Malnutrition

In recent years there has been increased public interest around malnutrition. In particular there has been a focus on how many patients enter and leave hospitals in England who are malnourished.

Symptoms and causes of malnutrition

People who are malnourished may experience a range of negative effects on their body as a result of a lack of nutrients in the body. Their symptoms may include one or more of the following:

• Impaired immune response
• Impaired thermoregulation
• Breathing difficulties
• Depression
• Poor libido (sex drive) and fertility problems
• Fatigue.

According to NHS Direct, the three most likely causes of malnutrition in the UK are an inadequate diet, stomach or intestinal conditions, and alcohol dependency.

Inadequate diet

There may be a variety of reasons why someone's diet may be inadequate. For example people may have:

• problems eating or swallowing, eg following a stroke a loss of appetite while suffering depression
eating disorders, such as anorexia nervosa
• difficulty getting to the shops or preparing food due to mobility problems.

Stomach or intestinal conditions

Stomach or intestinal conditions, such as gall stones or stomach ulcers, can make eating painful and can include symptoms such as diarrhoea and vomiting where valuable nutrients for the body can be lost. These conditions can affect the way the body digests food and therefore maybe be unable to absorb the necessary nutrients.

Alcohol dependency

Malnutrition can affect people with alcohol dependency problems as alcohol contains sufficient calories to stop someone feeling hungry, but does not contain other necessary nutrients needed to stay healthy.

What can HES figures tell us about malnutrition?

HES figures can tell us the number of admission and discharge episodes (see the end of this article for definitions) for patients admitted to hospital in England with a diagnosis of malnutrition. They can also provide information on the type of diagnosis; a primary diagnosis (the main condition being treated or investigated) or a secondary diagnosis (a subsidiary illness or condition).

For example, a patient admitted to hospital with a stomach ulcer may not have been able to eat properly; they will have a primary diagnosis indicating a stomach ulcer and could have a secondary diagnosis of malnutrition. When looking at secondary diagnoses though, it is not possible for us to distinguish between patients who were malnourished on admission and those who became malnourished following admission.

Trends over time

The results presented below are a count of admissions and discharges where there was (a) a primary or secondary diagnosis of malnutrition or (b) a primary diagnosis only.

As tables one and two illustrate, the number of hospital admissions and discharges associated with malnutrition has steadily increased. The figure for admissions and discharges where secondary diagnoses of malnutrition are included shows that malnutrition often isn't the main reason why a patient tends to be in hospital.

Since 1998-99 the percentage increase in admission and discharge episodes has increased at a very similar rate when there was a primary or secondary diagnosis of malnutrition; at 143% and 158% respectively. The percentage increase for admissions and discharge is halved when looking at a primary diagnosis of malnutrition alone; at 39% and 41% respectively.

Interpreting HES data on malnutrition

There are several caveats to be aware of when interpreting HES data regarding malnutrition. The following sections outline the most important ones.

Comparing admission and discharge episodes

Despite tables one and two showing that there are a greater number of discharge episodes with a diagnosis of malnutrition than admission episodes, they do not imply that patients are becoming malnourished during their time in hospital and should not be directly compared with one another.

There are several reasons why we would expect there to be more discharge episodes than admission episodes with malnutrition diagnoses. For example:

• patients showing signs of malnutrition often undergo tests to establish the cause of their symptoms. A formal diagnosis can not be made until the results are available, which may be as late as the patient's last episode in a particular hospital (their discharge episode)
• the count of admissions and discharges do not represent the number of inpatients; a person may have more than one admission within the year. It may be that rather than more patients being admitted with malnutrition the same patients are being treated more frequently, such as those suffering from anorexia nervosa
• it is impossible to determine from HES figures whether a secondary illness of malnutrition was acquired before or after a patient was admitted into hospital
• diagnosis of malnutrition in the discharge episode will be the last diagnosis that a particular patient was being treated for. It is not the diagnosis at the moment the patient is discharged as information on the diagnoses that a patient has on leaving hospital is not collected. As such patients who have a discharge episode with a diagnosis of malnutrition does not imply they were still malnourished when discharged from hospital.

Assessing growth over time

HES figures are available from 1989-90 onwards. During the years that these records have been collected by the NHS there have been ongoing improvements in quality and coverage. These improvements in information submitted by the NHS have been particularly marked in the earlier years and need to be borne in mind when analysing time series.

In addition to this, the number of secondary diagnosis fields increased to 19 in 2007-08. Up until this point a patient could only have a total of 13 secondary diagnoses (from 2002-03 to 2006-07) and 6 prior to 2002-03 for their hospital episode. Some of the increase in admissions and discharges relating to malnutrition could therefore be attributable to the fact that doctors were simply able to record more information after 2002-03.

Finally, it is likely that over time doctors have become more aware of the possibility of malnutrition and more sophisticated techniques have evolved to diagnose malnutrition. In February 2006, the National Institute for Health and Clinical Excellence (NICE) published clinical guidelines to help the NHS identify those who are malnourished or at risk of becoming malnourished. See the NICE website for more information. It is also possible that a greater proportion of people who are malnourished are referred to hospital today rather than being treated in the community as in the past.

Definitions

Defining malnutrition

The NHS Classification Service defines malnutrition by the following International Statistical Classification of Diseases and Related Health Problems (ICD-10) codes:

• E40 Kwashiorkor
• E41 Nutritional marasmus
• E42 Marasmic kwashiorkor
• E43 Unspecified severe protein-energy malnutrition
• E44 Protein-energy malnutrition of moderate and mild degree
• E45 Retarded development following protein-energy malnutrition
• E46 Unspecified protein-energy malnutrition
• O25 Malnutrition in pregnancy

The data above does not include diagnoses that are not limited to malnutrition. The ICD-10 category P05.2 - Fetal malnutrition without mention of light or small for gestational age - has also been excluded from our analysis. This is because the diagnosis is only assigned to babies in the first 28 days of birth and is most likely to be the result of poor maternal nutrition and placental insufficiency.

Admission episodes

A patient's admission episode covers diagnoses made on admission. Admissions are defined as the first period of inpatient care under one consultant within one healthcare provider. Please note that admissions do not represent the number of individual patients, as a person may have more than one admission within the year.

Discharge episodes

The discharge episode covers the last diagnosis before the patient is discharged (this includes transfer to another hospital).The period between the last diagnosis before discharge and discharge itself might be a few hours but equally it might be a few months. We simply cannot tell how the patient's diagnoses have changed in that time. An in-year discharge episode counts discharges that end during the data year (1 April - 31 March), irrespective of when they began.