Night shift

 

Holy Quran said in

 [the News verses]

[11] And made the day as a means of subsistence?

Holy Quran said in

 [the Greeks  verses]

[23] And among His Signs is the sleep that ye take by night and  by day, the quest that ye (make for livelihood) out of His Bounty:

Holy Quran said in

 [the Criterion verses]

[47] And He it is Who makes the Night as a Robe for you, and Sleep as Repose, and makes the Day (as it were) a Resurrection.

Shift work link to heart disease . type 2 diabetes and sleep disorders

A study in Antarctica has supported theories that night shift workers are at increased risk of developing heart disease.

Previous laboratory studies have led to similar conclusions, but this is the first time the link has been shown under real conditions, say researchers from the University of Surrey in Guildford.

The team says their findings could have major significance, as an estimated 20% of the UK workforce, around six million people, does shift work.

Shift work has been found to disrupt circadian rhythms, the daily cycle.

Previous studies have looked at how the stress of night shifts could be linked to increased heart disease risk.

This research examined how the body reacts after a meal, depending on what time of the day it is eaten.

Post-meal checks

Researchers looked at 12 healthy night shift workers aged 24 to 34 years at the British Antarctic Survey station at Halley Bay in Antarctica.

Their hormonal and metabolic responses to meals were measured during daytime on a normal working day, during night time at the beginning of a period of night shift work and during the daytime on return from night working to daytime working.

The workers did a week of normal 0900 to 1700 shifts before changing to a week of midnight to 0800 shifts with no time to adapt, then back again after another seven days.

Blood and urine checks were also carried out.

It was found that after a meal, night shift workers' blood levels of glucose, insulin and triacylglycerol (TAG), a fat which stores energy, were significantly higher than in normal daytime hours.

Fat deposits

Levels of glucose and insulin returned to pre-shift levels two days after returning to daytime working, but TAG levels were still found to be raised.

When TAG levels are high, it is easier for fat deposits to form on the inside of arteries, leading to vascular disease.

Working irregular hours depresses the immune system and makes the body more vulnerable to disease

Workers on such shifts are also more likely to suffer from heart disease , type 2 diabetes and sleep disorder .

Night shift link to heart problem

People who work nights are more prone to a dangerous heart condition - possibly because of the chronic stress caused by their work patterns, research suggests.

Scientists compared employees who worked shifts, including nights with others who worked normal daytime working hours.

They found shift workers were twice as likely to develop an irregular heartbeat.

And they said that could be because they suffer from "chronic stress" because of their work patterns.

The researchers say an irregular heartbeat can be an indicator a person will go on to develop more serious heart problems.

But UK heart experts said such abnormal rhythms were common place, and not necessarily an indication someone would develop coronary heart disease in the long term.

Previous studies have speculated that people working shifts are at an increased risk of heart disease because of disturbance to the circadian rhythm and changes to their behavior.

And research published last year suggested the heart does not respond well to being made to work during the middle of the night, because the body is programmed to slow down during that time.

Comparison

The researchers looked at premature ventricular complexes (PVC), "early heartbeat problems", which occur when an irregular heartbeat occurs earlier than normal.

Doctors from Maastricht University in the Netherlands looked at 42 daytime workers and 83 shift workers who were all new to their jobs.

Their hearts were checked then, and subsequently after a year in the job.

It was found that both day and shift workers had slightly unfavorable changes to their heart rates.

But twice as many shift workers developed PVC compared to the day workers.

The more nights they worked, the more their risk increased.

This was true even when researchers took factors such as smoking, drinking coffee or alcohol, weight, age, sex and job stress into account.

Stress

Writing in the Occupational and Environmental Medicine journal the researchers, led by Dr Ludovic van Amelsvoort, say: "It might be that working at night is a chronic stressor."

They add: "We conclude that the increase in frequency of premature ventricular beats can be regarded as an indicator of unfavorable changes in the myocardial system, and should be regarded as a potentially important factor in the relation between shift work and the increased cardiovascular risk of disease."

A spokesman for the British Heart Foundation said: "There is some evidence to suggest that people who work on night shifts may be more vulnerable to stress.

"This could be attributed to changing sleeping patterns, emotional problems, and family commitments whilst juggling a varying work timetable, sometimes with little social support.

"In this small study the researchers found that those working shifts have an increased number of abnormal heart rhythms.

"In the majority of ectopic heartbeats, where the heart appears to "miss" a beat, it is due to increased emotional stress.

"These abnormal rhythms are common place, and do not necessarily indicate that someone is more likely to develop coronary heart disease in the long term."

Working night shift in bright lights boosts breast cancer risk

  Breast cancer risk increases by eight per cent to 60 per cent for women who work the night shift for many years, according to two studies that suggest the bright light at night diminishes the body's supply of melatonin and increases estrogen levels.

Researchers said the fact that two independent studies, using different methods, found roughly the same results suggest strongly that working the graveyard shift for long periods of time may lower the body's resistance to breast cancer and, perhaps, to other types of cancer.

"We are just beginning to see evidence emerge on the health effects of shift work," said Scott Davis, an epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle and first author of one of the studies. He said more research was needed before a compelling case could be made to change night work schedules, however.

"The numbers in our study are small, but they are statistically significant," said Francine Laden, a researcher at Brigham & Women's Hospital in Boston and co-author of the second study.

Both studies appear Wednesday in the Journal of the National Cancer Institute.

"These studies are fascinating and provocative," said Larry Norton of the Memorial Sloan-Kettering Cancer Center in New York. "Both studies have to be respected."

But Norton said the findings only "hint" at an effect on breast cancer rates from nighttime work and "raises questions that must be addressed with more research."

In Davis' study, researchers explored the work history of 763 women with breast cancer and 741 women without the disease.

They found that women who regularly worked night shifts for three years or less were about 40 per cent more likely to have breast cancer than women who did not work such shifts. For women who worked at night for more than three years, the relative risks went up to 60 per cent.

The Brigham & Women's study, by Laden and her colleagues, found only a "moderately increased risk of breast cancer after extended periods of working rotating night shifts."

The study was based on the medical and work histories of more than 78,000 nurses from 1988 through May 1998. It found that nurses who worked rotating night shifts at least three times a month for one to 29 years were about eight per cent more likely to develop breast cancer. For those who worked the shifts for more than 30 years, the relative risk of breast cancer went up by 36 per cent.

American women have a 12.5 per cent lifetime risk of developing breast cancer, according to the American Cancer Society. Laden said her study means that the lifetime risk of breast cancer for longtime shift workers could rise above 16 per cent. There are about 175,000 new cases of breast cancer diagnosed annually in the United States and about 43,700 deaths. Breast cancer is the second only to lung cancer in causing cancer deaths among women.

In Canada, about 19,500 women are diagnosed with breast cancer each year, and about 5,500 women die from the disease.

Both of the Journal studies suggested that the increased breast cancer risk among shift workers is caused by changes in the body's natural melatonin cycle because of the bright lights during the dark hours.

Melatonin is produced by the pineal gland during the night because melatonin levels typically peak between 1a.m and 2a.m Studies have shown that bright lights reduce the secretion of melatonin. In women, this may lead to an increase in estrogen production and increased estrogen levels have been linked to breast cancer.

"If you exposed someone to bright light at night, the normal rise in melatonin will diminish or disappear altogether," said Davis. "There is evidence that this can increase the production of reproductive hormones, including estrogens."

Davis said changes in melatonin levels in men doing nighttime shift work may increase the risk of some types of male cancer, such as prostate, but he knows of no study that has addressed this specifically.

Both Laden and Davis said the melatonin-estrogen-breast cancer connection is still a theory that will require more research to prove or disprove.

More study is needed to precisely define the risk of shift work and how that compares to other known breast cancer risk factors, such as family history, smoking and obesity, said Singletary. But she said the finding does suggest the need for women who work night shifts to be particularly prudent in following breast cancer screening recommendations calling for regular mammograms and medical exams.

Lack of Sleep Increases Diabetes Risk

A chronic lack of sleep may cause far more serious problems than a tendency to nod off the next day, researchers warn. Their study presented Monday at the American Diabetes Association's annual meeting found that people who do not get enough sleep on a regular basis may become less sensitive to insulin which, over time, can raise the risk of obesity, high blood pressure and diabetes.

In fact, chronic sleep deprivation--6.5 hours or less of sleep a night--had the same effect on insulin resistance as aging, Bryce A. Mander, a research assistant at the University of Chicago in Illinois, and a study author, told Reuters Health. 

"Just like poor diet, sedentary lifestyle, chronic stress and aging, sleep loss is a...risk factor (for type 2 diabetes),'' Mander said.

Type 2 diabetes occurs when the body loses its ability to respond to insulin, the body's key blood sugar-regulating hormone. This insulin resistance causes blood sugar levels to rise, which in turn can increase the risk for a number of serious medical complications including kidney damage, heart disease, blindness and lower limb amputations.

According to the study, led by Dr. Eve Van Cauter, of the University of Chicago, healthy adults who averaged 316 minutes of sleep a night--about 5.2 hours--over 8 consecutive nights secreted 50% more insulin than their more rested counterparts who averaged 477 minutes of sleep a night, or about 8 hours. As a result, "short sleepers'' were 40% less sensitive to insulin. The researchers suggest that sleep deprivation, which is becoming commonplace in industrialized countries, may play a role in the current epidemic of type 2 diabetes. Mander cited a poll by the National Sleep Foundation documenting a steady decline in the number of hours Americans sleep each night. In 1975, the average American slept 7.5 hours, down from 9 hours in 1910. Today, adults sleep about 7 hours a night, he said.

While the findings add to a growing body of research on the role of sleep on human health, further research will focus on the mechanism by which sleep affects glucose regulation and what affect longer sleep will have on short sleepers at risk for diabetes. 

"Basically, one must lead a healthy life in all ways, have a good diet, exercise regularly, minimize stress if possible, but also sleep as much as you can,'' Mander said.