The adverse effect of modifiable dementia risk factors on cognition amplify across the adult lifespan

Abstract

Background: Modifiable lifestyle behaviours can reduce dementia risk by 40%, but their prevalence and association with cognition throughout the adult lifespan is less well understood. Methods: Associations between eight modifiable risk factors for dementia (low education, hypertension, hearing loss, traumatic brain injury, alcohol or substance abuse, diabetes, smoking, and depression) and cognition were examined in an online sample (N = 22,117, aged 18-89). Findings: Older adults (ages 66-89) had more risk factors than middle-aged (ages 45-65) and younger adults (ages 18-44). Polynomial regression revealed each additional risk factor was associated with a drop in cognitive performance (equivalent to three years of aging), with a larger association as age increased. People with no risk factors in their forties to seventies showed similar cognitive performance to people ten or twenty years younger with many risk factors. Interpretation: Modifiable dementia risk factors may be more important than age in predicting cognitive performance.

Modifiable risk factors for dementia, and awareness of brain health behaviors: Results from the Five Lives Brain Health Ireland Survey (FLBHIS)

“…In this context, the current study aimed to explore exposure to and awareness of specific modifiable risk factors for dementia. As previous research has reported an unequal distribution of modifiable risk factors in the general population (Bobrow et al, 2021;LaPlume et al, 2022), we also aimed to investigate whether exposure to these risk factors is associated with demographic and socioeconomic factors, and to explore whether modifiable risk factor awareness varies between groups.…”

Sex differences and modifiable dementia risk factors synergistically influence memory over the adult lifespan

“…We use a lifespan sample, as emerging consensus recommends a life‐course perspective for modifiable risk factors, based on evidence that modifiable risk factors accumulate over life to influence likelihood of dementia later in life 17,18 . Similarly, the negative dose‐response association between combined modifiable risk factors and cognition increases over the adult lifespan 32 . A life‐course perspective is especially relevant to the interaction between sex and modifiable risk factors, as sex differences in risk‐factor prevalence vary with age (eg, diabetes and hypertension are more common in men in mid‐adulthood, but equal or more common in women after menopause or in older adulthood 25,37,38 ), as does the interaction between sex and individual risk factors on cognition 3,7,25 …”

“…Studies of combined factors show that each additional modifiable risk factor lowers cognitive performance 29–32 and episodic memory, 33 regardless of the type of risk factor (a dose‐response effect). A cumulative approach also accounts for overlapping effects among individual factors 17,18 .…”

“…17,18 Similarly, the negative dose-response association between combined modifiable risk factors and cognition increases over the adult lifespan. 32 A life-course perspective is especially relevant to the interaction between sex and modifiable risk factors, as sex differences in risk-factor prevalence vary with age (eg, diabetes and hypertension are more common in men in mid-adulthood, but equal or more common in women after menopause or in older adulthood 25,37,38 ), as does the interaction between sex and individual risk factors on cognition. 3,7,25 Our aims were to (1) characterize sex differences in the number and type of modifiable risk factors at different age periods and (2) test if sex, the number of modifiable risk factors, and cross-sectional age differences interact to influence cognitive abilities impacted in Alzheimer's disease (specifically, interference control, set shifting, working memory, and associative memory).…”

“…6 However, newer research increasingly recommends studying combined rather than individual risk-factor effects, based on findings that age-related disease works in a cumulative manner, such that each factor in the aggregate may be strongly associated with dementia even when some individual factors do not have a significant effect on cognitive decline. 29,30 Studies of combined factors show that each additional modifiable risk factor lowers cognitive performance [29][30][31][32] and episodic memory, 33 regardless of the type of risk factor (a dose-response effect). A cumulative approach also accounts for overlapping effects among individual factors.…”