Poor lower-limb strength common in patients with long-term HIV infection, French study finds

Over half of middle-aged HIV-positive patients in a large French cohort had poor lower-limb strength, French investigators report in the online edition of AIDS.

They warn that this could mean the patients have a higher risk of falls and recommend that assessments of lower-limb strength should be carried out as part of routine HIV care.

Problems with balance and a deterioration of muscle strength in the lower limbs (locomotor performance) are associated with ageing. Many patients with HIV are now living into older age, and the diseases of ageing are an increasingly important cause of illness and death in these individuals.

Research conducted in 2002 showed that up to 30% of HIV-positive individuals had problems with muscle strength or balance. 

Investigators from the French Agency for AIDS and Hepatitis Research (ANRS) CO3 Aquitaine Cohort wished to gain a better understanding of locomotor performance in HIV-positive patients in the modern treatment era.

They therefore designed a cross-sectional (or 'snap-shot') study involving 324 patients who received care between 2007 and 2009.

Locomotor function was assessed using six validated tests:

• An assessment of overall balance.
• Distance walked in six minutes at an accelerated speed.
• Time to stand up from an armchair, walk three metres, turn around, walk back to chair and sit down.
• Reach test.
• Static balance test.
• Five-times sit-to-stand test, an assessment of the amount of time needed to stand up from a sitting position five times. This assesses lower-limb strength.

The patients had a median age of 48, and 80% were men. They had been living with HIV for a long time, and the median period since diagnosis was almost 13 years. Consistent with this, 83% of patients were taking HIV therapy and their median CD4 cell count was 520 cells/mm³.

Over half (53%) of individuals had a poor five-times-sit-to-stand result. “The poor…performance was considerably higher in our sample than the expected frequency in the general population,” comment the researchers.

In addition, 24% of patients performed poorly on the walking assessment, 11% had poorer than expected reach, and 10% had impaired balance.

Of the 172 patients with poor sit-to-stand results, 90 also had poor result in at least one of the other assessments.

“Eighty-four percent of patients with poor six-minute walk performance also had poor performance in the [five-times sit-to-stand] test,” note the investigators.

Surprisingly, poor performance in the sit-to-stand assessment was more common in younger patients. Results showed that 64% of individuals under 50 performed poorly in this assessment compared to only 36% of patients aged over 50. This difference was highly significant (p < 0.001).

Given the high prevalence of poor performance in the sit-to-stand assessment, the investigators restricted their statistical analysis to the factors associated with this measure of lower limb strength.

Their first analysis showed that poorer performance was associated with a range of risk factors, including: younger age (p < 0.0001), female sex (p < 0.01), injecting drug use (p < 0.01), hepatitis C co-infection (p = 0.02), smoking (p < 0.01), a lower body mass index (p = 0.01), longer duration of infection with HIV (p < 0.0001), and therapy with a 'd-drug' (ddI, d4t or ddC) (p < 0.001).

However, their final multivariate model, which controlled for potential confounders, showed that only body mass index (p < 0.001) and longer duration of infection with HIV (p < 0.001) were associated with poor lower-limb strength.

The effect of body mass index differed according to age. A low body mass index was associated with poor performance in younger patients. However, the opposite was true for older patients. Nevertheless, the investigators believe that in both older and younger patients the underlying reason was low muscle mass in the legs and buttocks.

Each year of infection with HIV increased the risk of poor performance by 8%.

There was some suggestion that HIV therapy that included a d-drug was also associated with poor lower-limb strength, but this fell short of statistical significance. Nevertheless, the investigators believe that this finding “may warrant further exploration.”

“Given the high frequency of poor [five-times sit-to-stand] performance...we recommend to perform [this] test in standard care,” write the authors, who conclude with a call for longitudinal studies “to asses the evolution of locomotor performance and the incidence of falls and their impact on fractures in the HIV-infected population.”