

A group of diseases characterized by high levels of blood sugar (glucose). Type 1 diabetes occurs when the body fails to produce insulin, which is a hormone that regulates blood sugar. Type 2 diabetes occurs when the body either does not produce enough insulin or does not use insulin normally (insulin resistance). Common symptoms of diabetes include frequent urination, unusual thirst and extreme hunger. Some antiretroviral drugs may increase the risk of type 2 diabetes.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

The investigators believe that their results have clinical significance and call for HIV care to routinely consider patients’ risk of fractures and falls.

Low bone mineral density is common in patients with HIV, and some studies have suggested that fracture rates are increasing in this group.

Researchers from HOPS wanted to get a clearer understanding of fracture rates in patients with HIV.

They therefore compared fracture rates seen in 5826 patients who received care between 2000 and 2008 with those recorded in the general US population.

Data were also gathered on rates of fragility fractures (wrist, vertebra, hip), and the investigators conducted analyses to see if any factors were associated with an increased risk of fracture for patients with HIV.

Most (79%) of the patients were male, their median age was 40, over half (52%) were white, and 73% were taking antiretroviral therapy.

A total of 233 patients experienced a fracture. Fracture rates increased from 57 per 1000 person years in 2000 to 85 per 1000 person years in 2002. This increase was significant (p = 0.01).

Rates then remained broadly stable until the end of follow-up in 2008 (90 per 1000 person years).

In contrast, no change was observed in the fracture rate for the general US population between 2000 and 2006.

Patients aged between 25 and 54 constituted 87% of the HOPS population, and a significant increase in fracture rates (p = 0.01) was observed in these individuals over the course of the study.

Rates of fragility fractures were higher among both HIV-positive men and women than age-matched controls in the general US population.

HIV-positive men were significantly more likely to experience fractures of the wrist and vertebra (p < 0.01), and HIV-positive women experienced more fractures of the vertebra (p < 0.01) and hip (p = 0.04). 

Analysis showed that factors associated with an increased risk of fracture for patients with HIV were age over 47 (p = 0.05), a nadir CD4 cell count below 200 cells/mm3, co-infection with hepatitis C (p = 0.01), diabetes (p = 0.05) and substance abuse (p = 0.05).

Many of these are known risk factors for fracture.

However, the investigators note that the association with nadir CD4 cell count is new and unexplained and call for further studies to examine this association.

Risk factors for fragility fractures also included age and hepatitis C co-infection, as well as a body mass index (BMI) below 18.5 (adjusted hazard ratio, 3.72; 95% CI, 1.14-12.09).

“Our study suggests that HIV-infected adults, particularly adults aged 25-54 years, are at an increased risk of bone fracture, compared with the general population,” conclude the investigators.

They believe that their findings have implications for HIV care, commenting, “we recommend that screening for and correcting reversible causes of low BMD [bone mineral density] and fall risk be incorporated into routine clinical care of HIV-infected patients.”

References

Young B et al. Increased rates of bone fracture among HIV-infected persons in the HIV Outpatient Study (HOPS) compared with the US general population, 2000-2006. Clin Infect Dis, online edition: doi: 10.1093/cid/ciq242, 2011 (click here for the free abstract).