Abstract
The presence of an apolipoprotein E (APOE) ε4 allele, lower physical fitness, smoking, and lower serum vitamin B-12 have been reported as contributing to poorer cognitive function in LBC1921 at age 79, after adjusting for childhood intelligence. Because incident dementia was not previously ascertained within LBC1921, it is possible that preclinical or unrecognized cases at age 79 influenced findings. Dementia cases arising over approximately 16 years of follow-up were determined by a consensus using evidence from electronic medical records, death certificates, and clinical reviews. The analyses from the original reports were repeated after the exclusion of those who had developed dementia. In a subsequent set of analyses, the authors considered the potential impact of terminal decline, excluding those participants who died within 4 years of baseline testing. Positive APOE ε4 status was found to be associated with poorer Logical Memory (Wechsler, 1987) at age 79 (F(1, 355) = 8.16, p = .005, ηp2 = 0.022; n = 359) and lower Moray House Test (Scottish Council for Research in Education, 1933) score at age 79 (F(1, 357) = 4.27, p = .04, ηp2 = 0.012; n = 363). Lower age 79 IQ was associated with smoking (F(2, 360) = 3.67, p = .026, ηp2 = 0.020; n = 367), lower vitamin B-12 (Sβ = 0.11, p = .014; n = 367), and poorer physical fitness (Sβ = 0.21, p < .001; n = 359). Only the relationship with physical fitness remained significant after excluding those who died within 4 years of baseline (Sβ = 0.203, p < .001; n = 310). Unrecognized dementia had little or no effect on determinants of lifetime cognitive ageing in LBC1921. Terminal decline may have accounted for the associations with age 11 to age 79 cognitive change.
Highlights
The presence of an apolipoprotein E (APOE) ε4 allele, lower physical fitness, smoking, and lower serum vitamin B-12 have been reported as contributing to poorer cognitive function in LBC1921 at age 79, after adjusting for childhood intelligence
We considered repeating our analyses using a stricter Mini-Mental State Examination (MMSE) cut-off to identify those who might subsequently develop dementia, but a receiver operator characteristic (ROC) curve determined that the discriminating power of the MMSE was insufficient to determine future dementia outcomes in this cohort, and it was little better than random allocation
Terminal decline analyses resultsg participants: 2 participants had reported a diagnosis of dementia at Wave 1; 9 participants scored less than 24 on the MMSE at Wave 1; 2 participants were missing MMSE scores at baseline; and there were 117 participants for whom we had ascertained a diagnosis of dementia in about 16 years of follow up, to age 95 years
Summary
The presence of an apolipoprotein E (APOE) ε4 allele, lower physical fitness, smoking, and lower serum vitamin B-12 have been reported as contributing to poorer cognitive function in LBC1921 at age 79, after adjusting for childhood intelligence. With an improved understanding of normal cognitive ageing it might be possible to distinguish it more clearly from pathological ageing. This will become increasingly important as the diagnosis of neurodegenerative conditions shifts earlier and earlier to prodromal and preclinical states. Alzheimer Scotland Dementia Research Centre and Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
