Cut-off scores in MMSE: a moving target?

Background: Cognitive tests are known to be influenced by language, culture and education. In addition, there may be an impact of 'epoch' in cognition, because there is secular increase in scores of IQ tests in children. If we assume this is a long lasting process, then it should persist later in life. Methods: To test this hypothesis, we compared the performance of two cohorts of individuals (>= 50 years of age), evaluated 20 years apart using the Mini-Mental State Examination (MMSE). Results: Study population included 135 participants in 1988 and 411 in 2008. MMSE scores were higher in 2008 than in 1988 for literacy x age-matched subgroups, the difference being significant for participants with lower literacy. Score variance was explained by literacy (beta = 0.479, t = 14.598, P = 0.00), epoch (beta = 0.34, t = 10.33, P = 0.00) and age (beta = -0.142, t = -4.184, P = 0.00). Conclusion: The present results are in accordance with a lifelong secular improvement in cognitive performance. The operational cut-off values may change with time, which may have clinical impact in the diagnosis of disorders like mild cognitive impairment or dementia.