High prevalence of emphysema in middle-aged HIV-positive smokers

HIV infection is associated with airway obstruction, French investigators report in AIDS. Middle-aged HIV-positive smokers were matched with HIV-negative smokers of the same sex and age. After controlling for potential confounders, the investigators found a significant association between HIV and airway obstruction, an association that persisted after controlling for history of previous serious lung disease. Smoking intensity was also a significant risk factor.

Lung function was measured using forced vital expiratory volume (FEV1) and forced vital capacity (FVC). FEV1 to FVC ratio was the primary outcome, and FEV1/FVC ratio below 0.70 and FEV1 below 80% was indicative of moderate to severe chronic obstructive pulmonary disease (COPD).

“We found that HIV infection was independently associated with lower FEV1/FVC ratios,” comment the authors. “HIV was also associated with an increased prevalence of airway obstruction.”

Glossary

matched

In a case-control study, a process to make the cases and the controls comparable with respect to extraneous factors. For example, each case is matched individually with a control subject on variables such as age, sex and HIV status. 

chronic obstructive pulmonary disease (COPD)

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease that causes obstructed airflow from the lungs. Symptoms include difficulty breathing, cough, mucus (sputum) production and wheezing. It is caused by long-term exposure to irritating gases or particulate matter, most often from tobacco smoking (active or passive).

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. Many BMI calculators can be found on the internet.

control group

A group of participants in a trial who receive standard treatment, or no treatment at all, rather than the experimental treatment which is being tested. Also known as a control arm.

nadir

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

Small airway disease with emphysema results in airway obstruction and possibly COPD. There is an elevated prevalence of this condition in people with HIV, possibly related to high rates of smoking and previous HIV-related lung disease.

French investigators wished to establish a clear understanding of the risk of airway obstruction in HIV-positive people, especially those with multiple risk factors for the condition (older age, smoking and previous immune suppression).

They designed a case-controlled study involving 351 HIV-positive people and 702 age- and sex-matched controls.

Key inclusion criteria were age 40 years or above, smoking history of 20 pack-years or more, nadir CD4 cell count below 350 cells/mm3, and current CD4 cell count above 100 cells/mm3. Recruitment was restricted to current smokers or people who quit smoking within the previous three years. Individuals were excluded if they had had a lung infection within the previous two months.

The median age was 50 years and 17% of participants were women. Participants had smoked for a median of 30 pack-years and 91% of people living with HIV were current smokers compared with 67% of the HIV-negative control group (p < 0.0001). The majority of HIV-positive people (89%) had an undetectable viral load and the median current CD4 cell count was 573 cells/mm3.

The FEV1/FVC ratio was significantly impaired in people with HIV compared to the controls (0.74 vs 0.78, p < 0.0001). Airway obstruction was diagnosed in almost a fifth (19%) of HIV-positive people compared to 9% of controls (p < 0.0001).

HIV was strongly associated with lower FEV1/FVC values (p = 0.001), as was increasing age (p < 0.0001), increased smoking intensity (p = 0.007) and hepatitis C virus co-infection (p = 0.008). In contrast, female sex (p = 0.028) and increased body mass index (BMI) (p < 0.0001) were both associated with higher FEV1/FVC values.

The association between HIV and lower FEV1/FVC persisted after exclusion of people with a history of tuberculosis or pneumocystis (p = 0.006).

“PLWHIV [people living with HIV] are at increased risk of bacterial infection, pneumocystosis, tuberculosis, conditions which have all been associated with airway obstruction or emphysema,” write the researchers. “However, other mechanisms may also be implicated, as suggested by the persisting association between HIV and FEV1/FVC ratio after excluding study participants with a history of tuberculosis or pneumocystis infection.”

Restricting analysis to people with a nadir CD4 cell count between 200-350 cells/mm3 found an association between HIV and impaired FEV1/FVC values of borderline significance.

After taking into account potential confounders, there was also a strong association between HIV and airway obstruction (OR = 1.72; 95% CI, 1.08-2.73). Other risk factors were increasing age (OR = 1.77 per 10 years; 95% CI, 1.28-2.43) and intensity of tobacco use (OR = 1.11 per 5 pack-years increase; 95% CI, 1.03-1.20).

“Our study found a higher prevalence of measured airway obstruction in PLWHIV with a history of important immunodeficiency than in age and sex-matched control group smokers 40 years of age or more,” conclude the investigators.

References

Matkinson A et al. HIV is associated with airway obstruction: a matched controlled study. AIDS, 32: 227-32, 2017.