Parity and the risk of incident dementia: a COSMIC study

Abstract

Aims To investigate the association between parity and the risk of incident dementia in women. Methods We pooled baseline and follow-up data for community-dwelling women aged 60 or older from six population-based, prospective cohort studies from four European and two Asian countries. We investigated the association between parity and incident dementia using Cox proportional hazards regression models adjusted for age, educational level, hypertension, diabetes mellitus and cohort, with additional analysis by dementia subtype (Alzheimer dementia (AD) and non-Alzheimer dementia (NAD)). Results Of 9756 women dementia-free at baseline, 7010 completed one or more follow-up assessments. The mean follow-up duration was 5.4 ± 3.1 years and dementia developed in 550 participants. The number of parities was associated with the risk of incident dementia (hazard ratio (HR) = 1.07, 95% confidence interval (CI) = 1.02–1.13). Grand multiparity (five or more parities) increased the risk of dementia by 30% compared to 1–4 parities (HR = 1.30, 95% CI = 1.02–1.67). The risk of NAD increased by 12% for every parity (HR = 1.12, 95% CI = 1.02–1.23) and by 60% for grand multiparity (HR = 1.60, 95% CI = 1.00–2.55), but the risk of AD was not significantly associated with parity. Conclusions Grand multiparity is a significant risk factor for dementia in women. This may have particularly important implications for women in low and middle-income countries where the fertility rate and prevalence of grand multiparity are high.

Endogenous and Exogenous Estrogen Exposures: How Women’s Reproductive Health Can Drive Brain Aging and Inform Alzheimer’s Prevention

“…However, while some studies indicate that having 1–3 children may provide protective effects against dementia ( Heys et al, 2011 ; Ning et al, 2020 ; Song et al, 2020 ), grand multiparity (5 or more pregnancies) may have detrimental effects instead ( Rasgon et al, 2005a ; Bae et al, 2020 ; Song et al, 2020 ; Figure 2E ).…”

“…Discrepancies among studies may be due to small sample sizes ( Corbo et al, 2007 ; Beeri et al, 2009 ), differences in cognitive assessments ( Ryan et al, 2009 ) or diagnostic criteria ( Ptok et al, 2002 ; Beeri et al, 2009 ; Bae et al, 2020 ), possible inclusion of non-biological children ( Bae et al, 2020 ), and different exposure variables including parity (parous vs. nulliparous) ( Ptok et al, 2002 ), gravidity ( Colucci et al, 2006 ; Fox et al, 2018 ), number of children ( Rasgon et al, 2005a ; Heys et al, 2011 ), number of living childbirths ( Bae et al, 2020 ; de Lange et al, 2020 ; Ning et al, 2020 ), or number of months spent pregnant ( Fox et al, 2018 ). Associations with cognition were more commonly observed when parity was defined as number of childbirths or time spent pregnant rather than as having vs. not having children.…”

Reproductive Factors and Risk of Dementia in Natural Postmenopausal Women: a Cross-sectional Study

“…Previous studies indicated that parous women had shorter reproductive periods and lower level of estradiol than nulliparous women, and thus greater parity could lead to an overall lower levels of lifetime estrogen exposure [36, 37]. These ndings had been proved in many studies [38][39][40][41]. Women with higher number of pregnancies had indirectly relate to higher estro-progestinic exposure.…”

The Mediating Role of SES on the Relationship between Pregnancy History and Later Life Cognition

“…13 Similar studies suggest that grand multiparity, defined as having 5 or more children, has a negative effect on cognition as measured by Mini-Mental State Examination (MMSE), Digit Symbol Substitution Test (DSST), and DSM-IV criteria for dementia diagnosis. 4,5,7,14 Alternatively, Lange et al 3 found that women with prior pregnancies had slower brain aging in striatal and limbic regions, with strongest associations in women with 5 or more pregnancies. 3 Other studies have similarly found better cognitive function or no difference in cognition when comparing women that report term pregnancies with those that report never being pregnant.…”

“…menarche, childbearing, menopause) and their relation to later life cognition have gained increasing attention in recent literature and might contribute to sex differences in ADRD risk. [3][4][5][6][7][8] Pregnancy results in a myriad of physiological changes that are known to impact brain health including fluctuation in hormone levels, neuroplasticity, immune function, and cardiac output. [9][10][11][12] However, the association between pregnancy and later life cognition is poorly understood.…”