Women using cocaine, heroin or methadone or injecting any drugs had 65% more AIDS-defining illnesses over a five-year period, according to a large prospective study of 1148 women in seven HIV clinics in five US states published in the November 1st edition of the Journal of Acquired Immune Deficiency Syndromes.
However it found no significant association between drug use and CD4 percentage, HIV viral load or mortality, and the investigators conclude that use of these drugs has no direct effect on the natural history of HIV.
The researchers said the design of their study was prompted by three considerations:
- While in vitro and animal studies have shown decreases in immune function and increases in HIV expression after exposure to ‘hard’ drugs, clinical studies have shown either no association or a small positive effect on immune function.
- Few studies of the relationship between drug use and health outcomes have been prospective, following both drug use and health over a period of time.
- Most former studies have compared intravenous drug users with gay men, groups demographically very different. The investigators compared health in drug-using and non-drug-using women who were similar in most other ways.
The present study was a substudy within the Women and Infant Transmission Study, a prospective, multicentre study of the natural history of HIV infection among pregnant women and their infants.
Subjects were recruited between December 1989 and December 1995 and then followed for a median time of 21.3 months, and a maximum of five years.
Eligible women were enrolled during pregnancy or around the time they gave birth and study visits (when practicable) were scheduled at five, three and one months before birth, then at two months after birth, twice-yearly till the child was three, then four and five years after birth.
Urine specimens to determine drug use were collected from the women at intake, during labour, and six months after giving birth. Thereafter women were asked at each visit if they had used cocaine or opiates or injected any drug over the previous year. Urine samples had an 80 to 90% concordance with the women’s self-reported drug use.
Investigators used CD4 percentage rather than absolute CD4 cell count as a measure of immune function because pregnancy, by increasing plasma volume, can dilute CD4 cell counts.
The 535 drug-using and 613 non-drug using women were broadly comparable. The group as a whole were 45% African-American, 36% Latina, and 15% white.
The drug users tended to be older. The only other significant differences were that drug users were much more likely to smoke while pregnant (75% vs. 29%) and to drink alcohol (63% vs. 32%). While 47% of the women reported drug use at any time during the study, only 26% reported it at every visit.
No association was observed between drug use and CD4 percentage or viral load over the five years of the study.
All cause mortality was 3% in drug users and 5% in non-drug users by the median follow-up time of 21 months, and 8% and 12% respectively after five years, but this was not significant. The only significant factor affecting death rates was use of highly active antiretroviral therapy (HAART), which reduced mortality by 80%.
However drug use was a significant predictor of the development of AIDS-defining illnesses, with a 65% greater risk in drug users. This was not apparent in women who were only followed as far as the median time of 21 months, where 8% of both groups had had an AIDS-defining illness, but by year five 20% of drug users had had an AIDS-defining illness vs. 12% of non-drug users.
The most common AIDS-defining illnesses were herpes infections, pneumonias of various types and tuberculosis (TB). Pneumonia and TB were significantly more common among drug users.
The investigators comment that these illnesses are common in drug users in general and often seen in HIV-positive people at relatively high CD4 counts. They may have therefore more to do with exposure to pathogens via drug use than with direct damage to immune function by drugs.
Thorpe LE et al. Effect of hard-drug use on CD4 cell percentage, HIV RNA level, and progression to AIDS-defining class C events among HIV-infected women. J Acquir Immune Defic Syndr 37:1423-1430, 2004.