People living with HIV under the age of 50 lose lung function faster than HIV-negative people, a review of a large US cohort has shown. People with a previous low CD4 cell count also had faster declines in lung function.
The findings were presented at the 2020 Conference on Retroviruses and Opportunistic Infections. Conference presentations are taking place online to minimise the risk of coronavirus transmission.
Lung function can decline for a variety of reasons. Lung function declines in everyone as they age but smokers and people who are obese will suffer greater declines in lung function. Asthma and chronic obstructive pulmonary disease (COPD) are the most common forms of lung disease, but many conditions can cause loss of lung function.
COPD refers to chronic obstructive bronchitis and emphysema. These conditions limit the flow of air into the lungs and the uptake of oxygen from the lungs into the bloodstream, leading to coughing, shortness of breath and wheezing. COPD is a progressive condition and smoking is the most common cause.
Although some studies have found an association between smoking and COPD in people with HIV, not all studies have been able to confirm that smoking behaviour explains an increased prevalence of abnormal lung function in people with HIV.
To investigate the impact of HIV-related factors on lung function, researchers from Johns Hopkins University Bloomberg School of Public Health and the University of North Carolina at Chapel Hill designed a longitudinal cohort study (SHIELD, Study of HIV Infection in the Etiology of Lung Disease). The study recruited 2216 participants (1168 HIV negative) with a median age of 50 years. Two-thirds were male, 85% were black and 79% were current smokers with an average of 19 pack-years of smoking history at baseline.
Smoking was more common in HIV-negative people (85% vs 72%), who also had a longer smoking history (20 vs 17 pack-years).
Lung function was measured using the FEV1 and FVC tests and was lower at baseline in people with HIV than HIV-negative people (FEV1, 2.59 vs 2.84 litres; FVC 3.46 vs 3.79 litres).
Participants underwent lung function tests semi-annually from 2009 to 2017.
The investigators modelled the average decline from the age of 40 in people under 50, and the average decline from the age of 60 in people over 50.
In under-50s, FEV1 declined faster in people with HIV than in those without HIV (-46ml/year vs 32ml/year) and people with HIV also started with lower FEV1 levels (-133ml lower). In HIV-negative people, FEV1 declined at the expected rate for people of this age group. In people with HIV, the annual decline was almost 50% greater.
The rate of decline did not differ in over-50s between HIV-positive and HIV-negative people.
Detectable viral load made little difference to the rate of decline in people with HIV. Across the entire age range, current CD4 cell count did not affect the rate of FEV1 decline in people with HIV and did not differ from HIV-negative people.
Lowest-ever CD4 cell count did affect the rate of decline; people with nadir CD4 counts below 200 experienced more rapid decline in lung function than people with higher nadir CD4 counts. People with nadir CD4 counts above 200 did not experience faster declines in lung function than HIV-negative people.
The findings suggest that arresting damage to lung function in people with HIV needs to begin early, with smoking cessation a priority.