The Versatility of Epidemiology: Association of Chronic Diseases to Age-Related Hearing Loss and the Risk of Cancer Within a Community Exposed to Gasoline

This dissertation demonstrates the versatility of epidemiology in public health research. The association between hearing sensitivity and diabetes, cardiovascular disease (CVD), and their risk factors was examined in a population of 2,049 adults within the Health, Aging, and Body Composition Study (mean age 77.5 ± 2.8 years; 37% black). CVD and diabetes may contribute to age-related hearing loss by affecting blood flow within the inner ear via macro- and micro-vascular changes. Clinical CVD was not associated with hearing sensitivity however; subclinical CVD measures were moderately associated with poorer auditory function in females. After controlling for age, race, and site, CVD risk factors positively associated with worse mid-frequency hearing thresholds in males were weight, insulin, glucose, triglycerides, and smoking and in females were heart rate and glucose. Risk factors associated with worse high frequency thresholds were weight, insulin, triglycerides, and smoking in males and heart rate, glucose, and smoking in females. Diabetes was associated with mid-frequency hearing loss upon adjustment for common hearing loss risk factors (OR=1.60; 95%CI: 1.26-2.02). The metabolic syndrome was associated with mid-frequency hearing loss in whites prior to excluding diabetics. These results suggest that diabetes, in conjunction with CVD, contributes to age-related hearing loss, particularly strial presbycusis, and independent of common hearing loss risk factors. Given the high prevalence of hearing impairment among older adults, the identification of potentially modifiable risk factors for age-related hearing loss is of public health significance. Epidemiology can also be utilized in more applied settings. A retrospective cohort study was conducted to determine if residents affected by an underground gasoline spill in Hazle Township/Hazleton, Pennsylvania were at increased risk for cancer from 1990-2000. A total of 663 individuals representing 275 households comprised the study population. Age-adjusted standard incidence ratios (SIRs) were calculated using Pennsylvania rates to determine expected numbers. The age-adjusted leukemia SIR for the gasoline affected area was 4.40 (95%CI: 1.09-10.24). These results suggest a possible association between chronic low-level benzene exposure and increased risk for leukemia in the residents living near the spill site. This project directly impacted the public health of residents and also demonstrated the importance of collaboration and surveillance