Decline in cognition from mid-life improves specificity of mini-mental state examination: diagnostic test accuracy in Caerphilly Prospective Study (CaPs)

Background: The merit of using baseline cognitive assessments in mid-life to help interpret cross-sectional cognitive tests scores in later life is uncertain. We evaluated how accuracy for diagnosing dementia is enhanced by comparing cross-sectional results to a midlife measure.

Method: Cohort study of 2,512 men with repeated measures of Mini Mental State Examination (MMSE) over approximately 10 years. Index test MMSE at threshold of 24 indicating normal, as a cross-sectional measure and in combination with decline in MMSE score from mid-life. Reference standard consensus clinical diagnosis of dementia by two clinicians according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).

Results: 1,150 men participated at phase 4 of whom 75 had dementia. A cross-sectional MMSE alone produced a sensitivity of 60% (50% to 70%) and specificity 95% (94% to 97%) with a threshold of ≥ 24 points indicating normal. For lower-scoring men in late life, with cross sectional scores of <22, combining
cross-sectional AND a three-point or more decline over time had a sensitivity of 52% (39% to 64%) and specificity 99% (99% to 100%). For higher-scoring men in later life, with cross sectional scores <26 combining cross-sectional OR decline of at least three points had a sensitivity of 98% (92% to 100%) and specificity 38% (32% to 44%).

Conclusion: It may be helpful in practice to formally evaluate cognition in mid-life as a baseline to compare with if problems develop in future, as this may enhance diagnostic accuracy and classification of people in later life.