As the days are now darker for longer the prospect of another miserable damp and cold winter suddenly becomes a stark reality. Indeed, it’s not until late March that daylight time finally becomes longer than the time we have to spend in darkness.

Although only a minor irritation to some, for many winter has a significant impact upon their health and wellbeing. The reason for this has only relatively recently been understood. As well as enabling us to see, light also has a profound impact upon human physiology. Receptors in the retina of the eye are directly connected to areas of the brain that are integrally involved in hormone production, mood, and the whole area of sleep and wakefulness.

That's all well and good, but it's not like we're existing with candles or a camp fire as our only source of light is it? The advent of electricity in the home and workplace has provided us with some marvellous indoor lighting options, however, these all are solely developed to enable visually directed tasks. The light that is produced by a standard indoor lighting source does not contain enough "short wavelength" light to impact those important areas of the brain that control how we feel and function. As a consequence many of us feel at best "out of sorts", but at worst downright depressed during the winter months.

There's a vocal group of supporters who advocate remaining on British Summer Time all year long and moving away from a near 100 year tradition of tinkering with the clocks twice a year (there were in fact a few years in the 1960s when we stayed on BST throughout the year without turning the clocks back). Without getting into the pros and cons of the respective arguments for and against clock changing, the main issue is actually that we choose to live at northern latitude of more than 50 degrees, and with this comes the inevitable short days in the winter time.

So…what does this all mean to employers and providers of workplace health programmes Well, this is still quite a difficult question to answer. Some researchers have shown a greater incidence of mental health problems, including suicides, during the winter months in those living at northern latitudes, others, however have shown the converse, with a peak of such issues during the summer months, possibly due to "too much" daylight and lack of sleep. Without trying to unpick the possible reasons for these disparities it is clear that changes in light and dark do have a profound effect on how many people feel, perform and also how well they sleep. Surveys have consistently shown that high proportions of western working populations have regular sleep issues. In turn, sleep problems and sleep disturbance has a knock on effect upon stress symptoms and work performance as well as effects upon appetite and blood pressure.

The most common sleep problem reported is insomnia, the definition of which includes difficulty falling asleep, difficulty staying asleep and waking up too early and not being able to get back to sleep. Data from the National Sleep Foundation in America, who conduct an annual survey on sleep problems, suggests that half of all adults experience regular symptoms of insomnia. Some commentators have suggested that this has contributed to the rise in obesity in society. How so, you may ask? Interestingly sleep deprivation alters appetite; it has a subtle effect on our food choices, with tiredness tending to drive a desire for higher fat and higher sugar food types than during times of alertness. In addition, researchers have shown a clear link between total sleep time and obesity; those sleeping for shorter lengths of time have a much higher chance of being obese. An imbalance of two important hormones, leptin and ghrelin, in these individuals appear to stimulate appetite whilst simultaneously decreasing energy expenditure.

It is clear that sleep, wakefulness, appetite and the season can have a profound effect upon individuals. It is also clear that we are a long way from understanding everything we need to know about these interactions. But what we do know is that one of the most important components for individual health and wellbeing is getting regular, good quality sleep.

The fact that so many of the population report regular and unresolved sleep issues is perhaps not surprising when you consider that doctors in training get virtually no instruction on sleep and the treatment of sleep disorders. Couple this with the lack of good quality sleep disorder investigation and treatment centres and you see a real public health issue that is not just an inconvenience, but a threat to both health and productivity. Perhaps it is time for employers to step in with some much needed help?