Cognitive screening of nursing home residents: factor structures of the Mini-Mental State Examination.

Objective: To examine factor structures of the Mini-Mental State Examination, attempting first to replicate any of previously proposed 2-factor solutions; and to explore, secondly, the presence of clinically more differentiated and statistically stable factor structures representing common neurocognitive dimensions.

Design: Factor analytic investigation of descriptive dataset collected on nursing home residents. Two factor analyses were performed, one in which the number of factors was fixed at 2 in an effort to replicate previous studies, and one in which the number of factors to retain was determined by the scree test. Both factor analyses used established methods for judging the adequacy of the correlation matrix and the significance of factor loadings, and both applied principal components analysis for initial factor extraction and the equamax criterion for orthogonal rotation.

Setting: Seven nursing homes with a total of 894 beds.

Participants: 922 assessments on nursing home residents were performed, of which 892 were complete and entered into the factor analyses. The observation-to-variable ratio exceeded 81:1, assuring the statistical stability of factor solutions derived.

Measurement: The Mini-Mental State Examination, with standardization of words to be recalled and the inverted spelling of "world" as the mental reversal task.

Main Results: Two factor structures were derived. A 2-factor solution, explaining 36.5% of the variance and statistically and conceptually different from those obtained in previous studies, distinguished between Perceptual-Organizational and Psychomotor skills. A 4-factor solution, which explained 56.1% of the variance, included a factor named Executing Psychomotor Commands, while also further differentiating the perceptual-organizational processes into the factors of Memory, Concentration, and Language.

Conclusion: The 2-factor solution shows that, notwithstanding previous claims to the contrary, the MMSE can make stable and independent distinctions between psychomotor and perceptual-organizational processes. However, this solution is statistically and conceptually limited and, therefore, of limited clinical and scientific relevance. The 4-factor solution of the MMSE maps well onto commonly recognized dimensions of neurocognitive ability. It offers a stable, intuitively sound, and statistically supported framework for clinical differentiation of cognitive screening data into independent clinical dimensions of neurocognitive functioning. Thus, it offers clinicians and researchers a 4-dimensional framework for interpreting data obtained by means of the MMSE. Studies with other populations of cognitively impaired and intact elderly are recommended to validate and extend the present findings.