Late daytime naps may cause drowsiness after coronary bypass graft operation in the first postoperative week.


S disturbances after coronary artery bypass operations are being widely investigated, but any relationship between the operations and daytime naps has not been thoroughly studied. Daytime napping (in particular afternoon and evening naps) affects total night sleep duration. Thus, increased daytime naps causes a decrease in night sleep time.1 Environmental factors, individual sleep conditions, and postoperative complications have been suggested as the cause of sleep disturbances in coronary artery bypass graft (CABG) surgery patients,2 but none of these studies have investigated the effect of daytime napping on night sleep time. This prospective study is planned in order to investigate whether daytime naps cause a decrease in night sleep and disturb sleep efficiency (SE) after CBAG surgery. In this study, we used the actigraphic nap analysis method to compare coronary bypass operated patients and a healthy control group. Eight-five cases consisting of 45 (23 male and 22 female) patients that underwent CABG operation with cardiopulmonary bypass, and 40 healthy (20 male and 20 female) subjects as controls were evaluated. The study was approved by the institutional ethics committee, and all participants gave their written informed consent. All patients did not have any sleep disturbance and neurologic disorders such as stroke or tremor affecting the non-dominant arm movement (because of the need to wear a wrist Actigraph) or anxiety, and peptic ulcus. None of the patients were taking any drugs related to sleep disorders or central nervous system depressants. A brief psychiatric screening (Hamilton Depression Rating Scale) was completed on each subject. A score of less than 7 was required for participation. Sleep assessment questionnaires were completed by the patients and control subjects in the morning hours. Patients were included in the study for nearly 10 days, including preoperative measurement of the primary study at least 3 days before surgery and a 58 consecutive-day period during the first postoperative week for the study group. Wrist Actigraphs were not used on the operative day and the first postoperative day. The control group subjects wore the wrist Actigraphs for a 7-day period continuously. The sleep instruments used in this study included subjective findings such as a standard sleep diary, Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and objective parameters such as Maintenance of Wakefulness Test (MWT), EEG, and actigraphy. A PSQI score of greater than 5 excluded subjects from the study. An ESS score of equal or greater than 10 was assessed as sleepiness. We applied MWT test for all subjects from 13:00 hours to 21:00 hours in a silent and dim room, to evaluate drowsiness of the subjects. The control and study groups (during pre-and-post-operation periods) were evaluated by EEG with at least 30 minutes periods from 13:00-21:00 hours in a silent and dim room. Subjects in whom sleep parameters were observed on their EEGs were accepted as “light sleep positive”. Actimetric procedures. The actimeter is designed for long-term monitoring of gross motor activity in humans and has an accelerometer capable of sensing motion with a minimal resultant force of 0.01 g.3 Participants wore a wrist actimeter (Actiwatch, AW64®, Mini-Mitter Co. Inc., Bend, OR, USA) on their nondominant wrist in order to examine their motor activity, nap, and sleep analysis. They completed one sleep diary each morning during the period of using actigraphs. These diaries were used to record daily bed times, time of sleep onset, frequency, and duration of awakenings during the sleep period, final awakening time, and napping (sleep outside of the major sleep period) times during the day in order to provide some information about sleep latency (SL), frequency of prolonged awakenings, and total sleep time (TST). The actigraphs were applied to participants’ nondominant wrists on the first postoperative morning and worn continuously throughout the 5-day period in order to evaluate sleep duration and continuity as well as to obtain some information about daytime naps. All watches were calibrated prior to use and set to collect data at 30-seconds epochs, and maximum frequency of 32 Hz according to the criteria used by Sadeh.3 Device sensitivities were determined to indicate that motor activities, ≥ 20 indicates the subject being awake. A minimum of 10 minutes without motor activity after pressing the marker is determined as sleep onset. Counts of motor activities less than 5 are assessed as a sleep period in the analysis of napping. Nap times are determined as a minimum of 15 minutes, similar to the study of Brooks.4 The primary sleep period was recognized based on the times that participants pressed the button on the actimeter, in the evening at lights out and in the morning after waking up, made it possible to log these events. In evaluating nocturnal sleep, the following sleep parameters were estimated: bedtime, wake-up time, sleep-onset time, sleep-offset time, SL, TST, wake time after sleep onset (WASO), and SE. Bedtime and wake-up time were determined from activity scores and sleep logs. Nocturnal sleep interval for scoring was set from bedtime to wake-up time. The SE (nocturnal sleep

1 Figure or Table

Cite this paper

@article{Yilmaz2007LateDN, title={Late daytime naps may cause drowsiness after coronary bypass graft operation in the first postoperative week.}, author={Hikmet Yilmaz and Ihsan Işkesen}, journal={Neurosciences}, year={2007}, volume={12 4}, pages={348-50} }