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

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.