Compared with HIV-positive people who do not inject drugs, injection drug users ran higher risks of liver or kidney disease in a 5,490-person U.S. comparison. But incidence of myocardial infarction (MI) and stroke were similar in the two groups, and people who injected drugs ran a non-significantly lower risk of non-AIDS cancers. The results were published in the June 1 issue of AIDS.
Non-AIDS comorbidities account for growing proportions of life-threatening illnesses in individuals taking antiretrovirals for HIV infection. People who acquire HIV through injection drug use (IDU) have a higher prevalence of classic risk factors for critical non-AIDS conditions; such risk factors include hepatitis C (HCV) coinfection, smoking and alcohol use. Because evidence on non-AIDS comorbidity incidence in drug injectors versus non-injectors remains scant, Johns Hopkins University researchers conducted this comparison.
The study included adults who entered the Johns Hopkins HIV Clinical Cohort between January 1995 and May 2014 and did not already have a confirmed diagnosis of end-stage renal disease (ESRD), end-stage liver disease (ESLD), MI or stroke. Participants could have a non-AIDS cancer diagnosis but would be analyzed only for cancers at a different site. The researchers used competing risk methods to compare cumulative incidence of the five non-AIDS diagnoses by age. This type of analysis accounts for death and adjusts for potential differences in loss to follow-up, which may be greater among drug injectors. Analyses did not adjust for hepatitis virus infection or illicit drug use because those factors probably mediate the association between IDU and comorbidities.
The 5490 study participants included 2028 drug injectors (37%) and 3462 non-IDU. Two-thirds of each group were men. The drug-injector group had an older median age at entry (41 versus 38 years), a higher proportion of blacks (83% versus 71%), and a higher proportion with HCV exposure (89% versus 24%) and a history of hazardous drinking (28% versus 15%). Similar proportions of the two groups had a baseline CD4 count ≥350 cells/mm3 (38% and 39%), a baseline viral load ≤400 copies/mL (20% and 22%) and exposure to antiretroviral therapy (54% and 55%).
Despite an approximately 50% higher death risk in drug injectors, analysis adjusted for baseline variables and loss to follow-up determined that at age 55 drug injectors had a higher risk of ESLD than non-IDU (6.8%, 95% confidence interval [CI] -1.9 to 15.5) and a higher risk of ESRD (11.1%, 95% CI 1.2 to 21.0). Stroke and MI risk at age 55 did not differ substantially between drug injectors and non-IDU, and risk of non-AIDS cancer was slightly lower in drug injectors (-4.9%, 95% CI -11.2 to 1.3).
Cause-specific adjusted hazard ratios (aHR) for non-AIDS comorbidities followed a similar pattern. Drug injectors had a tripled risk of ESLD (aHR 2.99, 95% CI 1.30 to 6.88) and more than a doubled risk of ESRD (aHR 2.29, 95% CI 1.43 to 3.69). Drug injectors had an elevated risk of stroke, but the association was not statistically significant (aHR 1.57, 95% CI 0.80 to 3.06). MI risk and non-AIDS cancer risk were nonsignificantly lower in drug injectors (aHR 0.82, 95% CI 0.49 to 1.39; and aHR 0.79, 95% CI 0.52 to 1.21).
The Johns Hopkins team concludes that not all non-AIDS comorbidities develop in drug injectors more often than in non-injectors. But higher risk of end-stage liver or renal disease in drug injectors "highlights the importance of recognition and management of markers of these comorbidities in early stages among [people who inject drugs]." The researchers note the importance of understanding the mediating impact of HCV infection on these findings since new anti-HCV therapies have transformed management of this infection. The authors caution that their results "should not be interpreted as the causal effect of continuous IDU" because some drug injectors stopped injecting during follow-up.