At least one third of cases of delirium could be prevented if better systems of care were in place according to a doctor in today's BMJ.

Delirium - a temporary state of acute confusion - is becoming a major burden on health care services in countries with ageing populations says Professor John Young.

Characterised by fluctuating awareness, confusion and impaired memory, delirium contributes substantially to rates of sickness and death in the population. The condition causes considerable distress to patients and families and it is expensive - Professor Young estimates the cost of treatment can run to an additional £1275 per patient.

It is the most frequent complication of hospital admission for older people and develops in up to half of older patients post-operatively, especially after a hip fracture or vascular surgery. People with delirium are also more likely to develop dementia and vice versa.

According to Professor Young, at the moment, over half of patients with the condition go unrecognised. This could be because diagnosis rests solely on clinical skills. There is no diagnostic test. To improve detection rates he says all clinical encounters with sick older people should routinely include an assessment of cognition.

Professor Young says a number of studies suggest the best way to prevent delirium is to lessen the risk factors for individual patients. He gives, as an example, one study involving medical and hip fracture patients where incidences of delirium typically reduced by one third. The delirium was also often shorter in duration and less severe.

Delirium could be prevented in many cases says Professor Young by improving routine care for frail older people in hospital, as aspects of hospital life are known to significantly aggravate the development of delirium.

He warns that health service practitioners "have yet to systematically tackle the potential for delirium prevention. Few national guidelines have been produced, and delirium remains disproportionately ignored relative to its impact".