Role of functional performance in diagnosis of dementia in elderly people with low educational level living in Southern Italy

Abstract

Background and aims: Diagnosis of dementia is often difficult in subjects with low educational level. Our aim was to evaluate the role of functional performance and the possibility of preferring scores of activities of daily living (ADL) and instrumental activities of daily living (IADL) in screening elderly people for diagnosis of dementia in a rural population of Southern Italy with a very high percentage of non-educated subjects.

Methods: a random sample of 300 residents, out of 1089 subjects over 60 years of age living in San Marcellino (Caserta, Campania), received door-to-door visit for information about their medical history, with clinical evaluation of general geriatric conditions, including the cumulative illness rating scale (CIRS). Dementia was diagnosed if subjects had a Clinical Dementia Rating score (CDR) > or = 1 and according to the criteria of DSMIV, but not according to scores on the Mini Mental State Examination (MMSE), ADL and IADL. Two hundred and nineteen normal subjects (NS) and 75 patients with dementia (DP) were evaluated.

Results: in NS, their mean age- and education-corrected MMSE score was 22.15 (lower than the normal cut-off value of 23.8) and 12.60 in DP (p<0.0001). In NS, the mean ADL score was higher than in DP (5.53 vs 2.64, p<0.0001); only age was correlated with ADL scores (coeff=-0.44, t=-4.557, p<0.0001). Assuming age as covariate, ADL scores highly differentiated DP from NS (F(1, 289)=26.083, p<0.0001). In both sexes, mean IADL scores were higher in NS than in DP (4.46 vs 1.80 in men, p<0.0001; 6.85 vs 2.31 in women, p<0.0001). Age and education did not influence IADL scores in men, but age greatly affected performance in women. IADL scores clearly differentiated NS from DP. In NS, a positive correlation was evident between ADL and IADL scores (r=0.234, p<0.0005), but neither scores correlated with the MMSE scores, even when correlation was performed separately for men and women. In DP, a strong correlation was observed between ADL and IADL scores (r=0.709, p<0.0001) and significant correlations were also evident between the scores of MMSE and both ADL (r=0.492,p<0.0001) and IADL (r=0.398, p<0.0004).

Conclusions: in a rural community with a high prevalence of non-educated subjects, cognitive impairment is related to education, whereas independent functioning is limited mainly to age and not to cognition, if the latter remains (relatively) unimpaired. These results point to the importance of an "ecological" approach to the evaluation of elderly people, particularly those living in small rural communities, where education and the social environment may give rise to difficulties in diagnosis of dementia. The assessment of functional autonomy by ADL and IADL scales may be a better screening tool in diagnosing dementia than the MMSE scores.