Prevention of depression and sleep disturbances in elderly with memory-problems by activation of the biological clock with light

Depression, measured with the Geriatric Depression Scale (GDS), using the complete 30 items version. The GDS is a list of statements and patients are asked to rate whether these statements are applicable to them during the last week, answering 'yes' or 'no'. The range of the cumulative score is 0 to 30; scores labelled: 0-9 as 'not depressed', 10-19 as 'mildly depressed', and 20-30 as 'severely depressed'.

All primary and secondary outcomes will be assessed at 1 pre-randomisation assessment and 4 half-yearly post-randomisation assessments (i.e. 2 years of follow-up).

1. Subjective sleep is measured with the Athens Insomnia Scale, the Dutch Sleep Disorders Questionnaire and the Pittsburg Sleep Quality Index
2. Cognition is measured with a neuropsychological test battery
3. 24-hour recording of skin temperature (9 temperature loggers are placed on thighs, abdomen, soles of the hands and feet), and of heart rate
4. Two weeks monitoring of rest-activity rhythms by actometry
5. Bed times are estimated with a pressure pad connected to a data logger, placed on the patients' bed
6. Saliva samples are collected on one day, from which the diurnal pattern of cortisol levels are determined
7. The primary caregiver fills out the Zarit Burden Interview and the Self-Perceived Pressure from Informal Care questionnaire

All primary and secondary outcomes will be assessed at 1 pre-randomisation assessment and 4 half-yearly post-randomisation assessments (i.e. 2 years of follow-up).