Transition into Daylight Savings Time (DST) affects sleep pattern and functionality

    

    Circadian Rhythms are physical, mental, and behavioral changes that follow a roughly 24-hour cycle that responds primarily to light and darkness in an organism’s environment (National Institute of Health, 2008). One factor that causes disruption to circadian rhythms is daylight savings time switch during the spring season, where there is an hour of time lost. This change causes disruption to sleep patterns; i.e. loss of sleep, as well as disruption in functionality; i.e. inability to perform a task effectively. In the current study, it is hypothesized that the daylight savings time switch affects sleep pattern and functionality. Twenty three subjects; nine males and fourteen females, between the ages of twenty one and thirty seven (mean age = 26.2 years), completed the study. Subjects kept track of their sleep pattern by filling out a five variable; time in bed, time out of bed, sleep latency, amount of sleep, and fatigue rate, sleep log for a total of fifteen days; ten days acquired during the two weekends prior to the DST switch (baseline condition), and five days acquired the weekend during which the DST switch occurred (experimental condition). A paired-samples t test design was employed for analysis that compared subjects sleep pattern and functionality during the daylight savings time switch to prior to the switch occurring. The results show that during the weekend that the daylight savings time switch occurred, participants experienced more fatigue, took less time to fall asleep, and slept less during the night. The findings of this study were supported by previous literature which suggests that delayed sleep pattern affects sleep and morning function (Yang and Spielman, 2001). It also gave way to possibility of conducting future research in the area of daylight savings time such as how daylight savings time switch affects individual’s time of day (morning or evenings) preference for sleep and functioning.

Transition into Daylight Savings Time (DST) affects sleep pattern and functionality 

    Circadian Rhythms are physical, mental, and behavioral changes that follow a roughly 24-hour cycle that responds primarily to light and darkness in an organism’s environment (National Institute of Health, 2008). It is found in most organisms and when disrupted it is capable of changing sleep-wake cycles, the release hormones, body temperature and other important bodily functions (National Institute of Health, 2008). One factor that causes disruption to circadian rhythms is daylight savings time switch during the spring season where there is an hour of time lost. This change in time affects circadian rhythms which in turn causes disruption to sleep patterns; i.e. loss of sleep, as well as disruption in functionality; i.e. inability to perform a task effectively. Kalat (1995) reported on a study conducted by Kleitman (1963), who established that changes in circadian rhythm affects sleep pattern in humans. Using a twenty eight hour a day schedule for two subjects, Kleitman showed that one subject had trouble awakening at scheduled times and the other had trouble sleeping and could not adjust to the twenty eight hour a day schedule.

Valdez, Ramirez, and Garcia (2003) also conducted a study to examine if how small changes in sleep; losing an hour or two, have a large impact on sleep patterns. The researchers found that some individuals did not immediately adapt to DST and took several days in order to do so, and thus altering their sleep pattern.

To better understand the impact of daylight savings time (losing an hour of time) on sleep patterns and functionality, a study was conducted using a paired-samples t test design in which subjects recorded their sleep pattern as well as their fatigue rate, for days that included two weekends prior to the daylight savings time switch and one weekend during which the time switch occurred. We hypothesized that the daylight savings time switch affects sleep pattern and functionality.

Method
Participant

    Initially, twenty four subjects; ten males and fourteen females, were included in this study. However, one participant was terminated due to failing to report their sleep log. Twenty three subjects; nine males and fourteen females, between the ages of twenty one and thirty seven (mean age = 26.2 years), completed the study. Each of the participants that took part in the study met the following requirements: All participants were City College Graduate Students attending experimental psychology class, and were identified using a six code system in the form of a constant-vowel-constant-number-number-number; i.e. DAN012.

Design

    Two conditions were conducted in the study; a control (baseline) condition and an experimental condition, and each subject participated in both conditions. In the baseline condition; sleep pattern prior to Daylight Savings Time (DST) switch, subjects were required to report their average of ten days sleep pattern which occurred during the two weekends prior to the DST switch, and in the experimental condition; sleep pattern during Daylight Savings Time (DST) switch, subjects were required to report their average of five days sleep pattern which occurred the weekend during the DST switch. An analysis of the data was then preformed using a Paired-Samples T Test design.

Measures
    Subjects were required to fill out a sleep log that consisted of five sleep variables; time in bed, time out of bed, sleep latency, amount of sleep, and fatigue level. Each of these variables were divided into the two conditions described above; sleep pattern during the two weekends prior to the DST switch; (baseline) condition, and sleep pattern during the weekend the DST switch occurred; (experimental) condition.

Procedures

    The study consisted of two procedures: The first procedure involved subjects keeping track of their sleeping patterns by filling out a sleep log (attached) for a total of fifteen days. Ten days of the sleep log data was acquired during the two weekends prior to the DST switch, and five days of the sleep logs were acquired the weekend during which the DST switch occurred. Sleep logs were recorded each week beginning on Friday and ending on Tuesday. Data for Friday was recorded on Saturday, Saturday’s data was recorded on a Sunday, Sunday’s data was recorded on a Monday, and so forth, until the appropriate fifteen days worth of data was accounted for.

In addition, the sleep variables (described above) with the exception of fatigue were measured using standard time units (hours: minutes: seconds). The fatigue level was measured on a Likert Scale ranging from one (lowest fatigue) to ten (highest fatigue).

The second procedure of the study required each participant to convert their data in order to find the average of their week’s log: the average of the two weekends (combined) prior to the DST switch, and the average of the weekend during which the DST switch occurred. Investigators then pooled their data and formed one complete data sheet to conduct appropriate analysis.

However, it is important to note that before the analysis was conducted, the sleep variable; “Time in Bed”, was converted from standard time units to minutes before and after 12 o’clock midnight. The time was therefore based on direction. For instance, if a subject reported that they entered into bed at 11:00:00 p.m., using 12:00:00 a.m. as the center point, their time in bed would be recorded as – 60 minutes. Similarly, if their time in bed is 1:00:00 a.m. it would be recorded as 60 minutes. The above process allowed the investigator to clearly identify the time of day (a.m. or p.m.) subjects entered into bed.

Results

    It was hypothesized that Daylight Savings Time (DST) switch will affect sleep pattern and functionality. The data from the study was analyzed using a “Paired-Samples T Test design.” The results were as follows:

The mean time in bed for subjects during the weekends prior to the Daylight Savings Time (DST) switch was; (M = 0:100:09 = 1:40:09 a.m. [S.D. = 0:235:625 = 4:05:25 a.m.]); the mean for subjects during the weekend of DST switch was; (M = 0:75:48 = 1:15:48 a.m. [S.D. = 0:98:300 = 1:43:00 a.m.]) (See table 1). This difference was not statistically significant, (t (22) = 1.57, p > .05). During the DST switch participants entered into bed approximately the same time as prior to the time switch occurring.

Paired Samples Statistics
		Mean	N	Std. Deviation	Std. Error Mean
Pair 1	TIB - Prior to DST switch	100.09	23	235.625	49.131
	TIB - During DST switch	75.48	23	98.300	20.497

Analysis also showed that there was no difference (t (22) = .92, p > .05), in the time out of bed for participants prior to the DST switch; (M = 8:41:45 a.m. [S.D. = 1:22:03 a.m.]), and during the DST switch; (M = 8:26:13 a.m. [S.D. = 2:01:29 a.m.]) (see Table 2). Participants woke up at approximately the same time during both conditions; prior to and during the daylight savings time switch.

Paired Samples Statistics
		Mean	N	Std. Deviation	Std. Error Mean
Pair 1	TOB - Prior to DST switch	8:41:45.652	23	1:22:03.191	0:17:06.556
	TOB - During DST switch	8:26:13.043	23	2:01:29.174	0:25:19.898

    

 There was however a significant difference between the baseline and experimental conditions among three of the sleep variables; sleep latency, amount of sleep, and fatigue rate. The mean sleep latency for subjects during the weekends prior to the DST switch was; (M = 0:17:31 [S.D. = 0:12:08]); the mean for subjects during the weekend of DST switch was; (M = 0:14:28 [S.D. = 0:11:02]) (see Table 3). This difference was statistically significant, (t (22) = 2.07, p = .05). During the weekend that the DST switch occurred, participants took less time to fall asleep than they did the weekends prior to the DST switch.

Paired Samples Statistics
		Mean	N	Std. Deviation	Std. Error Mean
Pair 1	SLAT - Prior to DST switch	0:17:31.261	23	0:12:08.203	0:02:31.841
	SLAT - During DST switch	0:14:28.609	23	0:11:02.859	0:02:18.216

    The mean amount of sleep for subjects during the weekends prior to the DST switch was; (M = 7:45:53 [S.D. = 0:55:35]); the mean for subjects during the weekend of DST switch was; (M = 7:22:20 [S.D. = 0:53:22]) (see Table 4). This difference was statistically significant, (t (22) = 3.20, p < .01). Participants slept more during the weekends prior to the DST switch than they did during the weekend the DST switch occurred.

Paired Samples Statistics
		Mean	N	Std. Deviation	Std. Error Mean
Pair 1	Amt Of Slp - Prior to DST switch	7:45:53.478	23	0:55:35.572	0:11:35.515
	Amt Of Sleep - During DST switch	7:22:20.870	23	0:53:22.644	0:11:07.797

The mean fatigue rate for subjects during the weekends prior to the DST switch was; (M = 3.72 [S.D. = 1.12]); the mean for subjects during the weekend of DST switch was; (M = 4.26 [S.D. = 1.34]) (see Table 5). This difference was statistically significant, (t (22) = 3.00, p < .01). Participants were more fatigued during the weekend the DST switched occurred compared to the weekends prior to the DST switch.

Paired Samples Statistics
		Mean	N	Std. Deviation	Std. Error Mean
Pair 1	FR - Prior to DST	3.7174	23	1.12033	.23360
	FR - During DST Switch	4.2609	23	1.33544	.27846

Discussion

    The current study has shown that daylight savings time switch significantly affects the time it takes to fall asleep, the total amount of sleep, as well as the fatigue rate experienced by subjects. During the weekend that the daylight savings time switch occurred, participants experienced more fatigue, and took less time to fall asleep. However, they slept less during the night. These findings suggest that the circadian rhythm is disrupted by time and that this disruption impacts sleep pattern and functionality.

The findings of this study were particular interesting for two reasons: First it is supported by previous literature and second, it gives way for the development of new theories in future research. Earlier findings in research suggest that changes in time affects sleep pattern and functionality. Yang and Spielman (2001) conducted a study on how delayed sleep pattern affect sleep and morning function. They delayed subjects’ sleep pattern by two hours on Friday and Saturday night and found that subjects had a harder time sleeping Sunday night as well as experienced lower cognitive performances on Monday. In addition, a study done by Barnes and Wagner (2009) showed that changes to daylight savings time not only hindered sleep (losing an hour), but also led to higher injuries in the workplace.

The findings in this study can be use to possibly conduct a more in-depth research in the area of daylight savings time and how it may affect individuals time of day (morning or evenings) preference for sleep and functioning. While there is little research on morning or afternoon preference and daylight savings time, Schneider and Randler (2009) found that daylight savings time transition caused higher day time sleepiness for those adolescents who prefer evenings.

The results of the current study show that there may be other factors that may impact individual’s sleep pattern and functionality. Two of those factors are substance use and behavioral activities. Participants in this study may have attended social events or worked a night shift schedule which will in turn affect their sleeping pattern as well as their functionality. In addition, substance use may have also accounted for the difference in sleep pattern and functionality between the two conditions; weekends prior to DST switch and the weekend during which the DST switch occurred. Participants may have hindered their sleep pattern and functionality by taking substances such as caffeine, sleeping medication and alcohol.

Reference

Barnes, C. M. & Wagner, D. T. (2009). Changing to daylight savings time cuts into sleep and increases workplace injuries. Journal of Applied Psychology, 94(5).

Kalat, J. W. (1995). Biological psychology. Pacific Grove, CA.

Schneider, A. & Randler, C. (2009). Daytime sleepiness during transition into daylight saving time in adolescents: Are owls higher at risk? Sleep Medicine, 10.

The National Institutes of Health. (2008). Circadian rhythms fact sheet. Retrieved from: http://www.nigms.nih.gov/Education/Factsheet_CircadianRhythms.htm

Valdez, P., Ramirez, C., and Garcia, A. (2003). Adjustment of the Sleep-wake cycle to small (1-2hr) changes in schedule. Biological Rhythm Research, 34(2).



Yang, C. & Spielman, A. J. (2001). The effect of a delayed weekend sleep pattern on sleep and morning functioning. Psychology & Health, 16(6).