Assessing the impact of neuropsychiatric symptoms in Alzheimer's disease: the Neuropsychiatric Inventory Caregiver Distress Scale.

OBJECTIVES

To develop an adjunct scale to the Neuropsychiatric Inventory (NPI) for assessing the impact of neuropsychiatric symptoms in Alzheimer's disease (AD) patients on caregiver distress.

DESIGN

Cross-sectional descriptive and correlational study.

SETTING

University out-patient memory disorders clinics.

PARTICIPANTS

Eighty-five AD subjects and their caregivers (54 spouses, 31 children).

MEASUREMENTS

The NPI and NPI Caregiver Distress Scale (NPI-D) were used to assess neuropsychiatric symptoms in AD patients and related caregiver distress, respectively. Criterion validity of the NPI-D was examined (N = 69) by comparison with an abridged version of the Relatives' Stress Scale (RSS'), a general measure of caregiver stress, using item clusters that had previously been correlated to behavioral disturbances in demented patients. Test-retest (n = 20) and inter-rater reliability (n = 16) of the NPI-D were also assessed.

RESULTS

Test-retest and interrater reliability of the NPI-D were both adequate. Overall, caregiver NPI-D distress ratings were correlated significantly with the RSS' (r = .60, P < .001). RSS' ratings correlated strongly with NPI scores (r = .64, P < .001), even after controlling for degree of cognitive impairment based on the Mini-Mental State Exam (MMSE) score (r = .61). MMSE scores showed a moderate correlation to RSS' ratings (-.30, P = .02), but this association was markedly attenuated when controlling for the degree of neuropsychiatric disturbance based on the NPI score (r = -. 14). NPI-D ratings for 9 of 10 NPI symptom domains correlated most strongly with either NPI symptom severity or total (frequency x severity) scores. Agitation, dysphoria, irritability, delusions, and apathy were the symptoms most often reported to be severely distressing to caregivers.

CONCLUSIONS

The NPI-D provides a reliable and valid measure of subjective caregiver distress in relation to neuropsychiatric symptoms measured by the NPI. Neuropsychiatric alterations are more strongly associated than cognitive symptoms to caregiver distress. The NPI-D may be useful in both clinical and research settings for assessing the contribution to caregiver distress of neuropsychiatric symptoms in AD patients.