Formal education as an effect modifier of the relationship between Mini-Mental State Examination score and IADLs disability in the older population

The objective of this retrospective, case-series study was to examine the relationship between disability in Instrumental Activities of Daily Living (IADLs) and cognitive impairment measured by the Mini-Mental State Examination (MMSE), and how this relationship was influenced by different levels of formal education. The setting of the study was the Cognitive Disorders Center of the Local Sanitary Unit (USL) No. 4 in Prato (Italy). Independence in IADL was strongly related to MMSE scores. A score of less than 24 at the MMSE was predictive of disability in at least one IADL with 0.82 sensitivity and 0.73 specificity. However, when only people with a very low level of formal education were considered, the best threshold predicting IADL disability was 17 (sensitivity 0.76, specificity 0.75). Thus, scholastic achievement is an effect modifier of the relationship between cognitive status, as measured by the MMSE, and IADL disability. Subjects with low education level and poor performance at the MMSE are often independent in activities making demand on cognitive function, such as IADLs. These results suggest that a lower MMSE cut-off score should be considered when screening for cognitive impairment in these persons.