The effect of birthweight and gestational age on cognitive function in midlife: the Bogalusa heart study.

BACKGROUND

Although the relationships between birthweight, gestational age (GA), and cognitive function (CF) before midlife have been demonstrated, the relationships after midlife and potential racial disparities remain inconclusive. This study examined the association between birthweight, GA, and midlife CF stratified by race.

METHOD

1,032 subjects from the Bogalusa Heart Study (67% Whites, 33% Blacks, mean age 48.1 ± 5.3 years) were studied. Cognition was assessed with tests measuring verbal episodic memory, working memory, attention, graphomotor information processing speed, and global CF. Each test was standardized by sex and age, then averaged. The global CF was computed by averaging all cognitive test scores. Standardized scores from the Wide Range Achievement Test-IV (WRAT- IV)-Reading subtest and the Wechsler Adult Intelligence Scale- IV (WAIS-IV)-Vocabulary subtest measured achieved education. Multivariate linear regression was used to estimate the association.

RESULTS

A 100-gram increase in birthweight was associated with an increase of 0.007 standardized units in global CF (SE: 0.003; p = 0.016), 0.007 in working memory (SE: 0.003; p = 0.041), and 0.012 in graphomotor processing speed (SE: 0.004; p = 0.010). Stratified by race, the associations between birthweight and global CF and CF subdomains were not statistically significant in either race, likely due to reduced power, as the estimates in both races showed similar effect sizes to those in the total sample. No differences were observed in CF subdomains among small for GA, appropriate for GA, and large for GA groups. GA, analyzed as a continuous variable, was not associated with CF. However, in preterm births, it was associated with better global CF, working memory, and graphomotor information processing speed, while there was no association in term-born births.

CONCLUSIONS

The impact of birthweight on the global CF remained in middle age, while the impact of birthweight adjusted for GA did not. GA as a continuous variable was not associated with CF, except in preterm individuals, where it was associated with better CF. These results suggest that birthweight may influence CF in midlife, and GA may play a role, particularly in those born preterm.