Relation between size at birth and risk of age-related macular degeneration.

PURPOSE To determine whether poor fetal growth, as determined by size at birth, is associated with increased risk of age-related macular degeneration. METHODS A total of 660 men and women born in Sheffield, United Kingdom, between 1922 and 1930 and whose size at birth was available were traced and invited to take part in the study. Of these, 392 attended for ophthalmic examination. Age-related macular degeneration in these volunteers was determined by the Wisconsin Age-Related Maculopathy Grading System. RESULTS The mean birth weight of subjects with macular degeneration (early or late) was heavier than that of those without (7.6 lb vs. 7.3 lb, respectively; P = 0.03). After adjustment for age, gender, and risk factors for macular degeneration, a significantly increased risk of macular degeneration was found in subjects with higher birth weight (odds ratio [OR] 1.5, 95% confidence interval [CI] 1.1-2.0 for each SD [1 lb, 5 oz] increase in birth weight). Other parameters describing size at birth showed a weaker relation or no relation with macular degeneration, but one of the measures of fetal proportion (head circumference-to-birth weight ratio) was significantly associated with risk of macular degeneration. Subjects with macular degeneration had a significantly lower head circumference-to-birth weight ratio than did those without (11.2 vs. 12.0 respectively, P = 0.01). CONCLUSIONS The finding that age-related macular degeneration was associated with increased rather than decreased birth weight was unexpected. Failure of the developing fetus's normal brain-sparing mechanism is a possible explanation for our finding of a lower head circumference-to-birth weight ratio among subjects with macular degeneration.