Background:  HIV is now a complex chronic disease in which the management of common co-morbid behaviors and conditions is of increasing importance. We sought to characterize the prevalence of co-morbidity in 2 samples of HIV-infected individuals.

Methods:  We identified individuals infected with HIV under care in the California State Medicaid (Medi-Cal) program and the United States Veterans Healthcare System (VA) from October 1, 1997 to December 31, 2003. Using data from the VA national electronic medical record and Medi-Cal claims combined with California hospital discharge abstracts, we identified and compared the prevalence of 20 co-morbid conditions and 12 AIDS-defining conditions for these individuals. Using a validated method of identifying comorbid events based upon International Classification of Diseases, Ninth Revision (ICD-9) codes, clinical events occurring within 12 months before and 6 months after presentation for HIV care were considered prevalent cases. We used a weighted average of the samples to determine the top 10 conditions. We compared the unadjusted prevalence in the 2 samples using χ² tests.

Results:  We identified 33,037 Medi-Cal recipients and 16,573 veterans in care for HIV during this period. Veterans were on average 10 years older, more likely to be male, more likely to be black, and less likely to have AIDS than those in the Medi-Cal sample (p <0.001). In both samples, co-morbid diseases were more common than AIDS-defining conditions. The 10 most prevalent co-morbid conditions were (Medi-Cal, VA):  alcohol abuse (18%, 20%); hypertension (13%, 23%); drug abuse or dependence (10%, 22%); pulmonary disease (12%, 9%); renal failure (9%, 7%); hepatitis C (5%, 14%); diabetes (6%, 9%); major depression (5%, 7%); schizophrenia (5%, 5%); and coronary artery disease (4%, 6%). Prevalence varied by age, race, and whether or not the subject had developed AIDS (p <0.001). Substance abuse and related conditions, such as hepatitis C, were more prevalent in younger patients while co-morbid medical conditions—such as diabetes, hypertension, and coronary artery disease—were more prevalent in older patients.

Conclusions:  Substance abuse, in particular alcohol abuse or dependence, is the most common co-morbidity among those with HIV infection, and exceptionally common in the younger population. Other co-morbid conditions are also common. Now that treated HIV infection enjoys an extended life expectancy, the management of co-morbidity is of increasing importance.