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Table 2 Neuropsychiatric inventory measure of sleep disturbance (NPI)

From: APOE ε4, Alzheimer’s disease neuropathology and sleep disturbance, in individuals with and without dementia

Frequency score Severity score
1 Occasionally Less than once per week 1 Mild Night-time behaviours occur but they are not particularly disruptive
2 Often About once per week 2 Moderate Night-time behaviours occur and disturb the participant and the sleep of the caregiver, more than one type of night-time behaviour may be present
3 Frequently Several times per week but less than every day 3 Marked Night-time behaviours occur; several types of night-time behaviour may be present; the participant is very distressed during the night and the caregiver’s sleep is markedly disturbed
4 Very frequently Once or more per day