Does incipient dementia explain normal cognitive decline determinants? Lothian birth cohort 1921

Area of Science:

• Neuroscience
• Gerontology
• Cognitive Psychology

Background:

• Previous research identified apolipoprotein E (APOE) ε4 allele, low physical fitness, smoking, and low vitamin B-12 as factors linked to poorer cognitive function at age 79.
• The influence of unrecognized dementia or terminal decline on these associations was not previously assessed in the LBC1921 cohort.

Purpose of the Study:

• To re-evaluate the determinants of cognitive function at age 79 in the LBC1921 cohort.
• To investigate the impact of incident dementia and terminal decline on the relationship between various factors and cognitive aging.

Main Methods:

• Cognitive function at age 79 was assessed using Logical Memory and the Moray House Test.
• Dementia cases were identified over a 16-year follow-up period using medical records and clinical reviews.
• Analyses were repeated excluding individuals with dementia and, subsequently, those who died within 4 years of baseline testing to account for terminal decline.

Main Results:

• Positive APOE ε4 status was associated with poorer Logical Memory and lower Moray House Test scores at age 79.
• Lower cognitive function at age 79 was linked to smoking, lower vitamin B-12, and poorer physical fitness.
• Only the association between physical fitness and cognitive function remained significant after excluding participants who died within 4 years of baseline, suggesting physical fitness is a robust predictor of cognitive aging.

Conclusions:

• Unrecognized dementia had minimal impact on the identified determinants of cognitive aging in the LBC1921 cohort.
• Terminal decline may explain some associations between early-life factors and cognitive changes observed over time.
• Physical fitness emerges as a critical, enduring factor influencing cognitive function in older adults, independent of preclinical dementia or terminal decline.