Circadian Rhythm Sleep Disorder

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Shift work may be termed as different groups or team of workers working on different time of the day, and they usually perform the same type of work so as to ensure continuity in the process or operation. Shift work would normally require workers to work at time that are outside the normal hours of work thought to be between 7am to 7pm. However, shift work system follows a definite and regular pattern and should not be confused with irregular working hours, which include work times in irregular and unpredictable way (Thierry and Meijman, 1994).While there are no sets, agreed upon terms used to definite shift work, yet there are some basic definitions that can be used for the purpose of this study.Day Shift - most common shift for workers, with the hours being between 6 am to 6 pm.Night Shift - the hours being form 11 pm to 6 amFixed Rotating Shift - a work schedule where the shift time changes, usually on a weekly basis or fortnight and the work days worked also change.

This is used in continuous operations.Compressed Work Week - a compressed workweek is when workers work 40 hours per week but in less than 5 days, usually for 10 to 12 hours per day."Shift worker include all people working evening, night rotating, splitting, irregular or on-call schedules especially during the week and weekends "( Institute for Work and Health). Shift work schedules may differ from one place to another and worker may rotate through shifts or remain on a single shift (permanent shift) .

2.1 Circadian Rhythm

While there are many different biological rhythms of different lengths, the most recognized is the 24-hour cycle. These 24 hour cycles are called Circadian Rhythms from the latin circa, for around and dies, for a day. While humans operate on a basically 24-hour clock, these rhythms are not solely determined by light and dark, although lightness and darkness are key elements that regulate our bodies. Human have an internal clock that drives these rhythms. Scientists have now identified several of biological variables in human race that are circadian in nature.

This include body temperature, hormone production, sleep wake circles, and psychological aspect like memory and ability to perform mental tasks."The word circadian comes from the Latin" circa dies" which means "about a day". Circadian rhythms are partly driven by the internal body clocks and partly synchronized to external world by cues known as zeitgebers (German: ziet, time; geber, giver). These rhythms are coordinated to allow for high activity during the day and low activity at night". (Pheasant, 1999)"The circadian rhythm is determined by nucleus suprachiasmaticus in the hypothalamus. This structure regulates the physiology and psychology functions of the body such as temperature. Reaching its maximum at five pm and its minimum at five am.

This basic principle underlying the rhythm variation is catabolism and readiness for action during the day, and anabolism and rest during the night" (Akerstedt, 1996).

2.3 Circadian Rhythm Sleep Disorder

Circadian Rhythm is a problem of timing of a person's and wake when the master clock in the centre of the brain known as the Suprachiasmatic Nucleus(SCN) is disturbed. This internal clock is also responsible for the regulation of temperature and secretion of hormone levels. The main control of the CR is the sleep/wake cycle which lasts a little longer than 24 hours. It is set by visuals cues of light and darkness which transcended along a pathway from eyes to the SCN where it keeps the clock synchronized to the24-hour.

Zietgebers is another time cues which influence the clock's timing include meal and exercise schedules.

2.31 CRSD involves one of these problems:

Hard time to initiate sleepWaking up frequently during night and difficulty to maintain sleepTend to wake up too early and are unable to get back to sleepSleep quality very poor

2.32 Types of CRSD

Delayed Sleep Phase Disorder (DPSD)Advanced Sleep Phase Disorder (ASPD)Shift Work Disorder (SWD)Irregular Sleep-wake Disorder (ISWD)

2.4 Shift Work in the Health Service

Nursing staff are subjected to psychological stress as a result of shift rotation, prolonged work schedules and extensive contact with irritable and depressed patients (Lewy, 1981). In addition, the nature of hospital work forces nurses to undertake important decisions pertaining to patients under conditions where there is no certainty over the events and outcome of the decisions. Nurses may suffer from psychological stress or depression. Therefore the nurse manager should watch the nurses working under his supervision for these behaviours.

Studies have shown that nurses in departments such as intensive care units are more at risk of psychological stress and they are characterised by machinery, high noise level and physical contact with body secretions, infection hazards and unpredictable emergencies (Hay and Oken 1972).An assessment was done to investigate whether nurses are able to manage a 12 hour shift to see if it cause work stress and physical workload for nurses (Makowiec-Dabrowska, et al. 2000). The study was conducted on 536 nurses working a 12-hour shift and 169 working in an 8-hour day shift. Their results showed that the 12-hour system was, characterised by less significant physical workload but increased mental load. The nurses working in a 2-shift system were more tired after work, but they could spend more time on leisure activities and family.

Their data suggested that there are no significant contradictions for nurses to work in a 2-shift system.

2.5 Shift work as a Health and Safety Issue

Interest in the effects of shift-work on people; have developed because many experts have blamed rotating shifts for human error connected to a number of accidents and catastrophes'. Lushington and Dawson, (1997), conducted a study on the perceived social and domestic consequences of shift-work for female shift-workers (nurses). A number of women working non- standard hours have increased over the past few decades. The impact of shift-work on the lives of female workers and their partners; this has less documentation. A standard shift-work questionnaire was administered to a group of female shift-workers (nurses working a variable shift-work roster with night work component), to address this shortcoming.

The female shift-workers and their partners were asked to judge the impact of shift-work on social and domestic life and the perceived impact of shift-work on psychology, social and physiological well- being of the female shift-worker. Overall, a high level of concordance was, observed between the responses of nurses and their partners. Both groups of subjects reported that shift-work had significant negative effect on social and domestic life. Specifically, shift-work was perceived to disrupt the maintenance of joint social activity, increase interpersonal conflict, reduce the quality of interpersonal relationship, and reduce child contact- time for female shift-workers with children.

As well, both groups of subjects indicated that shift-work had significant negative impact on the psychological and social well - being of the female shift-worker. Their results suggested that the impact of shift-work on both social and domestic life and the well- being of the female shift-workers is an important occupational health and safety issue.Any occupational activity or work causes a certain amount of stress. The effects realized between this interconnection, independent of their nature, do cause changes to the environment as well as in the human organism.Changes occurring in the human organism may be significant from a biological point of view. The reduction of such changes to a minimum requires a continuous activity of adaptive mechanisms.

It should be emphasized however, that whether it is the individual who influences the environment or the environment, which produces effects on the organism, in each case it is the human organism that suffers because of stress (Haslegrave et. al, 1990).The causes of stress produced by working conditions may emanate from the environment, often qualified by standards. These effects caused by unfavourable social conditions that may prevail in the workplace are mostly within the control of management. Examples of these are work disorganization, unequal workloads, inadequate professional skills, low wages or salaries compared to workload and job demands. The stress factors associated with tasks are, to a certain extent, limited by labour safety regulations, the contract of labour and the prescriptions of work norms.

These can be regular overtime, increased pace of work, heavy physical work, monotony, responsibility of own physical responsibility of others' physical health, frequent adaptation to others, frequent dangerous situations (Haslegraves et. al, 1990).

2.6 Accidents and Risk of Injury

Shift work systems are known to have an impact on workers' performance. A combination of risk factors led to demonstrate that night shift is associated with increased sleepiness and decreased performance there must logically be an increased risk of accident more particularly at night.Pheasant, (1991) states that the likelihood of error increases when the operator is under abnormal pressure of work, or when the working capacity is reduced because of fatigue. Further explanation is that time of the day may be regarded as a contributory factor which reduces the individual's ability to cope with abnormal circumstances as they arise. People working on night schedule do not sleep well and as a result of sleep loss this can lead to excessive fatigue and sleepiness.

This makes more difficult to perform well, which increases the risk of accidents (Rosa & Colligan, 1998). Shift-workers often develop problems, which do not affect permanent day workers but can develop in the long run because the body has an internal clock (the circadian rhythms) that determine the core body temperature, alertness, cardiovascular system digestion and other systems in the body.

2.7 Sleep

Tepas and Carvalhais (1990) divided working days into three categories: the time worker should be at work, the time to sleep and time-off. Day shift workers use a sequence of sleep, then work and then time off. Afternoon/evening shift workers use the sequence of sleep, followed by time off, and then work. Night shift have the same pattern as evening workers, however it is different in that they have shorter sleep periods which are during the day.

It is common for rotating shift workers to modify their sleep pattern between workdays, non-workdays and days off. So trying to sleep during the day and alternating their sleep between night and day, can lead to problems for the sleep of shift workers.Lack of sleep is one of the main reasons causes reduced functional capacity. After the first 24 hours without sleep the functional capacity may be halved and after two sleepless days, the functional capacity is at its lowest and risk of falling asleep is ever present.

With prolonged exposure, the individual cannot manage to keep awake, and can't make complex decisions which require thinking (Akerstedt, 1996). Nonetheless non experimental research design conducted to examine the effect of sleep on short term memory recall in day shift versus night shift nurses revealed that there is no effect of lack of sleep on cognitive process of short-term memory recall (Allen, 1999).

2.7.1 Sleep of Shift Workers

The most usual complaint among shift workers is "difficulties with sleep". This is due to the sleep disturbances they are subject to (Rutenfranz, Knauth, and Angersbach, 1981). 90% of shift workers investigated talked about sleep disturbances on night shift. When transferred to day work, less than 20% had the same complaint.

The significant reduction in sleep disturbances with the transfer to day work can be accounted to shift work rather than the characteristics of the workers themselves. But yet even after being transferred to day work, workers previously on shift work still complained of sleep related problems (Dumont, Montplaisir, and Infant-Rivard, 1997).Most of sleep difficulties are the result of modified work/rest schedules. Due to reversed sleep/wake cycle, shift workers often sleep during the day. And circadian, environmental and social factors as a combination reduce both the quantity and quality of this day sleep leading to sleep restriction (Scott, 1994). Shift workers' day sleep is shorter than night sleep - less than 6 hours as compared to 7-8 hours at night) thus reducing their total sleeping time (Tepas and Carvalhais, 1990).

Day sleep has decreased objective quality and more frequent arousals, leading to disturbed sleep periods (Scott, 1994). These changes in sleep length during daytime can be imparted to the circadian rhythm at that particular time and which is normally programmed to favour sleep at night as opposed during the day (Âkerstedt and Gillberg, 1981). But the circadian rhythm is not the only responsible to interfere with the workers' day time sleep. Scott, 1994 says that shift workers reduce their sleep time to participate in family or social activities which are in day time. The early start of some morning shifts imply cutting short night sleep to be on time at work, while most shift workers find it difficult to sleep earlier in the evening (Âkerstedt, 1990).

Shift workers have to make with other external factors that are disruptive to their sleep such as traffic and street sounds, phone calls.Being sleepy tends the individual to fall asleep more easily more so on night shift. And this can have catastrophic consequences as the individual is no longer in touch with his surroundings and they can no longer react in case of any potential danger looming (Scott 1994).

2.7.2 Complaints with Sleeping and Sleeping in Shift Work

Harma, Tenkanen, Sjoblom, Alikoski, and Heinsalmi (1998) studied the effect of shift work along with the life style factors (age; smoking; alcohol consumption; and exercise) of shift workers. The data range was 3020 males subject and age range 45 to 60. And the sleep complaints were categorized in 4 groups:InsomniaSleep deprivationDay time sleepinessSnoringThe study showed that complaints were axed towards 39-53% insomnia, 30-45% sleep deprivation, 20-37% day time sleepiness and 38-50% snoring. These complaints were mostly done by permanent shift workers than those on permanent day shift.Shift workers complain of difficulty in sleeping or not getting enough sleep particularly when subjected to night shift.

Circadian, environmental, and social habits, in combination reduce the quantity and quality of their day sleep leading to accumulation of sleep debt which in turn accentuates their feelings of sleepiness and fatigue. This increase lay to a greater margin for errors and accidents.

2.8 Major Health Problem associated with CRSD

Lipkin, et al (1998) said that shift workers are more likely to suffer cardiovascular and digestive disorders. Shift workers also experience headaches, muscle pain respiratory infection and general malaise these in turn result in higher rates of absenteeism employee turnover and higher costs associated with recruiting and training replacement employees. Nonetheless, Steeland, and Fine (1998) studied the effects of shift on worker who do not rotate, to determine whether current shift or recent change in shift was a risk factor for ischemic heart disease; they conduct a nested case control study of heart disease death at work within a cohort of 21,000 men.

They found that there was little evidence of any difference in heart disease risk by current shift.

2.8.1Digestive disorders

Shift workers are thought to have an increased chance of having gastrointestinal (GI) complaints including stomach and digestive problems such as peptic ulcers, gastritis, colitis and gastroduodenitis. A US NIOSH study of 900 workers found four health factors related to night work. Constipation was more common in women and digestive problems for men.

Another NIOSH study found that 2400 workers on rotating shift have more digestive problems than non-shift workers (Scott and Ladou, 1990).There are causes for concern in relation to the health of shift workers experiencing GI problems. Aanonsen (1959) found that peptic ulcers incidence is 2.5 times higher in day workers who left work for health problems than in day workers who never performed night shift work. It was observed that digestive problems arising during shift work may not completely disappear even after returning to a normal schedule (Scott and Ladou, 1990).The increase in gastrointestinal complaints is thought to be due to inequality occurring between time of meal and the endogenous circadian rhythm of the GI system (Costa, 1997). In normal day/night oriented people, meal times are constant during the day and occur in phase with the GI endogenous circadian rhythm.

The rhythm is defined by gastric secretions, acidity, motility and absorption; digestive ability is high during the day as compared to low during night. Therefore eating at the wrong time lead to stomach upsets, nausea, peptic ulcers, constipation and these are commonly found in shift workers. The GI symptoms might be accentuated by the type of food that shift workers eat especially during night which often includes fast foods (Costa, 2001). The circadian rhythm of the digestive system acts with the exogenous timing of meal intake; quantity and quality of meals thus increasing the likelihood of GI symptoms amongst shift workers. Alcohol, caffeine does not interfere with the GI systems.

Whereas cigarette smoking, though contribute to high rates of peptic ulcers, haven't shown consistently there definite cause (Scott and Ladou, 1990).

2.8.2 Cardiovascular related problems

Cardiovascular disease (CVD) is found to strike shift workers more than day workers (Âkerstedt, Knutsson, Alfredsson and Theorell, 1984). Myocardial infarction is reported more in shift workers than non shift workers of same gender and age (Alfredsson, Karasek, and Theorell, 1982). A study span over 15 years of paper mill workers in Sweden shows that the risk of contracting ischemic heart disease (IHD) is higher with the increasing time working on shift (Knutsson, Âkerstedt, Jonsson and Orth-Gonner, 1986).

The most important marker of IHD was age but the second main sign was the duration of shift work.Therefore a link exists between shift work and CVD demonstrating an increase in cardiovascular complaints and IHD, an increase in myocardial infarction as well as an increase in risk factors such as hypertension in shift workers (Costa, 1996).

2.8.3 Hypertension

Ohira et al. (2000) showed that there exists a link between exposures to shift work to hypertension which a risk factor to CVD. The researchers studied the consequence of rapidly rotating shift on blood pressure changes. Blood pressure was measured every half hour for 24 hours on the second day of their shift for 27 male shift workers and 26 male day workers in the same company.The results showed that shift workers having a higher systolic blood pressure than day workers mostly during work hours.

The variations in blood pressure were higher for shift workers and the systolic rose meaningfully over time for shift workers. Two possible reasons are suggested for this. The first was an increase in sympathetic nerve activity and the second was the tendency of the shift workers to contain their anger.

But in general workers had higher blood pressure, higher variability in blood pressure, and long term increase in systolic pressure when working on shift confirming the fact that shift work presents a risk for cardiovascular problems.

2.8.4 Depression

Previous studies have shown a number of mental health problems to be related to the work environment and long hours. However, most emphasis has been on the job strain, with little attention paid to number of working hours. Of the sample aged 25 to 54 who worked 35 or more hours per week throughout 1994/95, 5%of women and 3% of men (Statistics Canada) were classified as having experienced a new major depressive episode at some time in the 12 months before their interview.

Women who worked long hours had 2.2 times the odds of reporting having experienced a major depressive episode, compared with those who worked standard hours. High job strain was related to depression for both sexes.

2.8.4.1 Antidepressive Effect of Sleep Loss and Depression

There is however little information suggesting an impact of shift work on psychopathology such as depression (Cole, Loving, and Kripke, 1990). Other studies on the other hand like that of Skipper, Jung, and Coffey (1990) obtained results of a questionnaire based study among 463 female nurses working either permanent shift or rotating shifts. The result indicated no meaningful relationship between depression and shift work. Moreover Goodrich and Weaver (1998) studied the mental health state of 56 workers and the results were that the degree of depression was not higher for shift workers than day workers.Health effects of sleep deprivation are, however, not always unrelated. Medical involvement prescribing sleep deprivation as a voluntary measure has been proved as an antidepressant technique for some time.

Naitoh et al., (1990) believes that total sleep deprivation gives more relief from depression in depressed patients. It is performed by repeating a single night of total sleep absence for several weeks. It is believed that sleep deprivation helps in resynchronisation of disordered circadian rhythms and re-entrainment of the circadian rhythm.A survey was carried out in 11 hospital in Japan, a sample of 620 nurses with average age 24 were taken.

A questionnaire was designed containing items such as sleep disorders, work performance and shift work related problems. The results shows a high significant association of nurses using alcoholic drinks to induce sleep.(Ohida, et.al, 2001).

2.8.5 Fatigue

In the absence of a scientific definition:"... Fatigue, or rather mental fatigue, may perhaps be considered to be a syndrome whose symptoms include, amongst other elements, subjective tiredness and a slowing of normal cognitive function." (Rogers, Spencer and Stone ,1999)They also conceptualize fatigue as a continuum with differing levels of fatigue (or tiredness) and alertness. There is also physiological fatigue, resulting from lengthened bodily work, for example muscular fatigue.Another Japanese article (Shimonitsu and Levi, 1992) reported that the number of weekly working hours in Japan was increasing, with almost one quarter of male workers doing at least 60 hours of work per week.

They reported that two thirds of Japanese workers complained of physical or mental fatigue, with around half carrying fatigue over into the next day at work. They also note that studies that have looked at overtime have found links with fatigue and health-related outcomes such as 'karoshi' - 'death from overwork'.

2.8.5.1 Long hours of work versus fatigue?

Fatigue is the result of putting in effort (working) for long hours without sufficient rest. Konz (1998) asserts that the purpose of resting time is to overcome fatigue, and that fatigue increases exponentially with time. This kind of concept was the focus of a study conducted by Van der Hulst and Geurts (2001).

Researchers used the Effort-Recovery Model as their theoretical perspective (Mejiman and Mulder, 1998, cited in Van der Hulst and Geurts, 2001). This model hypothesizes that any costs associated with effort (i.e., working) will be stabilized if there is sufficient recovery time (either in the working day, or after work). If there not enough time to recover due to long shift, fatigue will accumulate, hence having a negative impact on health.

So, fatigue seems to be the main cause of associated ill health.

3.0 Family and Social life

Interference in social and domestic lifestyle is of key significance of shift work. Shift workers are usually unable to take part in social activities. They are usually working when social activities are planned usually during weekends and they are off during week days when others are at work or at school and this can make commitments very difficult. A part of the time off must be utilised to catch up on sleep loss.

Until they catch up on this sleep debt, shift workers are liable to feel tired and irritable thus reducing the quality of their time off, thus spending less time with their family.Koller, (1996), states that shift-work and night work have implications for the entire living sphere of mankind, thus health hazards and stresses of work itself, as well as intervening factors from outside the working life may influence and impair the state of health. There is an agreement that shift-workers are a population at risk, this is due to the fact that, they are exposed to psychobiological, desynchronisation and reduced coping associated with shift-work. (Folkard et. al. 1985; Costa et. al.1989; ILO. 1986; 1990; Rutenfranz, 1982), describe that these effects are associated with phase shifting in sleep and wakefulness cycles, and cause interferences with daily routine at work and in 27 family and social life.

Frustration, low morale, and diminished job satisfaction are also common among shift-workers (Kogi, 1996).

3.0.1 Family and Social Adjustment in relation to Type of Shift

A review of the effects of shift work on worker family and social integration was performed by Colligan and Rosa (1990). Those on permanent day shift showed more positive outcomes of highest level of satisfaction with only 6% expressing a desire for another different schedule. They also showed highest marital satisfaction, family socialisation, and prevention of domestic friction.Mott et al. (1965) investigated on the fixed afternoon shift workers who reported more sleep and decreased health complaints than fixed night and rotating shift workers.

But however afternoon shift workers expressed most frustration with the amount of time they could offer to their wives and for relaxation. Concern was also expressed for their inability to give protection to their spouses during later stages of their shift. 79% of the workers on afternoon shift felt being restricted to their social and family life than to 7% of those on day shift (Wedderburn 1978).Tasto et al. (1978) found that fixed night shift workers were happier than afternoon or rotating shift workers excluding day shift workers with the quantity of time they had for personal and social activities.As per Colligan and Rosa (1990), rotating shift workers experiences the best as well as the worst advantages of each of the fixed shifts. On day shift, the workers sleep and eat in conformity with day time; free to socialise during evening time but occupied at work during daytime. This situation rules out daytime leisure activities.

Afternoon shift follows normal daytime physiological rhythm and allows for long sleep period but the disadvantage is that it prevents family and social activities taking place during evening time. However at night the worker experiences reduced sleep physiological desynchronisation, but have lot of time for day and evening activities. In relation to social and family demands, rotating work shift can engender unique problems such as family disputes.

3.1 Leisure for shift workers

The type of work schedule can also affect the time allocated to leisure by shift workers. Night shift workers have more time available as compared to other types of shift workers; more time to help their spouses and housework and personal activities than rotating or day shift workers (Mott et al. 1965).

Staines and Pleck (1984) showed that afternoon shift workers have more time than day workers but acknowledged more friction between their work schedule and family requirements. Tasto et al. (1978) reported that afternoon shift workers are unhappy with the quantity of time they have for participating in social gatherings and personal activities than compared to day workers.

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