Parity is associated with cognitive function and brain age in both females and males

Abstract

previous studies of the association between parity and long-term cognitive changes have primarily focused on women and have shown conflicting results. We investigated this association by analyzing data collected on 303,196 subjects from the UK Biobank. We found that in both females and males, having offspring was associated with a faster response time and fewer mistakes made in the visual memory task. Subjects with two or three children had the largest differences relative to those who were childless, with greater effects observed in men. We further analyzed the association between parity and relative brain age (n = 13,584), a brain image-based biomarker indicating how old one's brain structure appears relative to peers. We found that in both sexes, subjects with two or three offspring had significantly reduced brain age compared to those without offspring, corroborating our cognitive function results. Our findings suggest that lifestyle factors accompanying having offspring, rather than the physical process of pregnancy experienced only by females, contribute to these associations and underscore the importance of studying such factors, particularly in the context of sex. Pregnancy involves dramatic hormonal and physiological changes. In part due to these large changes, the effect of pregnancy on cognitive and cardiovascular health has been studied 1,2. Declined cognitive function was observed during pregnancy 1,2. Researchers have also hypothesized that hormonal changes, which occur both during and after pregnancy, drive the association between parity (number of offspring) and cognitive function in later life. Multiple studies have investigated this association in females, though different conclusions have been found. Some studies found that parity was associated with better episodic memory and had a protective effect against Alzheimer's disease (AD) 3,4. Contrarily, parity has been associated with poor word recall score, Mini Mental State Exam score, and AD neural pathology 5,6. A recent study of approximately 10,000 male and female subjects found an association between the number of offspring and cognitive function in later life in both sexes, including memory and executive function, and suggested that socioeconomic status largely accounted for the association 7. In addition to the association between cognitive function and parity, the association between brain structural change and parity has been studied previously. Hoekzema et al. reported that the volume of certain gray matter regions was reduced during pregnancy and the reductions did not recover for at least 2 years post partum 2 , while others reported that the gray matter restoration process was evident within the first few months postpartum 8,9. Most studies on the association between brain structure and parity had a relatively small sample size (n < 100) and less than three years of postpartum follow-up 2,8,9. To date, it is still unclear if there are any long-term effects of parity on brain structure in the mid-to-old age population. We therefore so...

Relationship between parenthood and cortical thickness in late adulthood

“…This evidence of structural neuroprotection of parenthood has also been found in males [15]. In addition, middle-aged parents in the UK Biobank have faster response times and fewer errors on visual memory tasks than childless men and women [15].…”

Neuroprotective effects of motherhood on brain function in late-life: a resting state fMRI study

“…That is, parents showed "younger-looking" brains with increasing number of children, suggesting a neuroprotective effect of parenthood on brain-age. In addition, middle-aged parents have faster response times and fewer errors on visual memory tasks than childless men and women (Ning et al, 2020). In healthy older adults aged over 70-years, we reported that cortical thickness differs between parents and non-parents of both sexes (Orchard et al, 2020).…”

“…Taken together, current evidence is indicative of a life-long effect of parenthood on the human brain, which, at least in mothers, may be neuroprotective in ageing (de Lange et al, 2019;Ning et al, 2020;Orchard et al, 2020).…”

“…Notably, all existing studies of the influence of parenthood on the late life brain are limited by the sparse information on parenting in their sample (de Lange et al, 2019;Ning et al, 2020;Orchard et al, 2020). This limitation reflects the fact that existing studies have reported the effects of parenthood on brain structure and function using large datasets acquired for other purposes (here, to examine the effects of aspirin exposure on brain structure; de Lange et al 2019and Ning et al (2020) used data from the UK BioBank). Furthermore, it is important to note that reproductive experience is related to other traits which impact brain health in human ageing, including exposure to sex steroid hormones.…”

“…All edges related to motherhood are negatively weighted, therefore decreasing connectivity between networks (off-diagonal) indicates increased network segregation with increasing number of children mothered. Previous studies have reported neuroprotective effects of parenthood on brain structure later in life in mothers (de Lange et al, 2019;Ning et al, 2020;Orchard et al, 2020), and fathers (Ning et al, 2020 ageing effects, rather, that patterns of age-related changes in the brain are less evident in women with more children than those with fewer children. This is consistent with previous results suggesting mothers show "younger-looking" brains (e.g., de Lange et al, 2019).…”