Low nadir CD4 cell count associated with increased cataract risk in South Africans taking HIV therapy

A low nadir (lowest ever) CD4 cell count is associated with increased lens density – a marker for cataract formation – in people with HIV, investigators report in the online edition of the Journal of Acquired Immune Deficiency Syndromes. The authors suggest that increased lens density may be an indicator of accelerated ageing in people with HIV.

“HIV-infected individuals receiving ART [antiretroviral therapy] and who had low nadir CD4 cell counts…have a greater risk of increased ocular lens density when compared with HIV-seronegative individuals,” write the researchers. “This provides corroborative evidence of accelerated aging and that this may be associated with delayed initiation of ART.”

Improvements in treatment and care mean that the prognosis of many people with HIV is now excellent. However, there is accumulating evidence that HIV is associated with acceleration in the ageing process. Increased rates of many of the diseases of ageing have been seen in people living with HIV.

The prevalence of cataracts – cloudiness in the lens of the eye – increases with age. It is therefore possible that people with HIV are vulnerable to cataract formation at an earlier age than would be otherwise expected.

An international team of investigators wanted to see if this was the case. They therefore designed a study comparing lens density – an accurate marker of cataract formation – involving 242 people living with HIV and 248 age-matched controls recruited in Cape Town, South Africa.

All were aged over 30 and none had a history of serious eye disease or had diabetes, which can lead to ocular damage.

Lens density was measured using densitometry imaging. This uses a 360-degree rotating non-contact camera that provides a rapid and precise three-dimensional view of the lens, cornea and anterior chamber.

Overall, the patients and controls were well matched, and had a mean age of approximately 41 years. However, patients with HIV were less likely to smoke and had lower alcohol consumption than the controls. Both of these factors have been associated with eye disease.

The majority of HIV-positive patients (88%) were taking antiretroviral therapy. The median duration of treatment was 59 months. The current median CD4 cell count among the patients taking therapy was 468 cells/mm³ and 84% had an undetectable viral load.

Overall, there was no difference in lens density measurements between the patients and controls. The median value for both groups was 9.8.

However, further analysis that took into account potential confounders, showed that patients on HIV treatment whose nadir CD4 cell count was below 200 cells/mm³ were more likely to have high lens density than HIV-negative individuals (p = 0.04).

This association between low nadir CD4 cell count and increased lens density was also significant when analysis was restricted to patients with HIV (p = 0.04).

“Low nadir CD4 count has been identified as an independent predictor of several premature age-related co-morbidities in HIV-infected individuals,” note the authors.

There was no association between current CD4 cell count and lens density. However, there was a non-significant trend suggesting that a detectable viral load despite HIV therapy increased lens density.

“We found HIV-infected individuals on ART with low nadir CD4 counts to have an increased risk of higher lens density compared to HIV-seronegative individuals,” conclude the authors. They suggest that early initiation of antiretroviral therapy could help prevent the accelerated ageing observed in people with HIV. “Premature aging may well have important socio-economic and healthcare implications for the many millions of people living with HIV long-term on ART in sub-Saharan Africa.”