Bone fractures more likely in an HIV-positive cohort than in the general US population: HOPS study

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Between the years 2000 and 2008, 4% of HIV-positive patients in the US HIV Outpatient Study experienced bone fractures – a significantly higher rate than that estimated in the general US population. The findings were presented by lead investigator Christine Dao of the Centres for Disease Control at a Thursday session of the17th Conference on Retroviruses and Opportunistic Infections (CROI).

This study investigated the incidence rates and types of bone fracture amongst patients in the HIV Outpatient Study (HOPS) – a prospective cohort study enrolling HIV-positive patients at ten clinics in eight US cities.

Data on reported fractures were taken from the medical records of 5826 patients from the years 2000 to 2008 (only first fractures were considered). The study patients had a median age of 40 and were 79% male, 52% white, 33% black and 73% antiretroviral therapy (ART)-experienced, with a median CD4 cell count of 372 cells/mm3).

Glossary

nadir

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

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.

opportunistic infection (OI)

An infection that occurs more frequently or is more severe in people with weakened immune systems, such as people with low CD4 counts, than in people with healthy immune systems. Opportunistic infections common in people with advanced HIV disease include Pneumocystis jiroveci pneumonia; Kaposi sarcoma; cryptosporidiosis; histoplasmosis; other parasitic, viral, and fungal infections; and some types of cancer. 

hazard

Expresses the risk that, during one very short moment in time, a person will experience an event, given that they have not already done so.

prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

During the interval from 2000 to 2008, fractures occurred in 236 (4%) of the study patients. On average, patients with fractures were slightly older (median 45 years) and about half were ART-experienced (55%)

To compare bone fractures in HOPS to those in the general US population, the study investigators approximated the overall national rates with data from the National Hospital Ambulatory Medical Care Survey (NHAMCS), which were weighted to produce national estimates from a sample of outpatient departments around the US.

In 2006, the frequency of all fractures among adults aged 25 to 54 years was greater among HOPS participants than in the US general population (as estimated using the NHAMCS), with 84.2 and 35.6 fractures per 10,000 people occurring in each respectively, adjusted for sex.

The investigators then examined the factors associated with an increased risk of fracture in HIV-positive patients seen between 2002 and 2008. Risk factors included:

  • age 47 years or more (adjusted hazard ratio [aHR] = 1.6 compared to age 35 or less, 95% confidence interval [CI],1.0–2.5),
  • lowest-ever (nadir) CD4 cell count below 200 cells/mm3 aHR = 1.6, 95% CI, 1.1–2.3),
  • co-infection with hepatitis C virus (aHR = 1.6, 95% CI, 1.1–2.3),
  • diabetes (aHR = 1.6, 95% CI, 1.1–2.6), and
  • substance abuse (aHR = 1.5, 95% CI, 1.0–2.6).

In conclusion, the investigators found that rates of bone fracture were higher in the HOPS cohort of HIV-positive patients than in adults presenting for outpatient care in the general US population, and that rates in HOPS appeared to be increasing. Further studies were suggested to directly compare HIV-positive patients to HIV-negative controls, to assess how HIV infection and HIV treatment affect risk of fracture, and to explore how bone density loss and bone fracture risk are related in individuals with HIV.

Further information

You can view the abstract on the official conference website.

You can also view a webcast and slides of this session on the official conference website.

References

Dao C et al. Higher and increasing rates of fracture among HIV-infected persons in the HIV Outpatient Study compared to the general US population, 1994 to 2008. 17th Conference on Retroviruses and Opportunistic Infections, San Francisco, abstract 128, 2010.