Sleep Quality and Cognitive Functions in Adults: A Cross-Sectional Study

This study is designed as an observational, cross-sectional investigation conducted in healthy young adults to examine the association between sleep quality and cognitive functions. Participants will be recruited from a non-clinical population and will undergo a single assessment period. Subjective sleep quality will be assessed using the Pittsburgh Sleep Quality Index (PSQI), a self-report questionnaire evaluating sleep quality and sleep-related disturbances over the previous month. In addition to subjective measures, objective sleep parameters will be collected using a wearable device worn continuously for five consecutive days. Wearable-derived sleep metrics will include total sleep time, sleep efficiency, sleep onset latency, and wake after sleep onset, as provided by the device's standard algorithms. Cognitive functions will be evaluated during a single in-person assessment session following completion of the sleep data collection period. Cognitive assessment will include standardized neuropsychological tests measuring attention, executive functions, and verbal memory. Attention and executive functions will be assessed using the Victoria Stroop Test, and verbal memory processes will be evaluated using the Öktem Verbal Memory Processes Test, administered according to standardized procedures. Demographic information and relevant background variables will be collected to characterize the study sample. Statistical analyses will primarily focus on examining associations between subjective and objective sleep parameters and cognitive test outcomes. Correlation analyses and multivariable statistical models may be used to explore relationships between sleep quality and cognitive performance while accounting for potential confounding variables. This study aims to contribute to the understanding of how variations in sleep quality are associated with cognitive functioning in healthy young adults, using both subjective and objective sleep measures.

Inclusion criteria

• Between 18 and 35 years.
• Ability and willingness to provide written informed consent.
• Sufficient ability to read, understand, and communicate in Turkish, the language in which the assessments are administered.
• Self-reported good general health, with no active medical or psychiatric conditions that significantly affect daily functioning.
• Willingness and ability to wear a wearable sleep monitoring device continuously for five consecutive days and to comply with device usage instructions.
• Ability to attend and complete a single-session cognitive assessment

Exclusion criteria

• Regular or frequent use of medications known to affect sleep or cognitive function, including sedative-hypnotics, benzodiazepines, antipsychotics, stimulants, opioids, or similar agents.
• Initiation of, or dose changes in, psychotropic medications within the past four weeks.
• Being under the influence of alcohol or illicit substances on the day of cognitive testing.
• Engagement in night shift work or rotating shift schedules within the past one month.
• Travel across time zones resulting in a time difference of two hours or more within the past two weeks.
• Uncontrolled high daily intake of caffeine (e.g., >400 mg/day) and unwillingness to reduce consumption during the study period.
• Color blindness or other color vision deficiencies, due to their potential impact on Stroop Test performance.
• Dermatological conditions, allergies, or skin lesions at the wrist that prevent wearing the device, or refusal to wear the device as required.
• Acute illness within the past two weeks, including febrile infections, severe pain, or other acute medical conditions that may temporarily affect sleep or cognitive performance.
• Pregnancy or early postpartum period.