Introduction: Patients with dementia may suffer from poor sleep quality. Disturbance in the metabolism melatonin may have a role in the pathogenesis of sleep-wake cycle alterations in dementia.

Objective: To evaluate the efficacy of low dose exogenous melatonin in improving sleep quality.

Design: A single-center randomized, double-blinded, placebo-controlled study carried out on outpatients with dementia and sleep alterations.

Participants: The investigators calculated a 40 individuals aged 65 years or over with a diagnosis of mild-moderate dementia (Clinical Dementia Rating 1-2).

Intervention: Patients were randomized to receive either 5 mg of melatonin or placebo every night for 8 weeks.

Measurements: The primary outcome was sleep quality according to the Pittsburgh Sleep Quality Index (PSQI).

This is a single-center study. The study protocol, informed consents, and amendments were approved in writing by the appropriate local site Independent Ethics Committee (IEC)/Institutional Review Boards (IRB) (Ethics Committee of the Universidad Autónoma de Nuevo León, School of Medicine).

The patients were recruited as outpatients from the Geriatrics Clinic. A total of 67 patients were screened out of which 40 male and female patients diagnosed with mild to moderate dementia were recruited to the study. Following inclusion, all patients underwent randomization to treatment with melatonin (5 mg orally) or placebo for 8 weeks. To prevent bias, matching placebo tablets, which were identical in appearance, taste, and odor, were used. The treatment was double-blinded, with two parallel treatment groups. Selection for a treatment group was determined by a computer-generated randomization list, in a 1:1 ratio using the randomized permuted blocks method.

Inclusion Criteria:

• Older than 60 years;
• Circadian cycle sleep disorder with insomnia (according to Diagnostic and Statistical Manual of Mental Disorders- V criteria);
• Mild or moderate dementia (clinical dementia rating 1 and 2);
• Medications such as anti-depressants, acetylcholinesterase inhibitors, antipsychotics or memantine were allowed as long as they were initiated for over 8 weeks.

Exclusion Criteria:

• They had other diagnoses of sleep disorders, known hypersensitivity to melatonin, use of stimulants or hypnotics, recent diagnosis (within 8 weeks) of mood disorders or neuropsychiatric symptoms.

Selection for a treatment group was determined by a computer-generated randomization list, in a 1:1 ratio using the randomized permuted blocks method.