Childhood mental ability and late-onset dementia

• Main Author: McGurn, Brian
• Published: University of Edinburgh 2008
• Subjects: 610.21
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.666243

Studying late-life cognitive change requires a measure of cognitive ability in early life. The Scottish Mental Survey of 1932 gives a valid measure of childhood mental ability age 11 years, the Moray House Test (MHT). Cases with vascular dementia had a lower MHT score than controls (mean MHT in cases = 34.0, mean MHT in controls 41.5, p=0.02). This translates to an odds ratio of 0.68 (95% CI 0.50 – 0.94; p=0.021) for every 10 point increase in MHT. There was no relationship demonstrated between childhood mental ability and late-onset AD. This association between childhood mental ability and vascular dementia has not been described previously. The estimation of pre-morbid mental ability is often required to demonstrate the cognitive decline required to diagnose dementia. The neuropsychological test most frequently used is the National Adult Reading Test (NART). NART scores were compared in cases with dementia (n=45) to healthy volunteers (n=550). Cases with dementia scored lower on the NART in old age, but also scored lower on MHT age 11. After adjusting the NART score for MHT age 11, the dementia and non-dementia groups no longer differed on NART scores. Pearson correlations between NART and MHT (measured more than 60 years apart) were similar in the dementia group (r =.60) and the non-dementia group (r =.63). These results confirm that the NART is a valid test of pre-morbid mental ability even in the presence of mild-moderate dementia. Changes on the resting electrocardiograph (ECG) can be considered a marker of vascular disease. Cognitive test scores were compared in a group of people with and without ECG changes. There was no difference in MHT between the two groups. Men with left ventricular hypertrophy had lower MMSE. Both left ventricular hypertrophy and conduction defects are associated with reduced scores on verbal fluency in women. Overall, this thesis establishes that lower childhood mental ability is associated with higher risk of dementia. This occurs for vascular but not Alzheimer’s dementia.