The population-based Beaver Dam Eye Study was designed by Barbara E. K. Klein, MD, MPH, and colleagues to determine through long-term observation whether there were differences among age cohorts regarding rates of cataract prevalence and surgery, as well as type of cataract. Five thousand residents of Beaver Dam, Wisconsin were examined for the three most common forms of cataract-nuclear, cortical and posterior sub-capsular—at baseline in 1990 and five, 10 and 15 years later. Results were analyzed by age group and gender for this population, which was 99 percent white. The rates of all three cataracts increased with age for all cohorts and are described in the study in detail by age cohort and gender.
An interesting decline in prevalence of nuclear cataract—the type characterized by hardening of the center of the eye’s lens—was found when participants were considered in five-year age and birth cohorts (excluding the 75+ group, which had too few participants). Even after adjusting for expected higher prevalence at older ages, the study found that prevalence declined in each successive birth cohort. The authors suggested that this decline may be related to negative health habits shared by people in the older cohorts and to more positive health habits in the younger cohorts. The researchers write: “Possible protective exposures include a decrease in smoking and increase in exposure to healthy lifestyle habits.” Rates of cataract surgery also increased in the 15-year time period, as surgical techniques and outcomes improved significantly and more people elected cataract surgery at earlier points in the disease process.