Why shift work is linked to so many health problems such as cancer and diabetes: Study finds it damages 1,500 genes

Overinterpreted data.  Study showed that some genes have a circadian rhythm, nothing more

Shift work could damage almost 1,500 genes - explaining why it has been linked to a range of health problems, a study shows.

Disruption to the timing of sleep - also caused by jet lag - is feared to increase the risk of breast cancer, heart disease, diabetes and other life-threatening illnesses.

The researchers found disrupting the body’s natural 24 hour cycle disturbed the rhythm of genes.

To assess the effect on the body of this disruption, researchers placed 22 participants on a 28-hour day schedule without a natural light-dark cycle.

As a result their sleep-wake cycle was delayed by four hours each day until they were sleeping 12 hours out of sync with a normal day.

Blood samples showed that after this experiment the volunteers had a six-fold reduction in the number of genes that displayed a ‘circadian rhythm’ - a rhythm with an approximately 24 hour period.

Professor Derk-Jan Dijk, of the Sleep Research Centre at the University of Surrey, said: ‘We have found about six per cent of genes have a circadian rhythm - this means their activity is higher at certain times of the day than others.

‘We think those triggered mainly by day could be concerned with the immune function and those at night are involved in regulating other genes.

‘The study has important implications because we now need to discover why these rhythms exist and think about the consequences of that.

‘If we put people through these protocols we are influencing very basic processes deep down which could explain why shift work has been implicated in increasing the risk of a range of health problems.’

The human body is believed to have about 24,000 genes - suggesting more than 1,400 could be vulnerable to a change in sleeping habits.

Professor Dijk said all the participants were in their 20s and the study was carried out in very carefully controlled lab conditions.

He said: ‘It would be nice to involve more people but you can see why this would be quite difficult. We were taking blood samples round the clock. It’s a trade-off.’

He hopes his findings, published in Proceedings of the National Academy of Sciences, will be a ‘stepping stone’ to larger studies in the future.

Professor Dijk said: ‘By disrupting sleep - and eating patterns - we are changing molecular processes by causing disturbances in the rhythm of genes.

‘This research may help us understand the negative health outcomes associated with shift work, jet lag and other conditions in which the rhythms of our genes are disrupted.

‘The results also imply sleep-wake schedules can be used to influence rhythmicity in many biological processes which may be very relevant for conditions in which our body clocks are altered such as in ageing.’

Doctors have been worried for years that our 24/7 culture could have unintended consequences for human health with more than four million people – 17 per cent of employees - in the UK now working shifts.

One study showed night shifts triple the risk of heart disease while mental health problems, cancer, depression, diabetes, obesity and strokes have also been linked to poor sleeping habits.

Study co-author Dr Simon Archer said: ‘Over 97 per cent of rhythmic genes become out of sync with mistimed sleep which really explains why we feel so bad during jet lag or if we have to work irregular shifts.’

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Fish oil could help prevent Alzheimer's and also give you a bigger brain

Class effect probably.  The fish eaters were more middle class

Eating more fish could give you a bigger brain - and greater protection against diseases such as Alzheimer’s, claim researchers.

They found people with higher levels of the omega-3 fatty acids found in fish oil may also have larger brain volumes in old age.

This would be the equivalent to preserving one to two years of brain health, says a new study published in the journal Neurology.

Shrinking brain volume is a sign of Alzheimer’s disease as well as normal aging.

Britons are currently advised to eat fish at least twice a week, including one portion of oily fish.

One of the key omega-3 fatty acids is docosahexaenoic acid (DHA), which is thought to help nerve cells communicate with each other.   The richest source of the nutrient is oily fish, such as herring, mackerel and sardines.

For the US study, levels of omega-3 fatty acids including DHA in red blood cells were tested in 1,111 women who were part of the Women’s Health Initiative Memory Study. Eight years later, when the women were aged around 78, MRI scans were taken to measure their brain volume.

Those with higher levels of omega-3s had larger total brain volumes eight years later.

Those with twice as high levels of fatty acids (7.5 vs. 3.4 per cent) had a 0.7 per cent larger brain volume, with the increase measuring up to two inches (6cm).

Study author James Pottala, of the University of South Dakota in Sioux Falls and Health Diagnostic Laboratory Inc. in Richmond, Virginia, said lower levels of fatty acids were linked to smaller-sized brains.

He said: ‘These higher levels of fatty acids can be achieved through diet and the use of supplements, and the results suggest that the effect on brain volume is the equivalent of delaying the normal loss of brain cells that comes with aging by one to two years.’

Those with higher levels of omega-3s also had a 2.7 per cent larger volume in the hippocampus area, the brain’s key memory centre.

In Alzheimer’s disease, the hippocampus begins to shrink even before symptoms appear.

Dr Pottala said: ‘Our study suggests that a higher tissue reserve of omega-3 fatty acids may slow the loss of cognitive function that can accompany brain atrophy.

‘It adds to growing literature suggesting that higher omega-3 tissue levels, which can be achieved by dietary changes, may hold promise for delaying cognitive ageing and/or dementia.’ The best dietary source of omega 3 fatty acids is oily fish because the human body cannot produce omega-3 fatty acids.

White fish is also a healthy food including cod, haddock and plaice although it contains lower levels of essential fatty acids.

Dr Laura Phipps of Alzheimer’s Research UK charity, said: ‘There has been mixed evidence as to the benefits of omega-3 fish oils on the brain and whether they may protect against memory decline and dementia.

‘This study suggests that higher levels of omega-3 fatty acids in blood are linked to larger brain size but the possible reasons for this association need further investigation. ‘We know that the brain gets smaller in people with dementia, but it is unclear from the study what effect larger brain size would have on memory and thinking in the volunteers or their long-term risk of developing dementia.

‘The best way to assess whether omega-3 could protect against dementia is through clinical trials and so far, trials of omega-3 supplementation have not shown benefits in protecting against cognitive decline.’

Dr Doug Brown of the Alzheimer’s Society, said: ‘It’s interesting to see that eating more fish could lead to larger brain volume, particularly in the hippocampus - an area of the brain that comes under attack in dementia.

‘We know that brain shrinkage can be linked to dementia and larger brain volumes could indicate a better ability to cope with the ravages of the condition, but it’s a big leap to draw this conclusion.

‘Whilst interesting, this study still leaves us in the dark about what effect eating fish has on the development of dementia.’

SOURCE