Birth weight and cognitive performance in older women: the Rancho Bernardo study

Low birth weight is associated with poorer cognitive function from infancy through early adulthood, but little is known about low birth weight and cognitive performance in the elderly. This study examines the association of birth weight with cognitive function in community-dwelling older women. Participants were 292 community-dwelling women aged 55-89 (median = 71 years) who attended a 1988-91 clinic visit when cognitive function was assessed, and responded to a 1991 mailed questionnaire assessing birth weight. All analyses were adjusted for age and education. Birth weight ranged from 2 to 12 pounds (lbs; mean = 7.4 +/- 1.9). When birth weight was categorized into tertiles (2-6.9 lbs, 7-8 lbs, and 8.1-12.4 lbs), women in the lowest tertile had significantly lower ("poorer") scores on Serial 7's, a test of concentration and calculation (p < 0.05). Other birth weight categorizations (lowest quartile or quintile, or birth weight <5.5 lbs vs. 5.6-8.9 lbs and >or=9 lbs) did not improve the prediction of poor performance on Serial 7's. Birth weight as a continuous variable was significantly and positively associated with Serial 7's test scores (p = 0.04). Results suggest that small decrements in cognitive function tasks involving calculation may persist throughout life in women who were of relatively low birth weight. Although this association could be spurious, it deserves further evaluation.