Shift work link to heart disease

The research was carried out on workers in Antarctica

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.

If you're working a rotational shift system, your body clock is probably not adjusting at all

Dr Linda Morgan

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.

Dr Linda Morgan, a reader in nutritional endocrinology who worked on the study, told BBC News Online: "This has a couple of implications.

"If you're working a rotational shift system, your body clock is probably not adjusting at all."

She said it was also important for night shift workers to eat healthily - something shift workers often do not do.