Why lack of sleep may trigger arthritis - but treating insomnia may improve the condition

Anyone who suffers from it knows that joint pain can have a significant effect on your life, restricting mobility and making it harder to complete even everyday tasks. But it’s not just during the day that it can cause problems — sleep can be affected, too. Persistent, aching pain in the back, hip, arms and legs can lead to disrupted, restless sleep.

Experts say insomnia is common among the ten million arthritis sufferers in Britain, with some estimates suggesting that nearly two in three experience trouble sleeping. However, until recently restless nights were viewed as a secondary and almost inevitable problem for people with arthritis. But now scientists are realising that this problem is a two-way street: not only does joint pain cause sleep loss, but sleep deprivation makes joint pain worse, and can even accelerate joint damage.

Until recently restless nights were viewed as a secondary and almost inevitable problem for people with arthritis

There is growing concern that sleep disturbance exacerbates osteoarthritis (wear-and-tear arthritis) and rheumatoid arthritis (where the immune system attacks the joints), and experts believe that treating insomnia could lead to an improvement in the condition. ‘There’s a correlation between lack of sleep and pain and it’s a vicious circle. Pain induces lack of sleep and lack of sleep induces pain,’ says Professor Alan Silman, medical director of Arthritis Research UK.

Osteoarthritis develops when cartilage that protects the surface of bones becomes damaged and starts to break down. The exact causes remain unknown, but genes, weight and age are all thought to be involved. Much of the pain and swelling is caused by inflammatory molecules in the body travelling to the joint. For reasons that are not fully understood, disrupted sleep leads to increased numbers of these inflammatory markers, which further aggravates sore joints. One of these markers is called interleukin-1 (IL-1), which is made by white blood cells.

 

Osteoarthritis develops when cartilage that protects the surface of bones becomes damaged and starts to break down

One expert thinks IL-1 is the ‘primary trigger’ of osteoarthritis.  Professor Peter Wehling, an orthopaedic surgeon whose Dusseldorf clinic has become a pilgrimage site for sports stars seeking to prolong their careers, says even a limited amount of sleep disruption can cause the immune system to ‘go into overdrive’. It then begins to ‘flood the body with white blood cells in a vain attempt to address exhaustion-related distress’, as he puts it in his book The End Of Pain.

Many of the IL-1 producing white blood cells lodge in the joints and cause ‘discomfort and gradual erosion of cartilage’, he says.  Professor Wehling warns that even one bad night’s sleep can set this in motion.  Professor Silman from Arthritis UK agrees that inflammatory compounds play a role in arthritis. ‘Sleep disturbance can change the body’s natural cycle of hormones as well as possibly adversely affecting the underlying levels of inflammation,’ he says. He agrees that IL-1 is ‘an important player’ in the development of inflammatory arthritis, but says other cytokines — inflammation-causing chemicals — may also be involved.

He adds that some of the symptoms of osteoarthritis, especially in its early stages, may be a direct consequence of inflammation. And while loss of sleep may release damaging inflammatory chemicals, it also means the joints miss out on the healing benefits of sleep. Sleep is the longest time during which the body has low levels of inflammation and opportunity to heal. Around 15 to 25 per cent of it should be deep sleep — this equates to around 1½ to two hours every night. During this time, energy levels are restored and the immune system strengthened.

But it can take up to 45 minutes of sleeping to enter deep sleep — and these deep phases seem to occur only in the first half of the night, for reasons not understood. This means that if someone is tossing and turning they may have very little deep sleep. This not only increases the number of inflammatory markers in the body, but it can also disrupt the workings of hormones vital for joint healing, says Professor Wehling. Perhaps most notably it lowers production of human growth hormone, sometimes called the ‘master hormone’ because it is vital to many processes in the body including tissue repair, weight management and continuing replacement of bone and collagen.

Though human growth hormone is produced in small surges during the day, by far the biggest burst comes 60 to 90 minutes after falling asleep as we enter deep sleep. Inflammation suppresses human growth hormone — and so deep sleep causes levels to surge. But without much deep sleep we may not produce enough growth hormone, speeding the decline of tissue and bone, causing it to become worn in joint areas. Furthermore, weariness makes people more sensitive to pain, and can lead to them becoming even more immobile. Professor Kevin Morgan, director of the Sleep Research Centre at Loughborough University, explains: ‘Moving involuntarily in the night can wake you up with a lightning shaft of pain and a cracking sensation. 'This sleep disruption makes pain worse the next day, and makes a person less inclined to want to move around. However, movement and activity makes joints hurt less.’

Arthritis Research UK is funding a study by King’s College London’s Institute of Psychiatry, which aims to identify and treat the issues preventing patients with rheumatoid arthritis from being physically active and sleeping well. Around 200 people with the disease are taking part in the research, which it is hoped will lead to new techniques to tackle inactivity, sleep disruption and pain. A similar study by the University of Washington in Seattle involving 375 patients with osteoarthritis is also being held and is due to report next year.

It is examining whether targeting pain and sleep problems is more beneficial than a regimen focusing on pain alone. The researchers have hypothesised that the dual approach will have greater long-term benefits for sleep and pain, increase physical activity and lead to a reduction in healthcare costs. Jo Cumming, head of helplines at Arthritis Care, says the charity speaks to 12,000 people a year, and 63 per cent say they don’t get a good night’s sleep. ‘It is a huge burden to bear. When GPs are considering medication or joint replacements one of the things they ask patients is whether the pain stops them sleeping,’ she says.

But Professor Morgan argues that previously GPs have considered insomnia as an unfortunate consequence of another health problem, rather than an important health problem in itself. This has led to patients not always receiving the best treatment. ‘You have to put in a lot of work convincing clinicians that sleep problems are not just collateral damage from the main disease,’ he says. So what can help those with joint pain achieve a good night’s sleep? Tips include cutting out afternoon naps, using lamps rather than ceiling lights in the evening, avoiding caffeine after 3pm and not drinking alcohol after 9pm. Professor Wehling also recommends ‘keeping a consistent bedtime and rising within an hour of sunrise’. Avoiding midnight snacks can also help. An estimated 50 per cent of our body weight is carried by the menisci, small pads of cartilage in the knee, so piling on the pounds adds substantially to an already considerable strain. Excess body fat can also heighten arthritis directly because our fat cells expand and produce more cytokines, which fuel inflammation.

However, a lack of sleep can lead to weight gain, which is known to make joint pain worse. Levels of melatonin, the key hormone in regulating our daily body cycle or circadian rhythm, are also disturbed by sleep loss, and this in turn upsets the balance of two other hormones. The first is ghrelin, known as the ‘hunger hormone’.  Elevated levels of ghrelin at night can prompt people to raid the kitchen, craving carbohydrates in particular. It also causes extra insulin production, making the body store more fat. The second is leptin, which usually helps regulate appetite, but may be disrupted by loss of sleep.  Studies in mice also suggest that leptin may itself have inflammatory effects.

Source: Daily Mail UK 

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