Some Correlations in Geriatric Patients between EEG Parameters and Clinical Status as Evaluated Using the Observer-Rated SCAG Rating Scale

Abstract

In a retrospective analysis, correlations were sought between pretreatment electroencephalographic and clinical data obtained in 18 therapeutic studies conducted in elderly patients according to almost identical protocols. Power spectrum analysis was applied to the EEG tracings, while clinical status was observer-rated using the Sandoz clinical assessment – geriatric (SCAG) scale. The study population comprised a total of 286 patients between the ages of 51 and 97 years (median age 70 years), 162 of whom were male (median age 68 years) and 124 female (median age 73 years). A 2-week washout period and several ‘adaptation recordings’ preceded the pretreatment EEGs used in this analysis. These tracings were recorded under resting conditions between 8 and 10 a.m. and were followed by an assessment of clinical status. Spearman rank correlations with 4 EEG parameters – total slow waves, alpha and beta waves, and dominant alpha frequency – were computed for all 18 SCAG items and for Overall impression of patient’ as well as for 5 SCAG factors. All 96 – (19+5) × 4 – correlation coefficients were formally tested for statistical significance at the nominal level of α = 0.05. In this analysis, 9 of the 18 items, Overall impression’ and two of the factors (‘apathy’ and ‘somatic dysfunction’) showed nominally significant correlations with at least 1 of the 4 EEG variables. As expected, a positive correlation was found between percentage slow-wave activity and degree of clinical impairment. In addition correlations were identified between clinical data and alpha and beta activity. Limitations due to the retrospective nature of the study were as follows: most of the patients had been preselected with the aid of the 7-point SCAG rating scale and showed only moderate degrees of impairment (score of 3 or 4) for most items; consequently, there were few low or high scores (1–2 or 5–7). Moreover, the original studies were conducted by 12 different clinicians in 6 different European countries, while the computation of correlation was based on a single EEG lead (O2-Q; 5-min tracing recorded under resting conditions only). In view of this and of the wide range of additional information contained in the EEG, it is remarkable that nominally significant correlations were found between the EEG data and a relatively high proportion of the SCAG items. These correlations can also be seen as a contribution to the validation of the SCAG rating scale by an external criterion.