Bedsores affect just under half a million people in the UK a year and are mainly found in people who already have an underlying health condition. About one in 20 people who are admitted to hospital with an acute illness will develop a bedsore and people over the age of 70 are particularly at risk because of the ageing of the skin, their reduced blood supply and the fact that the elderly tend to have more mobility problems. Two out of every three cases of bedsores are related to people aged 70 or over.

Though the elderly are the most likely to suffer from bedsores, it is possible to identify other specific groups who are most at risk. They include those who are immobile for any period of time, through injury, illness or sedation. Also, those with long-term spinal cord injuries are vulnerable because they often have reduced sensation so that they do not receive the body's usual signals. Therefore if a patient has a developing bedsore they may not feel it and thus may not change positions, leading to the sore becoming more serious and harder to treat.

The vulnerability of those aged over 70 is exacerbated in those who are very underweight as; naturally, in these cases there will be less padding around their bones. The elderly are also more likely to suffer from poor nutrition which also has an adverse effect on their skin and blood vessel quality, leading to less effective healing. Even where an older person has a good diet and is in good health, their healing from a bedsore is much slower than that of a young person.

The proportion of people in nursing homes who suffer from bedsores is significantly higher than for those in hospital or at home, no doubt due to the fact that those in nursing homes tend to be the most infirm and the most immobile. Other groups of people at a greater risk of developing bedsores are those in a coma for reasons which are obvious, they are immobile and, while unconscious are unable to acknowledge pain. Also, there are some diseases, as well as spinal cord injuries already identified, where a patient's perception of pain is reduced and they are more likely to spend long periods in the same position, so they may not be aware that a pressure ulcer is developing. Also, people in hospital often lose weight because of their condition, especially if they find it difficult to move.

Incontinence is a well-known aggravating feature in terms of bedsores as it inevitably leads to permanently moist skin which in turn results in a greater risk of skin breakdown. Other ailments such as diabetes and some vascular diseases may also affect the blood flow to certain tissues and cause tissue damage. Smokers are also at a greater risk than non-smokers because nicotine harms circulation and smoking also reduces the amount of oxygen in the blood which has a knock-on effect on healing.