Shifting strands

Shifting strands
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First Published: Tue, Jun 19 2007. 12 12 AM IST
Updated: Tue, Jun 19 2007. 12 12 AM IST
Angry mothers and grandmothers, who’ve always insisted that you study during the day and sleep at night, now stand vindicated by science. A recent study published in the peer-reviewed Current Science journal reports that working in shifts adversely affects human longevity.
That’s bad news for a rapidly urbanizing India. While business process outsourcing (BPO) units may be the most visible face of shift work in the booming Indian economy, media and the manufacturing sectors also rely heavily on it. The latest Economic Survey and software lobby Nasscom say that these sectors account for nearly 4.7 million workers.
Pages of medical literature and thousands of conference-hours have been spent debating the effect of shift work on human health. “The most common effects are an increase in ischaemic heart disease (IHD) and peptic ulcers,” said Vincent George, a cardiologist at the All India Institute of Medical Sciences (AIIMS) in New Delhi. IHD, George explains, is considered to be the most common heart disease in developed countries.
A 2001 study in Current Science also pointed out that shift work leads to sleep-related problems, retards performance and increases the probability of accidents at work. “However, the source of all these problems,” said Atanu Kumar Pati, the lead author of the recent paper in the journal, “was that shift work significantly affected the circadian rhythm.”
Circadian rhythmicity, or the biological clock, is best explained using one of Pink Floyd’s most popular songs, Time. This special-effects heavy composition begins with an array of clocks, all ticking at different speeds, but generating an overall harmony. “From day-night cycles to menstrual cycles, there are many of these ups and downs in the body that indirectly contribute to a regular heartbeat,” says Sharad Saxena, a biologist with the Indian Council of Medical Research, “and the body’s constant challenge is to keep these synchronized.”
And these clocks are not restricted to the human body. In 1700, a French scientist named Jean-Jacques d’Ortus de Mairan experimentally showed that leaves moved in certain patterns every 24 hours, irrespective of sunlight or any other movement, proving that there were internal processes which regulated rhythms within living beings. Though de Mairan gained more fame as an astronomer and has a lunar crater named after him, he indirectly kicked off a whole branch of science called chronobiology. As of today, research has shown various kinds of body clocks that are maintained by the DNA in organisms ranging from fungi to bacteria and human beings. “Chronobiology is modern medicine’s acceptance of the importance of biorhythmic cycles in the body. However, treatment in the Ayurveda system has traditionally involved identifying and correcting, discordant biorhythms,” said Radha Yegnanarayan, head of the pharmacology department at the University of Lucknow, who is on the board of the Indian Society of Chronobiology (ISC). The ISC is a group of researchers that focuses on alternative medicine, and unconventional approaches to therapy.
Melvyn D’souza, a 24-year-old call centre employee at Gurgaon, says he, as well as his employers, are completely satisfied with his performance, even though he’s been doing the graveyard shift (12-8am) for over a year. “I’ve anyway always been a night owl but many colleagues, when they joined, complained of sleep related adjustment problems,” says D’souza.
Scientists say that a chemical called melatonin (its secretion is influenced by sunlight), which regulates sleep cycles within the body, is most affected by working in shifts. “Even patients on steroids should take medicines in the morning,” says Prof. Yegnanarayan, “as taking it in the evening interferes with the melatonin secretion.” But Upendra Kaul, veteran cardiologist at the Fortis Group of Hospitals, New Delhi, says the surrounding social environment was the biggest enemy of shift workers. “Graveyard shift workers come home in the morning, when other family members are getting ready to work. Even when they sleep, there are constant disturbances relating to day activity, all of which disturbs body rhythms.” He said these disturbances gradually take a toll on the human body.
This is proved by Pati’s study. Here, the birth and death dates of 282 day workers and 312 shift workers at the Nagpur railway station were compared, along with the reasons for the deaths. The researchers concluded that total longevity among shift workers was reduced by almost four years. That’s the kind of reduction you get if you smoke 40 cigarettes a day for 30 years, assuming a single cigarette takes five minutes off your life, which is what current medical literature says. Dr Kaul’s views on the “social environment”, seems aligned with that of Roberto Rafinetti, a professor of psychology at the University of South Carolina in the US.
In an email interview, Prof. Rafinetti said conditions such as jet lag result from an abrupt change in the “world clock” (or the outside clock) that is not immediately followed by a corresponding change in the internal clock.
“There is a lot of ongoing research looking at potential mechanisms to resynchronize the internal clock. Although properly timed physical exercise and properly timed ingestion of the hormone melatonin are candidates, the only well- established mechanism is properly timed exposure to bright light,” he said. After a few days of exposure to the new light-dark cycle, almost everyone resynchronizes to the new cycle.
In order to speed up the re-synchronization, exposure to artificial bright light (and avoidance of natural sunlight) must be planned for the day of the trip. The exact times depend on various time zones and individual characteristics.
An emerging method to deal with disturbances caused by shift work is phototherapy. “It’s relatively new in India,” said Sushma Kaul, professor at AIIMS, “but rather popular in the West.”
According to her, physicians have been using phototherapy to treat sleep disorders. Also, phototherapy is now a standard procedure in the treatment of a mood disorder—seasonal affective disorder. The light intensity must be high (sunlight or very bright artificial light), and the timing is very important. If you wake up too early, you will need exposure to bright light in the evening. If, instead, you have problems falling asleep (and then wake up late), you will need light exposure in the early morning (that is, soon after you wake up). By gradually advancing or delaying the time of light exposure, you can gradually reset your internal clock to the desired time.
The mammalian body clock was thought to be set exclusively by a part of the hypothalamus in the brain called the suprachiasmatic nucleus (SCN). Recently, Henryk Urbanski and his colleagues at the Oregon National Primate Research Center in Beaverton in the US, have discovered a second clock—in the adrenal glands. Urbanski and his team discovered rhythmic 24-hour fluctuations in gene activity in at least 322 genes in the adrenal glands of macaques, including six vital ones for clock activity in the SCN. Urbanski says the adrenal clock probably plays a key role in releasing mood-altering hormones at key times. The stress hormone cortisol, for example, usually peaks in the morning to provide vigour, and troughs in the evening to promote sleepiness. Urbanski says that the SCN is probably the master clock, because it receives information on light levels directly from the retina.
“We don’t know how the adrenal clock is being synchronized with the environment,” Urbanski adds. The discovery could yield better treatments for jet lag.
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First Published: Tue, Jun 19 2007. 12 12 AM IST
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