Abstract
Purpose: :
Birth cohort effects have been reported for the risk of age-related macular degeneration (AMD) but it is not known if this trend has continued for people born during the baby boom years (1946-64) in the U.S. The purpose of this paper was to determine if the birth cohort effect for AMD prevalence extends to more recent generations and evaluate the impact of potential risk factors on the magnitude of the effect.
Methods: :
Data from the Beaver Dam Offspring Study (BOSS) for participants 45 yrs of age or older at examination and data from the parental cohort (Beaver Dam Eye Study/Epidemiology of Hearing Loss Cohort; BDES/EHLS) were included. AMD was graded using digital (BOSS) and film-based images (BDES). The BOSS and BDES/EHLS included extensive questionnaire information about behaviors, environmental factors and medical history and measures of blood pressure, diabetes, cholesterol, etc. A total of 9930 observations for participants born between 1905 and 1962 were included in alternating logistic regression models which controlled for repeated measures and familial correlations.
Results: :
The prevalence of AMD declined with birth year (lower for recent generations; age and sex-adjusted OR=0.75 for 5 yrs, p<0.001). This birth cohort effect (OR=0.77, p<0.001) remained in multivariate models adjusting for factors independently associated with AMD (obesity, education, heavy drinking). Cigarette smoking was not significantly associated with AMD in these models. In a subset (n=7727 observations) with additional data about childhood exposures, the birth cohort effect remained with additional adjustments for sunlight exposure, parental home ownership, and method of transportation to school (OR=0.80 for 5 yrs, p<0.001).
Conclusions: :
Today’s aging baby boomers may be less likely to have AMD than previous generations. This rapid decline in AMD prevalence (68% lower each generation) suggests that modifiable factors play important roles in the etiology of AMD. Including other factors associated with AMD partially explained the birth cohort effect but suggests that childhood exposures may contribute to the risk of AMD. Longitudinal studies of exposures in childhood or early adult life and AMD incidence may identify new risk factors and pathways to improve eye health in adults.
Keywords: age-related macular degeneration • clinical (human) or epidemiologic studies: prevalence/incidence • clinical (human) or epidemiologic studies: risk factor assessment