Circadian rhythms are biological processes that display an endogenous cycle of approximately 24 hours. They are influenced by external cues like light and regulated by the brain's circadian pacemaker. Common circadian rhythms include the sleep-wake cycle and fluctuations in body temperature and hormone levels. Disruptions to circadian rhythms can result in circadian rhythm disorders like delayed sleep phase syndrome or jet lag. Nurses play a role in assessing patients' circadian rhythms, providing sleep hygiene advice, and referring patients to specialists when needed.

2. BEDSIDE CLINIC ON
CIRCADIAN RHYTHM
PRESENTED BY
PREMNATH R
IST YEAR MSc NURSING
CNK

3. The term "circadian", was coined by Franz Halberg

4.  The term circadian comes from two Latin
words namely
“circa” means around
“diem/dies” means day
Circadian means “approximately one day’’

5.  4th century BC - Androsthenes
 13th century - The observation of a
circadian or diurnal process in humans is
mentioned in Chinese medical texts .
 1729 - The first recorded observation of
an endogenous circadian oscillation by the
French scientist Jean-Jacques d'Ortous de
Mairan

6.  1896 - Patrick and Gilbert observed that
during a prolonged period of sleep
deprivation, sleepiness increases and
decreases with a period of approximately 24
hours.
 1918 - J.S. Szymanski showed that animals
are capable of maintaining 24-hour activity
patterns in the absence of external cues.
 1994 - Joseph Takahashi discovered the
first mammalian 'clock gene' (clock) using

7. CIRCADIAN RHYTHM
A 24-hour biological rhythm
controlled by a “pacemaker” in the brain
that sends messages to other systems
in the body. Circadian rhythm
influences various regulatory
functions, including the sleep–wake
cycle, body temperature
regulation, patterns of activity such as
eating and drinking, and hormonal and
neurotransmitter secretion.

8. CIRCADIAN RHYTHM
A circadian rhythm is any biological process
that displays an endogenous, entrainable oscillation
of about 24 hours. Although circadian rhythms are
endogenous ("built-in", self-sustained), they are
adjusted (entrained) to the local environment by
external cues called zeitgebers, commonly the most
important of which is daylight.
(wikipedia)

9.  A zeitgeber is any external or environmental
cue that entrains, or synchronizes, an
organism's biological rhythms to the earth's
24-hour light/dark cycle and 12 month cycle
Eg:
◦ Light
◦ Temperature
◦ Social interactions
◦ Pharmacological manipulation
◦ Exercise
◦ Eating/drinking patterns

10.  Zeitgebers induce changes in the
concentrations of the molecular
components of the clock to levels
consistent with the appropriate stage
in the 24-hour cycle, a process
termed entrainment.

12. Biological markers
The classic phase markers for
measuring the timing of a
mammal's circadian rhythm are:
 melatonin secretion by the pineal
gland
 core body temperature

13. Effects of age on Circadian rhythm
 Newborn baby -16 to 20 h
 Child - 10 to 12 h
 Age 10 - 9 to 10 h
 Adolescence - 7 to 7.5 h
 A gradual decline to about 6.5 h develops
in late adult life.
 35 years of age onward, women tend to
sleep slightly more than men

14. CRITERIAS OF A CIRCADIAN RHYTHM
To be called circadian, a biological rhythm
must meet these four general criteria:
 The rhythms repeat once a day (they have a 24-
hour period).
 The rhythms persist in the absence of external
cues (endogenous).
 The rhythms can be adjusted to match the local
time (entrainable).
 The rhythms maintain circadian periodicity
over a range of physiological temperatures; they
exhibit temperature compensation.

15. CIRCADIAN RHYTHM DISORDERS
Circadian rhythm disorders occur
when individuals attempt to sleep at
times that are inconsistent with their
underlying biological clocks.

16. CIRCADIAN RHYTHM DISORDERS
 Intrinsic Circadian Rhythm Disorders.
Delayed Sleep Phase Syndrome (DSPS)
Advanced Sleep Phase Syndrome (ASPS)
Irregular Sleep-Wake Pattern
Non-24-Hour Sleep-Wake Syndrome
 Extrinsic Circadian Rhythm Disorders
Shift Work
Time-Zone Change Disorders

17. Intrinsic Circadian Rhythm
Disorders.
Intrinsic circadian rhythm disorders
refer to desynchronizes between attempts
to sleep and the sleep-wake circadian
rhythm that are due presumably to internal
rather than external causes. These
disorders might result from a weak
circadian rhythm or from an inability to
entrain the rhythm to the environment.

18. Delayed sleep phase
syndrome
 First identified by Weitzman et al. (1981) as
a ‘‘chrono biological disorder with
sleep-onset insomnia.’’
 Sleep-wake circadian rhythm is delayed
compared to the time the individual
attempts to sleep
 Individuals report difficulty falling asleep at
a desired bedtime but have normal sleep if
they attempt to sleep a few hours later.

19. Delayed sleep phase
syndrome
 Individuals with DSPS show late sleep
onset, few awakenings, early wake-up
times when work or social demands are
present, and late (mid afternoon) wake-up
times when there are no such demands
on their time.
 Delayed sleep phase individuals
commonly identify themselves as „„night
people‟‟ and report being most alert
during the late evening and night hours.

20. Advanced sleep phase
syndrome
 Inability to stay awake until the desired
bedtime and inability to remain asleep until
the desired wake-up time.
 Typical sleep onset times are between 6
P.M. and 8 P.M., and no later than 9
P.M., and wake times are between 1 A.M.
and 3 A.M., and no later than 5 A.M.

21. Advanced sleep phase
syndrome
 ASPS is much more common in older
individuals than in the young, and the
complaint of waking up too early in the
morning may be confused with
depression.

22. Advanced sleep phase
syndrome
 The current approach to treating ASPS is
bright light exposure in the evening and
avoidance of light exposure (e.g. wearing
dark, wrap around sunglasses) in the
morning. Bright light exposure in the evening
and the avoidance of bright light in the
morning, it is thought, help to re entrain the
sleep-wake cycle into the circadian rhythm.

23. Irregular Sleep-Wake Pattern
 This rare disorder is characterized by a
variable and disorganized sleep-wake pattern
that suggests the absence of circadian
rhythmicity.
 Sleep is broken into several short sleep
episodes, but the cumulative sleep for a 24-
hour period is at normal levels.

24. Irregular Sleep-Wake Pattern
 Polysomnographic studies show no abnormalities
in sleep parameters except for the short duration
of each episode.
 Common in elderly people with dementia.
 Treatment consists of a gradual decrease in the
number and duration of daily naps. Increase in
activity levels and social interaction is
recommended to facilitate the process.

25. Non-24-Hour Sleep-Wake Syndrome
 This is a disorder in which individuals
are unable to entrain to a 24-hour day
and instead maintain 25- to 27- hour
sleep-wake cycles. Some individuals
with this syndrome tend to
progressively phase delay. The
disorder is rare in the general
population and is assumed to have
higher prevalence among blind
people.

26. Non-24 Hour Sleep-Wake Syndrome
Other names
 Non-24
 Free running disorder (FRD)
 Hypernychthemeral disorder
 Circadian rhythm sleep disorder – free running type
 Circadian rhythm sleep disorder – nonentrained type
 Non-24-hour circadian rhythm disorder
 Non-24-hour sleep-wake disorder

27. Non-24-Hour Sleep-Wake Syndrome
 It is a chronic circadian rhythm sleep
disorder, classified within Chapter VI, Diseases of
the Nervous System, in the ICD 10.
 It can be defined as "a chronic steady pattern
comprising one- to two-hour daily delays in sleep
onset and wake times in an individual living in
society".
 The pattern of delay persists literally "around the
clock", typically taking a few weeks to complete
one cycle.
 This disruption of the body clock causes cyclical
bouts of nighttime sleeplessness and excessive
daytime fatigue and napping.

28. Non-24-Hour Sleep-Wake Syndrome
 Treatment focuses on entraining the
circadian rhythm to a 24-hour day
through social interaction, exposure to
light, and melatonin.
 Melatonin has been successful in
treating this disorder in blind
individuals.

29. Extrinsic Circadian Rhythm Disorders
 Shift Work
 Time-Zone Change Disorders

30. Shift Work Disorder
A disrupted sleep-wake schedule often
results in
disturbed and shortened sleep
sleepiness on the job
reduced performance levels
psychological distress due to disruptions
in family and social life.

31. Time-Zone Change Disorders

32. Time-Zone Change Disorders
 Dyssomnia associated with rapid time-zone
change (‘‘jet lag’’) is due to desynchrony between
the endogenous sleep-wake rhythm and the
light/dark cycle.
 Symptoms include an inability to sustain sleep
and excessive sleepiness.
 For most people, these symptoms subside after a
few days, depending on the number of time
zones crossed.

33. Time-Zone Change Disorders
 Frequent travelers, such as transatlantic airline
crews, may experience more persistent difficulties.
 Westward travel is associated with disturbed sleep
at the end of the sleep period, which coincides
with habitual wakeup time, and eastward travel is
associated with sleep onset insomnia.

34. Time-Zone Change Disorders
 Bright light treatment
 Melatonin administration about an
hour before bedtime in the new time
zone

35. Risk Groups
 DSP is more common in teens and young
adults, occurring at a rate of 16 percent
 ASP is more common as people
age, occurring in about one percent of
middle aged and older adults.
 Irregular sleep-wake rhythm may occur in
nursing home residents and other people
who have little exposure to time cues such
as light, activity and social schedules.

36. Risk Groups
 Free-running (nonentrained) type occurs
in more than half of all people who are
totally blind.
 Jet lag can affect anyone who travels by
air, but symptoms may be more severe
and may last longer in older people and
when anyone travels in an eastward
direction.
 Shift work disorder is most common in
people who work night shifts and early
morning shifts

37. Effects
 Sleep loss
 Excessive sleepiness
 Insomnia
 Depression
 Impaired work performance
 Disrupted social schedules
 Stressed relationships

38. TREATMENT OF CIRCADIAN
RHYTHM DISORDERS
 Behavior therapy or advice about sleep
hygiene.
 Avoid naps, caffeine, and other stimulants.
 Bright light therapy
 Blue blocking glasses therapy
 Medications such
as melatonin and modafinil (Provigil)
 Tasimelteon has been proven effective in
Phase III trials.
 Sleep phase chronotherapy

39. TREATMENT OF CIRCADIAN
RHYTHM DISORDERS
 People who suffer from delayed sleep
phase syndrome are generally unable to
reset their circadian rhythm by moving
their bedtime and rising time earlier.
 In sleep phase chronotherapy, an
attempt is made to move bedtime and
rising time later and later each
day, around the clock, until the person is
sleeping on a normal schedule.

40.  Here's an example of how chronotherapy could
work over a week's course of treatment, with the
patient going to sleep 3 hours later every day until
the desired sleep and waketime is reached.
(Shifting the sleep phase by 3 hours per day may
not always be possible; shorter increments of 1–2
hours are needed in such cases.)
 Day 1: sleep 04:00 to 12:00
 Day 2: sleep 07:00 to 15:00
 Day 3: sleep 10:00 to 18:00
 Day 4: sleep 13:00 to 21:00
 Day 5: sleep 16:00 to 00:00
 Day 6: sleep 19:00 to 03:00
 Day 7 to 13: sleep 22:00 to 06:00
 Day 14 and thereafter: sleep 23:00 to 07:00

41. NURSES RESPONSIBILITY
 Obtain a thorough and careful sleep
history both from patient and partner.
Episodes of parasomnias and other sleep
disorders are unrealized by the patient, but
can be described in detail by the partner
 Ask patient to maintain a sleep diary which
include all sleep histories.
 Maintain a regular and consistent bed time
and wake time that is similar to both
workdays and non-work days

42. NURSES RESPONSIBILITY
 Develop a regular relaxing bed time
routine about 1 to 2 hour before sleep
onset.
 Establish comfortable sleeping conditions
most conducive to good sleep.(cooler
room temperature, darkness, and low
noise levels)

43. NURSES RESPONSIBILITY
 Exercise regularly, but avoid vigorous
exercise within 2 to 3 hours of sleep
onset.
 Spend some time outside each day.
 Avoid exposure to bright light in the
evening before bed and encourage
exposure to bright light in the morning on

44. NURSES RESPONSIBILITY
 Avoid stimulants such as stimulants in
the evening.
 Do not use alcohol to facilitate sleep
initiation; this is likely to result in sleep
fragmentation later in the night as blood
alcohol levels fall.
 Refer patient to a sleep specialists for
diagnostic procedures like
polysomnography actigraphy etc.