Couples Health Aging, Rhythms and Sleep Study

Inclusion Criteria: * Married or partnered in a romantic relationship, cohabiting for at least two years * age \>50 * smartphone user * one partner meets criteria for cognitive impairment without severe impairment in daytime dysfunction according to telephone screening, while other partner must not meet this criteria for impairment. Exclusion Criteria: * Unstable or severe medical or psychiatric conditions that would interfere with study participation (including but not limited to current cancer treatment, psychosis, history of major stroke, head injury with loss of consciousness \>30 min, other neurologic/systemic illness that may affect cognition, alcohol or other substance abuse) * current use of antipsychotic or anticonvulsant medications * inadequate vision, hearing, or dexterity to participate in the assessment * night shift work \>1x per month (defined as beginning work after 9:00 pm or work in the overnight hours \[12:00 am-5:00 am\])