Neuropsychological test norms controlled for physical health: does it matter?

The objective of the present study was to investigate the effects of physical health on neuropsychological test norms. Medical and neuropsychological data from 118 healthy volunteer controls, aged 26-91 years, were collected during five recruitment occasions. The examinations included a clinical investigation, brain neuroimaging, and a comprehensive neuropsychological test battery. Test-specific statistical regression-weights for age, education and gender were calculated to establish preliminary test norms. Hierarchical regression analyses demonstrated that control in addition for physical health moved best performance from age 60 to 65 for abstraction; replaced a plateau above age 70 for verbal fluency, with a continued rise in performance; eliminated significant negative influences of age on auditory learning, spatial reasoning and complex copying; reduced them on wordlist recall, psychomotor speed, visual scanning and mental shifting; and slightly reduced negative influences of low education on most verbal tests, several memory tests, and psychomotor speed, indicating rises in normative scores of up to 0.8 SD at age 80 and 0.4 SD at age 60. No differences were found at age 40. Although the sample size is not adequate to be used for normative data, the findings indicate that norms uncontrolled for health overestimate the negative influence of advanced age and low education, implying a risk of drawing false diagnostic conclusions.