UC Berkeley

Diarrhea remains a significant cause of morbidity and mortality worldwide, especially for children and persons with compromised immune status. This dissertation considers two key subpopulations that are higher risk for gastrointestinal illness due to immunocompromise, persons living with Human Immunodeficiency Virus (HIV), and older adults over 55 years of age. Three investigations with different methodologies (population survey, meta-analysis, and case-control study) on different aspects of diarrhea burden, risk patterns and etiology in these two populations are presented.

The pathogenesis of diarrhea is complex and associated with multiple etiologies including bacterial, parasitic and viral pathogens, adverse events from medications, tumors and underlying immune status. The relative contributions of these risk factors to the overall burden of diarrheal illness is unknown and may vary by geographic location, immune status and access to anti-retroviral medications. Gastrointestinal adverse events are the most frequently cited reason for discontinuation for highly active antiretroviral therapy (HAART) and significantly influence patient adherence. As treatment decisions are increasingly made with regard to tolerability, probability of adherence, and patient quality of life, the burden of diarrhea associated with various HAART regimens may be critical in determining an individual's optimal treatment course. A systematic review to estimate the rates of diarrhea among HIV-infected individuals associated with specific HAART regimens was conducted showing protease inhibitor containing regimens to confer the highest rates of diarrhea. Diarrhea presents a persistent challenge to those living with HIV under anti-retroviral treatment and varies by regimen composition. Additionally, a prospective case control study of acute, chronic and asymptomatic diarrhea was conducted among an urban HIV+ clinic cohort to evaluate the relative risk of diarrhea due to medication and infectious pathogens.

Lastly, a random digit dial serial cross-sectional survey among 2163 adults over 55 years of age was conducted in Sonoma County, California from September 2001 to September 2005 to estimate the prevalence of gastrointestinal illness. The average monthly prevalence of gastrointestinal illness (vomiting or diarrhea) was 7.34% (6.23, 8.63), corresponding to an incidence rate of 0.99 (95% CI: 0.84, 1.48) episodes per person per year. Of those reporting gastrointestinal illness, 30.0% experienced vomiting, 23.4% sought medical care, and 10.8% took antibiotics.