There were significant changes in health and lifestyle throughout the 20th century which may have changed temporal patterns of hearing impairment in adults. In this study, the authors aimed to assess the effect of birth cohort on the prevalence of hearing impairment in an adult population aged 45-94 years, using data collected between 1993 and 2008 from 3 cycles of the Epidemiology of Hearing Loss Study (n = 3,753; ages 48-92 years at baseline) and a sample of participants from the Beaver Dam Offspring Study (n = 2,173; ages > or =45 years). Hearing impairment was defined as a pure-tone average of thresholds at 0.5, 1, 2, and 4 kHz greater than 25-dB HL [hearing level]. Descriptive analysis, generalized additive models, and alternating logistic regression models were used to examine the birth cohort effect. Controlling for age, with every 5-year increase in birth year, the odds of having hearing impairment were 13% lower in men (odds ratio = 0.87, 95% confidence interval: 0.83, 0.92) and 6% lower in women (odds ratio = 0.94, 95% confidence interval: 0.89, 0.98). These results suggest that 1) older adults may be retaining good hearing longer than previous generations and 2) modifiable factors contribute to hearing impairment in adults.