BACKGROUND AND OBJECTIVES
Pregnancy outcomes such as low birth weight (LBW) delivery may reflect vascular or metabolic dysfunction in mothers and presage future cognitive impairment and dementia. However, the evidence is currently limited. Our objective was to examine the extent to which a lifetime history of LBW delivery was associated with cognitive function in parous middle-aged women.
METHODS
We studied participants from the Nurses' Health Study II, an ongoing longitudinal cohort of female nurses enrolled in 1989. In 2009, participants completed a reproductive history questionnaire. Participants who completed at least one of 2 post-traumatic stress disorder questionnaires were invited to participate in a cognition substudy with 2 waves of baseline data collection (2014 or 2018). We restricted the analysis to participants with one valid cognitive assessment who reported ≥1 birth at 18 years and older. We defined LBW delivery history as having delivered offspring with a birth weight <2,500 g (<5.5 lbs) in any pregnancy. The outcome was a single assessment of cognitive function evaluated with the self-administered Cogstate Brief Battery. The battery comprises 4 tasks, which we used to create 2 composite z-scores measuring psychomotor speed/attention and learning/working memory (higher z-scores = better cognitive function). We used multivariable linear regression models.
RESULTS
The analysis included 15,323 participants with a mean age of 62 (standard deviation: 4.9 years) at cognitive assessment. Among them, 1,224 (8%) had a history of LBW delivery. After adjusting for age at cognitive assessment, race, and ethnicity, participants' education, wave of baseline cognitive assessment, socioeconomic status, and prepregnancy characteristics, women with a history of LBW delivery had lower z-scores in the psychomotor speed/attention (β, -0.06; 95% CI -0.12 to -0.01) and learning/working memory (β, -0.05; 95% CI -0.09 to -0.01) composites than parous women without a history of LBW delivery. We observed a gradient of lower z-scores with an increasing number of LBW deliveries.
DISCUSSION
History of LBW delivery may be marker of future poorer cognition. If confirmed, our findings support future investigations into the value of early preventive efforts targeting women with a history of LBW delivery to reduce the burden of cognitive impairment in women.