Re: Bell‐McGinty et al. Standard measures of executive function in predicting instrumental activities of daily living in older adults

We were very interested by the paper by BellMcGinty et al. (2002) which shows a cross-sectional association between a lower performance on selected tests of executive function and IADL functioning. However, the authors are not completely right when they state that ‘this study is the only one, to date, to examine the differential contribution of specific, commonly used neuropsychological tests of executive function in predicting functional ability in a geriatric population’. Indeed, we conducted a survey in 1792 nondemented community dwellers aged 66 and over, included in the PAQUID (Personnes Agées QUID) study, to examine the relationships between performance on seven commonly used neuropsychological tests and selfreported performance on four selected Instrumental Activities of Daily Living (IADL) (Barberger-Gateau et al., 1999b). These four IADLs were selected because they were highly predictive of the onset of a dementia in the three to five subsequent years (BarbergerGateau et al., 1999a). Although these neuropsychological tests were not specific of executive functions, as most tests assess in fact several areas of cognitive functioning, most of them loaded on the first factor of a Principal Component Analysis which was interpreted as the most controlled aspect of the tests in a previous research (Fabrigoule et al., 1998). The four selected IADLs also loaded on this factor, indicating that impairment in these four activities was strongly associated with an impairment in controlled processes. Our analyses were adjusted for several confounders, including age, education, and visual and hearing impairments (Barberger-Gateau et al., 1999b). These results show that the early IADL limitations observed at the preclinical stage of dementia could be explained by a progressive impairment of controlled processes. Controlled processes are involved in tasks that require considerable attentional capacity. Executive dyscontrol (Royall, 1994) might be considered as the functional limitation resulting from impairment in controlled processes in the disablement process (Barberger-Gateau et al., 2002). Several other studies not cited by Bell-McGinty et al. have shown that executive dyscontrol is probably one of the major determinants of disability in dementia (Royall, 2000). An objective assessment of performance on everyday problems representing seven IADL domains in Alzheimer patients in the mild-tomoderate range of dementia severity also showed an association between their performance and measures of higher-order executive functioning (Willis et al., 1998). In other Alzheimer patients a relationship was found between low scores on executive skills tests and low performance in ADL and IADL rated on the Blessed Dementia Scale—Activities subscale, independent of MMS score (Chen et al., 1998). The paper by Bell-McGinty et al. (2002) adds to the growing body of evidence of the significant contribution of executive dysfunctioning to the prediction of disability in older subjects, beyond the cognitive functional limitations usually assessed in mental status tests, not only in normal subjects but also in Alzheimer patients.