Trends and causes of hospitalizations among HIV-infected persons during the late HAART era: what is the impact of CD4 counts and HAART use?
BACKGROUND
Declining rates of hospitalizations occurred shortly after the availability of highly active antiretroviral therapy (HAART). However, trends in the late HAART era are less defined, and data on the impact of CD4 counts and HAART use on hospitalizations are needed.


METHODS
We evaluated hospitalization rates from 1999 to 2007 among HIV-infected persons enrolled in a large US military cohort. Poisson regression was used to compare hospitalization rates per year and to examine factors associated with hospitalization.


RESULTS
Of the 2429 participants, 822 (34%) were hospitalized at least once with 1770 separate hospital admissions. The rate of hospitalizations (137 per 1000 person-years) was constant over the study period [relative rate (RR) 1.00 per year change, 95% confidence interval: 0.98 to 1.02]. The hospitalization rates due to skin infections (RR: 1.50, P = 0.02), methicillin-resistant staphylococcus aureus (RR: 3.19, P = 0.03), liver disease (RR: 1.71, P = 0.04), and surgery (RR: 1.17, P = 0.04) significantly increased over time, whereas psychological causes (RR: 0.60, P < 0.01) and trauma (RR: 0.54, P < 0.01) decreased. In the multivariate model, higher nadir CD4 (RR: 0.92 per 50 cells, P < 0.01) and higher proximal CD4 counts (RR of 0.71 for 350-499 vs. <350 cells/mm(3) and RR 0.67 for > or = 500 vs. 350 cells/mm(3), both P < 0.01) were associated with lower risk of hospitalization. Risk of hospitalization was constant for proximal CD4 levels above 350 (RR: 0.94 P = 0.51, CD4 > or = 500 vs. 350-499). HAART was associated with a reduced risk of hospitalization among those with a CD4 <350 (RR: 0.72, P = 0.02) but had smaller estimated and nonsignificant effects at higher CD4 levels (RR: 0.81, P = 0.33 and 1.06, P = 0.71 for CD4 350-499 and > or = 500, respectively).


CONCLUSIONS
Hospitalizations continue to occur at high rates among HIV-infected persons with increasing rates for skin infections, methicillin-resistant staphylococcus aureus, liver disease, and surgeries. Factors associated with a reduced risk of hospitalization include CD4 counts >350 cells per cubic millimeter and HAART use among patients with a CD4 count <350 cells per cubic millimeter.