Fibromyalgia is a syndrome (fibromyalgia syndrome, or FMS), or a cluster of problems. People who have fibromyalgia suffer with pain, either all over or in particular places, have sleeping problems, are overwhelmingly tired and may have many other symptoms.

Five to ten per cent of the population has fibromyalgia. Most of them are women, but men and children do experience the symptoms, too.

Pain is the most distinguishing characteristic of fibromyalgia. Medically, it's described as generalized musculoskeletal aches, pain and stiffness. For the pain to be diagnosed as fibromyalgia, it has to be present in all four body quadrants (arms and legs) for at least 3 months, and there has to be pain when pressure is applied to at least 11 of the 18 identified trigger points.

That's the medical description. Here is how people with fibromyalgia describe it.

'I can hardly move because of the pain I'm in. I'm fighting to stay mobile.'

'There is no way to describe the pain. You live with it on a daily basis.'

'What people don't realize is that I am in pain all the time, every day.'

'Sometimes you think, no big deal, it's just pain. It's not life threatening. Sometimes you wish it was. At least there'd be an end in sight.'

The pain waxes and wanes, varying in intensity. People have good days and bad days. Some days it's not too bad; some days it's pretty much disabling. The pain of fibromyalgia often gets worse on cold or humid days, when you haven't slept well, when you are too inactive or too active, when you are stressed or when your hormones change.

The second most disabling characteristic of fibromyalgia is fatigue. Recent findings suggest that the fatigue is due to a stage four sleep disorder called alpha EEG anomaly. During deep stage four sleep, the brain has bursts of awake-like activity, so there is not enough undisturbed deep sleep for the body to get sufficient rest.

In addition to alpha EEG anomaly, many FMS sufferers also have sleep apnea, upper airway resistance syndrome, bruxism (teeth grinding during sleep), limb movement and jerking and restless leg syndrome. All of these contribute to the fatigue of fibromyalgia.

Again, this is how fibromyalgia sufferers describe their fatigue.

'The fatigue is worse than the pain.'

'Some days going to the bathroom feels like a ten-mile hike.'

'On bad days, all I can do is turn on the TV for the kiddies and veg with them.'

Pain and fatigue are the most disabling features of fibromyalgia, but there are other distressing symptoms, too. 40-70 per cent of fibromyalgia sufferers experience irritable bowel syndrome or other gastrointestinal problems. Constipation and diarrhea, abdominal pain, excessive gassiness, nausea and gastroesophageal reflux are common.

Many fibromyalgia sufferers are distressed by associated mental and emotional problems that manifest themselves alongside the physical ailments. Anxiety and depression are common. It's not known whether they are independent factors, or if they are related to living in constant pain and fatigue and the social stigma of fibromyalgia. People also complain of confusion, experiencing difficulty thinking clearly and a reduction in ability to perform mental tasks. This overall mental fogginess has been termed 'fibro fog.'

Other symptoms of fibromyalgia include headaches, restless leg syndrome, skin sensitivity and rashes, dry eyes and mouth, Reynaud's syndrome, and various neurological problems.

Fibromyalgia is an invisible disease. Sufferers look fine on the surface. However, under their outward appearance they are often exhausted and in excruciating pain. Fibromyalgia is a chronic illness that is, at its worst, incredibly disabling. The symptoms have to be managed, and even then the pain and fatigue wax and wane. It's a difficult disease to live with, but it's not hopeless. Medical care and lifestyle management can make a big difference in how you feel if you are suffering from fibromyalgia.