Sleep Evaluation Before and After Metabolic Surgery

The SLEEP-BAM study is a single-center, within-subject longitudinal observational cohort study designed to evaluate sleep quality before and after primary metabolic surgery. The study will be conducted at Catharina Hospital Eindhoven, the Netherlands, a high-volume center for metabolic surgery.

Sleep disturbances are common in patients with obesity and may include poor sleep quality, insomnia symptoms, excessive daytime sleepiness, disrupted sleep timing, and obstructive sleep apnea. In routine metabolic surgery care, sleep evaluation is often focused mainly on obstructive sleep apnea screening, while other aspects of sleep are less frequently assessed. Metabolic surgery may improve sleep quality through weight loss, improvement of obesity-related comorbidities, and changes in metabolic health, but the longitudinal trajectory of sleep quality after surgery remains insufficiently understood.

Participants will be adults scheduled for primary metabolic surgery, including Roux-en-Y gastric bypass, sleeve gastrectomy, and, if performed within standard care, one-anastomosis gastric bypass. Revisional bariatric procedures are excluded. The study does not assign participants to a treatment or intervention. Surgery is performed as part of routine clinical care, independent of study participation.

Each participant will undergo two measurement periods. The first measurement period will take place before surgery, between 3 months and 2 weeks preoperatively. The second measurement period will take place approximately 1 year postoperatively. The 1-year postoperative measurement was chosen to align with the period in which substantial postoperative weight loss has usually occurred and with standard follow-up in the metabolic surgery care pathway.

During each measurement period, participants will wear two devices at home for 5 consecutive nights. The Garmin Index Sleep Monitor will be used to collect consumer-grade sleep outcomes, including the Garmin Sleep Score, total sleep time, sleep efficiency, sleep latency, nocturnal awakenings, sleep stages, and sleep timing parameters. The viQtor research device will be used to collect physiological signals, including photoplethysmography-based parameters such as oxygen saturation and heart rate variability, as well as raw photoplethysmography signals for exploratory analysis.

A valid night is defined as a night with at least 4 hours of usable recording during the participant's sleep period, based on the sleep diary and/or device-detected sleep period. At least 3 valid nights are required per measurement period. Evening wake-time recordings before sleep onset alone are not sufficient to define a valid night.

The primary outcome is the change in Garmin Sleep Score from preoperative baseline to 1 year after metabolic surgery. The Garmin Sleep Score is a device-derived composite score ranging from 0 to 100. It reflects several sleep-related aspects, including sleep duration, sleep stages, restlessness, and related metrics. The score is used as a pragmatic longitudinal measure of sleep quality in the home setting and is not considered equivalent to polysomnography or a diagnostic measure of sleep disorders.

Secondary outcomes include changes in objective sleep parameters, such as total sleep time, sleep efficiency, sleep latency, percentage of rapid eye movement sleep, nocturnal awakenings, peripheral oxygen saturation, heart rate variability, bedtime, wake time, mid-sleep time, sleep timing variability, and sleep regularity. Subjective sleep outcomes include the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Hospital Anxiety and Depression Scale, and sleep diary-derived parameters. Quality of life will be assessed using the OBESI-Q. Clinical outcomes include postoperative weight loss, expressed as percentage total weight loss.

The study will compare subjective sleep reports with objective wearable-derived sleep measures. It will also explore the association between changes in sleep quality and postoperative weight loss, while considering clinical variables such as age, sex, baseline body mass index, type of surgery, comorbidities, medication use, and quality of life. An exploratory analysis of raw photoplethysmography signals from the viQtor device will assess signal quality and examine whether derived research features correlate with Garmin sleep metrics. This exploratory analysis is intended as an early step toward potential development of sleep-related parameters and is not intended for diagnostic validation.

The planned sample size is 50 participants. The sample size was based on a paired within-subject comparison for the primary outcome, with an assumed moderate effect size. The target sample size includes an allowance for incomplete wearable recordings, insufficient valid nights, and loss to follow-up.

The study has received ethical approval from Medical Research Ethics Committees United under registration number R26.043. Participants will provide written informed consent before any study-specific procedures are performed. Participation is voluntary and withdrawal from the study will not affect standard medical care.

Inclusion criteria

• Age 18 years or older.
• Body mass index (BMI) of 40 kg/m² or higher, or BMI of 35 kg/m² or higher with obesity-related comorbidities.
• Scheduled for primary metabolic surgery, including Roux-en-Y gastric bypass, sleeve gastrectomy, or, if performed within standard care, one-anastomosis gastric bypass.
• Willing and able to wear wearable devices for 5 consecutive nights during both study measurement periods.
• Willing and able to complete sleep questionnaires and a daily sleep diary.
• No shift-based or irregular night-shift work schedule that could interfere with sleep measurements.
• Able and willing to provide written informed consent.

Exclusion criteria

• Revisional bariatric procedure.
• Diagnosed obstructive sleep apnea currently treated with continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP).
• High clinical suspicion of obstructive sleep apnea during the standard preoperative work-up requiring further diagnostic evaluation or treatment.
• Chronic preoperative use of medications that may significantly alter sleep quality, including benzodiazepines, zolpidem, or other sedatives or sleep aids.
• Unable to complete the study procedures or comply with wearable device use, questionnaires, or sleep diary completion.