Sleeping badly can make you feel wretched the next day - but new research suggests it may also have serious health implications later in life. A US study has found that poor sleep may be linked to the creation of deposits in the brain that are a precursor to Alzheimer\'s disease, the most common form of dementia. It seems there are plenty of people on the edge of that minefield. In a recent survey for Ikea, 70 per cent of those questioned said they didn\'t feel they got enough sleep. There are likely to be many reasons for the association between sleep and good health - but one thing is clear: people who sleep badly tend to have compromised immune systems, says Professor Kevin Morgan, director of the Clinical Sleep Research Unit at Loughborough University in the UK. Dr Mazin Aljabiri, general physician and gastroenterologist at EHL Dubai Mall Medical Centre, agrees. \"Poor quality and inadequate quantity of sleep will affect your immunity levels and your ability to perform daily tasks to the best of your ability,\'\' he says. Various studies have also suggested a link between lack of sleep and increased blood pressure, inflammation, the risk of heart conditions, cancer and diabetes. A Harvard Medical School study last year found that men in the study getting the least sleep were at 83 per cent greater risk of having high blood pressure, which can lead to heart disease and stroke, compared to those getting the most sleep. Professor Morgan cautiously adds there \"may be\" a link between lack of sleep and these conditions, although he says more research is needed before this can be confirmed. \"Certainly, there\'s a long-term pay off for not sorting out disordered sleep,\" he says. \"There\'s an unexplained but robust relationship between how long we feel we sleep, and how long we live.\" Research shows that people who estimate they sleep for shorter or longer periods tend to die earlier than those who are in the middle of the spectrum and sleep for an average of just under seven hours a night, explains Kevin. \"There\'s a link between our sleep and our health - I\'d be surprised if there wasn\'t,\" he adds. The latest sleep study, from Washington University, examined people aged between 45 and 80 with no memory problems, half of who had a family history of Alzheimer\'s. It was found that around 25 per cent of participants had pre-clinical Alzheimer\'s - evidence of amyloid plaques, a type of protein deposit, in the brain. These plaques, which are thought to cause brain cell damage, form about ten to 15 years before any symptoms of Alzheimer\'s appear. It was found that people who slept badly, either waking up very frequently or spending a lot of time in bed awake, had a higher chance of having plaques. The study\'s author, Dr Yo-El Ju, a Washington University neurology professor, says, \"It\'s possible that poor sleep quality over the years increases the chance of getting amyloid plaques, but it\'s also possible that having amyloid plaques leads to poor sleep quality.\" She says it will take years of additional research to understand the relationship fully, but in the meantime stresses the importance of making an effort to sleep well. \"I think everyone, not just people who have a family history of Alzheimer\'s disease, should put a high priority on their sleep,\" she says. Professor Morgan agrees that focusing on good quality sleep is beneficial. \"People understand things about diet and exercise, but the third great pillar of our well-being is our sleep, and people know almost nothing about it,\" he says. \"We still hold on to ideas that are utterly nonsensical.\" One such idea, he says, is that we need eight hours sleep a night. Actually, the average amount of sleep we need per night is around seven hours, he says. But how much sleep each person needs differs widely. \"If you\'re wondering how much sleep you should get, the answer is: enough sleep for you to awake refreshed and face the following day efficient enough to do everything you feel you ought to,\" Professor Morgan says. \"If the amount you need to achieve that is three hours, fine. If it\'s seven or nine hours, fine. The answer is not a number.\" As Dr Aljabiri, says: \"The quality of sleep is as important as the quantity.\'\' He explains that many factors affect the quality of our sleep - stress, eating the wrong kinds of food or drink. He explains that it\'s good to have a short nap, of no more than 40 minutes in the early afternoon \"to recharge the batteries\". This is especially beneficial for people over the age of 40, he says. Dr Aljabiri says that going for a short jog or exercising with light weights for about 30-40 minutes before bed can help you sleep better. But Dr Ju warns that strenuous exercise right before bed could keep you awake. However, one point she stresses is to go easy on heavy and fat-rich foods for dinner. Eating a heavy meal before you retire for the night causes blood to rush to the stomach to aid digestion when it should actually be going to the brain to soothe and calm it. She also suggests drinking fewer liquids late in the evening as it could mean visiting the bathroom, which will disrupt your sleep.