islamabad - A new study suggests the ability to cope with shift work may be down to genetics.

For their study, the researchers analyzed the genomes of shift workers who were part of the Health 2000 Survey - a nationally representative survey conducted between 2000-2011, involving more than 8,000 individuals aged 30 and older residing in mainland Finland. Shift work is becoming an increasing part of the working patterns of Americans, but some people deal with these irregular schedules better than others.

As part of the survey, respondents were required to report their experiences of job-related exhaustion and fatigue.

From their analysis, Prof Paunio and team discovered a variation near the melatonin receptor 1A (MTNR1A) gene that was more common among shift works who reported exhaustion relating to their job.

Further investigation revealed that the variation near the MTNR1A gene is likely associated with a reduction in the number of melatonin receptors, caused by changes to DNA methylation that weaken MTNR1A gene expression.

Melatonin is a hormone that is released into the blood in response to darkness, telling us when it is time to sleep. A reduction in the number of melatonin receptors leads to a decrease in melatonin signaling, which disrupts the circadian rhythm.

As such, the researchers hypothesize that the MTNR1A gene variation uncovered in their study may partly explain why some shift workers find it difficult to cope with an irregular work schedule.

The authors said that”These findings suggest that a variant near MTNR1A may be associated with job-related exhaustion in shift workers. The risk variant may exert its effect via epigenetic mechanisms, potentially leading to reduced melatonin signaling in the brain. These results could indicate a link between melatonin signaling, a key circadian regulatory mechanism, and tolerance to shift work.”

However, Prof. Paunio offers a word of caution when interpreting the findings.

“The variant we have now discovered can only explain a small part of the variation between individuals, and it cannot be used as a basis to determine a person’s tolerance to shift work,” she says.

Toxins in fish impact immune


Fish has always been considered as a highly beneficial food item but thanks to environmental pollution we are going to lose the benefits of eating fish. Toxins in fish harm us badly.

A new study warns that the environmental pollutants found in fish can hamper the human body’s natural defense system i.e. immune system to flush out the harmful toxins.

The study observed 10 persistent organic pollutants (POPs) including the pesticide DDT and industrial chemicals such as flame retardants, present in yellowfin tuna, human blood and urine. All these pollutants were discovered to impact the effectiveness of a key protein in humans and animals, P-gp which flushes out the foreign chemicals from the body.

“When we eat contaminated fish, we could be reducing the effectiveness of this critical defense system in our bodies,” said lead author Amro Hamdoun of the Marine Biology Research Division at the Scripps Institution of Oceanography at the University of California, San Diego.

The researchers point out that newborns and fish larvae are two of the most vulnerable populations. Newborns are particularly vulnerable since they are exposed to high concentrations of POPs in breast milk, and have low amounts of the protective P-gp protein.

Fish larvae may be at increased risk since the accumulation of pollutants may slow down the animal’s defense system to combat other marine pollutants, such as oil hydrocarbons encountered at oil spill sites. This information should be used as guideline to evaluate the health risks faced by mankind from eating contaminated seafood. This suggestion has been given by the researchers at the University of California.

Meanwhile, young kids who miss daytime nap and also stay up late at night are likely to consume more calories, suggests new research. These findings may shed light on how sleep loss can increase weight gain and why a number of studies show that preschoolers who do not get enough sleep are more likely to be obese as a child and later in life.

“To our knowledge, this is the first published study to experimentally measure the effects of sleep loss on food consumption in preschool children,” said study first author Elsa Mullins from University of Colorado Boulder in the US.

“Our results are consistent with those from other studies of adults and adolescents, showing increased caloric intake on days that subjects were sleep deprived,” she said.

In this small study, preschoolers were deprived of roughly three hours of sleep on one day - they had no afternoon nap and were kept up for about two hours past their normal bedtime - before being awakened at their regularly scheduled times the next morning.

During the day of lost sleep, the three- and four-year-olds consumed about 20 per cent more calories than usual, 25 per cent more sugar and 26 per cent more carbohydrates, lead study author Monique LeBourgeois, Assistant Professor at CU Boulder.

The following day, the kids were allowed to sleep as much as they needed. On this “recovery day,” they returned to normal baseline levels of sugar and carbohydrate consumption, but still consumed 14 per cent more calories and 23 per cent more fat than normal. “We found that sleep loss increased the dietary intake of preschoolers on both the day of and the day after restricted sleep,” LeBourgeois said.