The sounds you wake up to could be affecting how groggy and clumsy you are in the morning


Beep beep beep or Beach Boys?

The sounds you wake up to could be affecting how groggy and clumsy you are in the morning, according to new research.

A study by RMIT University suggests melodic alarms could improve alertness levels, with harsh alarm tones linked to increased levels of morning grogginess.

The surprising finding, published in PLoS One, could have important implications for anyone who needs to perform at their peak soon after waking, such as shift workers and emergency first responders.

Lead author, RMIT doctoral researcher Stuart McFarlane, said morning grogginess – or sleep inertia – was a serious problem in our 24-hour world.

“If you don’t wake properly, your work performance can be degraded for periods up to four hours, and that has been linked to major accidents,” McFarlane said.

“You would assume that a startling ‘beep beep beep’ alarm would improve alertness, but our data revealed that melodic alarms may be the key element. This was unexpected.

“Although more research is needed to better understand the precise combination of melody and rhythm that might work best, considering that most people use alarms to wake up, the sound you choose may have important ramifications.

“This is particularly important for people who might work in dangerous situations shortly after waking, like firefighters or pilots, but also for anyone who has to be rapidly alert, such as someone driving to hospital in an emergency.”

The research involved 50 participants, using a specially designed online survey that enable them to remotely contribute to the study from the comfort of their own home.

Each person logged what type of sound they used to wake up, and then rated their grogginess and alertness levels against standardised sleep inertia criteria.

Co-author Associate Professor Adrian Dyer, from RMIT’s School of Media and Communication and Digital Ethnography Research Centre, said the research could help contribute to the design of more efficient interventions for people to use on their own devices to wake up properly.

“This study is important, as even NASA astronauts report that sleep inertia affects their performance on the International Space Station,” Dyer said.

“We think that a harsh ‘beep beep beep’ might work to disrupt or confuse our brain activity when waking, while a more melodic sound like the Beach Boys ‘Good Vibrations’ or The Cure’s ‘Close to Me’ may help us transition to a waking state in a more effective way.

“If we can continue to improve our understanding of the connection between sounds and waking state, there could be potential for applications in many fields, particularly with recent advancements in sleep technology and artificial intelligence.”

The study, ‘Alarm tones, music and their elements: Analysis of reported waking sounds to counteract sleep inertia’, with co-authors Dr Jair Garcia (School of Media and Communication) and Dr Darrin Verhagen (School of Design), is published in PLoS ONE.

Life evolved on our planet under the influence of environmental cycles. Earth rotation produces a daily cycle, in which light and temperature increase during the day and decrease during the night.

Additionally, the Earth revolves around the sun producing another cycle manifested as the seasons of the year. Organisms on Earth adapted to the cycles in the environment through the development of internal oscillations, known as biological rhythms.

The most studied biological rhythm is the circadian rhythm, with a period close to 24 h [1]. When an organism remains in a constant environment (constant darkness, constant temperature) for a prolonged interval, almost all physiological activities oscillate with a period close to, but still different from, 24 h [2].

In mammals, the lesion of the suprachiasmatic nuclei of the hypothalamus eliminates the circadian rhythms, indicating that this cerebral structure operates as a biological clock and as a pacemaker that keeps all physiological functions internally synchronized [3].

Most organisms adjust their circadian rhythm to the natural 24 h environmental cycle through synchronizers, such as the light-dark cycle, the temperature cycle, the feeding cycle, and the social stimulation cycle [4].

The light-dark cycle is the most potent synchronizer of circadian rhythms for the majority of species, including human beings [5].

The endogenous nature of the circadian rhythm is supported by the discovery of clock genes in many species, that are related to different parameters of the circadian rhythm [6].

Circadian rhythms are a biological property of all living organisms, these are oscillations in many physiological variables, such as body temperature, melatonin or cortisol secretion, or even in motor activity, and can be recorded in each member of a given species.

Physiological variables can also show acute variations due to changes in the environment; for example, a mammal may run suddenly to escape from a predator, the intense exercise while running raises body temperature for several minutes, but then the effect dissipates and thus the body temperature resumes its circadian oscillation.

These transitory changes affecting physiology produce a masking effect on circadian rhythms [7]. Many environmental factors may modify physiological variables producing a masking effect, sometimes even interfering with the recording of circadian rhythms.

Therefore, studying circadian rhythms requires the recording of physiological variables and cognitive processes in constant conditions.

Circadian rhythms are also present in most of the physiology of human beings. In humans, there are circadian rhythms in body temperature, cardiac, pulmonary and metabolic activity, nervous system activity of many areas of the brain, the secretion of all hormones, such as melatonin or cortisol, and the sleep-wake cycle [8].

Circadian rhythms can be observed in the performance of most tasks and activities recorded thus far in humans, such as sensory, motor, reaction time, time estimation, memory tasks, verbal tasks, arithmetic calculations, and simulated driving tasks [9].

Performance increases during the day and decreases during the night. Variations in human performance may be the result of circadian rhythms in cognitive processes that are crucial for the execution of all that tasks [10].

One of these basic cognitive processes is attention. Patients with brain injury suffering a reduction of attention show an impairment in the performance of most tasks and neuropsychological tests [11].

This paper reviews the recent results on circadian rhythms in attention, as well as the implications of these rhythms for real-life conditions.

Homeostatic and Circadian Factors

Human physiology and cognitive performance in humans depend on two factors: homeostatic and circadian [12].

The homeostatic mechanisms maintain a set point level for any physiological function, while the circadian clock produces regular oscillations of the same function.

As an example, even though environmental temperature shows variations, core body temperature tends to remain close to 36.5 degrees Celsius.

Concurrently, a circadian rhythm in core body temperature of around one degree occurs, with higher values at daytime and lower values during nighttime. This rhythm appears to be irregular or noisy on a natural setting, this is due to changes in ambient temperature, exercise or food consumption, that affect body temperature moment by moment, thus producing masking effects; but the rhythm becomes very regular when the organism remains in constant environmental conditions. Sleep, sleepiness, and performance also change during the day due to the interaction between these two factors [13].

Homeostatic regulation of sleep and cognitive performance refers to the fact that after sleeping well, people wake up alert and active. However, as the day advances people report feeling less alert, at the end of the day sleepiness increases and they fall asleep.

When people do not sleep well, they feel less alert and suffer an increase in daytime sleepiness. Alertness increases after the person sleeps efficiently again.

The circadian regulation of sleep and cognitive performance refers to the near 24 h period cycle present in alertness and sleepiness.

During daytime hours, alertness is high and sleepiness is low, whereas the opposite occurs during nighttime. Sleepiness is commonly regarded to have detrimental effects on performance at school or work.

But sleepiness is a self-report of the subjective feelings of a person during a specific physiological condition.

In other terms, during nighttime the core body temperature and the brain activity diminish, this induces a reduction in cognitive processing that the person interprets as a sensation of subjective sleepiness.

Kleitman proposed a theory to explain the origin of cognitive performance rhythms. His theory asserts that the circadian rhythm in metabolic activity modulates brain activity, producing oscillations in cognitive performance [14].

Some cognitive processes show oscillations with a phase similar to the body temperature rhythm [15], but other cognitive processes show a 1 to 4 h phase delay with respect to the body temperature rhythm [16].

It is possible that several oscillators in the brain [17] drive the cycles of different cognitive processes, although all cycles remain coupled to the suprachiasmatic nuclei, which operates as the pacemaker of a multi-oscillatory circadian system.

Alertness (Tonic and Phasic)

Many papers have documented homeostatic and circadian variations in alertness, using undemanding tasks such as a simple reaction task or vigilance tasks [27].

An example of a simple reaction task is the Psychomotor Vigilance Test, which is used in many studies on circadian rhythms to document changes in cognitive performance. Homeostatic and circadian changes have been demonstrated with this task using time of day, constant routine, and forced desynchronization protocols.

Main changes observed are an increase in reaction time throughout the day and circadian variations in reaction time, with lower response latency during the day and higher response latency during the night.

The number of lapses (omissions or responses with longer reaction times) also increases with time awake and show circadian variations, with fewer lapses during daytime and a higher frequency of lapses during nighttime [15,28,29].

Homeostatic and circadian variations in tonic and phasic alertness have been observed using a continuous performance task, on a constant routine protocol [22].

Attention requires processing of a single stimulus or several stimuli occurring successively. Processing new incoming information implies that attention should be shifted from one stimulus to another [30].

This process takes time and reduces the efficiency to process the new event [31]. When two stimuli occur with an interval of one second or longer between them, people have no problem to efficiently process both stimuli.

But when they occur with a short interval between them (less than 500 ms), people respond accurately and rapidly to the first stimulus, but require more time or fail to process the second stimulus. So, a longer reaction time and less correct responses occur to the second stimulus occurring at an interval shorter than 500 ms, indicating a reduction in the capacity to process the new stimulus.

These changes in the processing of a new stimulus have been measured through the Psychological Refractory Period (PRP) [32] and the Attentional Blink (AB) [33]. The PRP is an increase in the reaction time required to process a second stimulus occurring within a 500 ms interval after the first stimulus.

Circadian variations have been observed in the PRP [34], this study recorded the PRP every 2 h, during 28 h, on a constant routine protocol. Two stimuli were used: Stimulus 1 (S1) was a 300 or 900 Hz tone, and stimulus 2 (S2) was an X or O letter.

Three intervals were used between S1 and S2: 50, 200, or 1000 ms. Participants had to make a specific response to each stimulus. Results showed that accuracy was constant throughout sessions, whereas reaction times to both stimuli showed an increase during the night.

Changes in time of day were observed in the PRP gradient, obtained by subtracting the reaction time to S2 at the 1000 ms interval from the reaction time to T2 at the 50 ms interval. This finding suggests that there are circadian oscillations in central processing time, which may explain the circadian variations in reaction time observed in many other studies.

The changes in central processing time and reaction time are compatible with circadian variations in tonic alertness. The AB refers to a decrease in the accuracy to detect or identify a second stimulus (target 2, T2) occurring 200 to 500 ms after the first stimulus (target 1, T1). The AB is measured through a Rapid Serial Visual Presentation task, in which an array of stimuli is presented, including two targets (T1, T2) and a group of distractors.

The first (T1) and second targets (T2) are presented within different intervals to measure the accuracy to T2 at each interval, between 100 and 800 ms. Typically, there is a decrease in the accuracy at 200 to 500 ms intervals, while longer intervals (600 to 800 ms) show a high level of accuracy, similar to the accuracy to T1.

Task performance was recorded each hour, during 28 h, in a constant routine protocol. Homeostatic and circadian variations have been found in the accuracy of all the parameters of the RSVP task, used to assess the AB (T1 accuracy and T2 accuracy at all lags) [35].

T1 accuracy is related to the capacity to respond to independent stimuli, at separate times. A reduction in T1 accuracy was observed throughout the recording session, showing time awake (homeostatic) and time of day (circadian) effects.

Circadian variations in T1 showed a phase delay of around 2 h with respect to the circadian rhythm in rectal temperature. Changes in T1 may be related to tonic alertness, which is the general capacity to respond to any stimulus.

Selective Attention

Homeostatic and circadian variations have been observed in selective attention associated with the melatonin circadian rhythm, on a constant routine protocol [36]. Homeostatic (time awake) and circadian (time of day) variations were also observed in selective attention using a continuous performance task, on a constant routine protocol [22].

Homeostatic and circadian variations were also observed in the processing of a second stimulus occurring at a short interval after the first stimulus (T2 accuracy at lag 2, 200 ms) and to successive independent stimuli (T2 accuracy at lag 8, 800 ms) [35].

The changes in information processing observed in this study, may be due to a reduction in the activation to process any stimulus or a reduction in the capacity to suppress the processing of distractors.

Circadian variations in T2 showed a phase delay of around 2 h with respect to the circadian rhythm in rectal temperature. The reduction in the efficacy to process a second stimulus (T2) is compatible with changes in selective attention.

Dual-task and task-switching performance (examples of multitasking) are affected by sleep deprivation [3739] and time of day variations in these types of tasks have been observed [4042].

Sustained Attention

To analyze sustained attention, it is necessary to measure three indices of this cognitive process: general stability of performance efficiency, time on task performance, and short-term stability [43]. General stability of performance efficiency can be measured as the variability (standard deviation) of correct responses throughout a task.

Low variability means a high level of stability of efficiency and an increase in sustained attention. Circadian variations in the stability of performance efficiency have been observed, with high stability during daytime and low stability during nighttime and early in the morning [44]. Time on task performance can be measured by a linear regression coefficient of correct responses throughout the task.

A zero linear coefficient value indicates maintenance of the same level of performance from start to end, meaning an increase in attention. This index of sustained attention decreases with time awake and sleep deprivation [45].

Short-term stability of efficiency can be measured by hit runs (sequences of correct responses) and error runs (sequences of errors). Longer and more frequent hit runs, or less frequent error runs indicate an increase in sustained attention.

A progressive homeostatic decrease during the day has been observed in general stability and short-term stability (hit runs and error runs), using a continuous performance task, on a constant routine protocol, with a decrease between 04:00 to 07:00 h [46].

More information: Stuart J. McFarlane et al, Alarm tones, music and their elements: Analysis of reported waking sounds to counteract sleep inertia, PLOS ONE (2020). DOI: 10.1371/journal.pone.0215788


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