Frequency of incarceration associated with risk of poor HIV treatment adherence for injecting drug users

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Incarceration is associated with poor adherence to HIV therapy among injecting drug users, an international team of researchers report in the May 1st edition of the Journal of Infectious Diseases.

Just one instance of imprisonment increased the risk of sub-optimal adherence to antiretroviral treatment, and the more often a patient was incarcerated then the greater their risk of poor adherence.

“We observed a dose-dependent association between the cumulative burden of incarceration and ART [antiretroviral therapy] nonadherence,” comment the investigators, who believe their study “clearly indicates that increasing number of cycles of imprisonment, release and reincarceration is associated with poorer ART adherence in this population of IDUs [injecting drug users].”


person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

disease progression

The worsening of a disease.


An alternative term for ‘adherence’.




The prospect of survival and/or recovery from a disease as anticipated from the usual course of that disease or indicated by the characteristics of the patient.

Thanks to modern antiretroviral therapy, many HIV-positive individuals now have a near-normal prognosis. High levels of adherence are needed to achieve the best outcomes.

Good results have been seen in HIV-positive injecting drug users treated with antiretrovirals. However, some drug users have difficulty achieving the high levels of adherence necessary for optimal viral suppression.

Incarceration is common among drug users, and it has been estimated that approximately 10% of HIV-positive individuals are imprisoned each year in the US. Significantly for HIV treatment outcomes, some research had suggested that incarceration is associated with an increased risk of interrupting antiretroviral therapy.

Therefore, a team of Canadian and British investigators sought to estimate the frequency of imprisonment among HIV-positive drug users and the association between incarceration and sub-optimal adherence to antiretroviral therapy.

The study was conducted in Vancouver, British Columbia, and its population included 490 HIV-positive injecting drug users who were enrolled in the AIDS Care Cohort to Evaluate Exposure to Survival Services (ACCESS). Recruitment and follow-up took place between 1996 and 2008.

All the patients were taking antiretroviral therapy, and every six months they were interviewed about their experiences of incarceration.

Adherence was assessed using pharmacy refill records, and was defined as sub-optimal if below 95%. Incarceration was defined as spending at least one night in police custody or a prison of some kind.

The median duration of follow-up was a little under 29 months and the investigators had a total of 2220 person-years of follow-up available for analysis.

Over half (55%) of the patients were imprisoned at least once, and the overall incarceration rate was 52.5 per 100 person years. The median number of incarcerations per patient was three, and there were a total of 1156 incarceration episodes.

During the entire period of the study, the overall adherence rate was 61%, well below the target 95%. Of the 3731 six-month follow-up periods included in the investigators’ analysis, 36% were characterised by sub-optimal levels of adherence.

There was a robust association between experiencing incarceration and poor adherence to HIV therapy.

Compared to individuals with no history of incarceration, those imprisoned on one or two occasions were almost twice as likely to be non-adherent during subsequent follow-up (odds ratio [OR], 1.91; 95% CI, 1.35-2.72).

The risk of sub-optimal adherence increased to 2.85 (95% CI, 1.87-4.33) for patients incarcerated who had three to five experiences of incarceration, and an even higher risk of poor adherence was observed for individuals with five or more episodes of imprisonment (OR = 3.59; 95% CI, 2.12-6.09).

These results remained substantially unaltered when the investigators controlled for sex, cocaine use, engagement in methadone treatment programmes, duration of HIV therapy and viral load.

Modern combinations of antiretrovirals can achieve good results with adherence rates of approximately 85%. However, the investigators found that increased frequency of incarceration was still associated with a greater risk of treatment non-compliance using this definition of adherence.

“Because of the tight link between nonadherence and HIV disease progression, our findings have direct relevance to public health efforts to reduce AIDS-related morbidity and mortality and continued viral transmission,” comment the authors.

They conclude, “given the importance of correctional facilities in shaping the health of vulnerable HIV-positive individuals, our findings should spur efforts to reform the delivery of in-prison HIV care and ease transitions to noncorrectional environments.”


Milloy MJ et al. Dose-response effect of incarceration events on nonadherence to HIV antiretroviral therapy among injection drug users. J Infect Dis 203: 1215-21, 2011 (click here for the free abstract).