Routine Screening of Patients for Malnutrition Decreases Risk of Mortality

Malnutrition is a significant health burden within the elderly population, yet is often side-lined due to the global obesity epidemic. By 2040 it is estimated that 1 in 7 people in the UK will be aged over 75 years [1] therefore its prevalence is only likely to increase. A recent study by Söderström et al. stated that malnutrition increases risk of morbidity and mortality within older adults [2]. Conducting wider research into this association and possible methods of nutritional assessment it has been concluded that screening of hospital admissions should be a high priority to ensure individualised nutritional care plans can be implemented as early as possible to improve disease outcomes.

It is estimated that one third of over 65s in the UK are suffering from, or at risk of, malnutrition when admitted to hospital [3], with this figure predicted to rise as the population ages [4]. Malnutrition is defined as “a state in which a deficiency of nutrients such as energy, protein, vitamins or minerals results in measurable adverse effects on body composition, function and or clinical outcome” [5] and is therefore associated with increased morbidity and mortality due to a greater vulnerability to infections and clinical complications [6].

A number of factors cause undernutrition within the elderly including reduced mobility, affecting shopping and meal preparation, dementia, leading to self-neglect, and a decreased sensory threshold, reducing appetite [7]. A downward health spiral can exist where reduced dietary intake and decreased physical activity causes the loss of muscle strength, impairment of the immune system and diminished cognitive performance, which in turn significantly affect nutritional behaviour [8]. 

Reduction in body weight is considered to be the most important indicator of malnutrition [8], as seen by a low BMI and unintentional weight loss of 5-10% over a period of 3-6 months [9]. Consequently, diagnosing malnutrition commonly involves taking anthropometric measurements. However, one of a number of validated screening tools are frequently used to assess a variety of domains such as functional status, lifestyle, diet and subjective health [8], allowing for cause and future risk of malnutrition to be evaluated.

The mini nutritional assessment (MNA) is an instrument recommended by a number of organisations including the American Dietetic Association (ADA) and the European Society for Parenteral and Enteral Nutrition (ESPEN) for use within those aged over 65 years [10]. In the study conducted by Söderström et al. this method was employed to measure nutritional risk within a cohort of hospital admissions aged ≥65 years to determine whether malnutrition was associated with risk of mortality from a number of specific causes [2]. This review will compare the conclusions obtained with those from wider research to discuss the importance of the NICE quality standard that states malnutrition screening should be mandatory for individuals within care settings [5].

Method

Study population

1771 hospital admissions were initially included in the study, with 1767 patients followed up after a median of 5.1 years.

Baseline data collection and nutritional screening

Clinical characteristics data was obtained at baseline including independence of living. Primary and secondary medical diagnoses were collected at patient discharge and categorised into twenty diagnosis groups of the ICD-10. Anthropometric measurements were taken and nutritional screening using the full 18-item MNA instrument was performed on all patients, categorising them as well-nourished, at risk of malnutrition, or malnourished.

Data collection at follow-up

Cause of mortality data was obtained from the Swedish Cause of Death Register and coded according to ICD-10. All causes of death stated on the death certificate were included. 20 main diagnostic groups were identified based on ≥50 deaths within each.

Statistical analysis

Survival analysis considered time from date of MNA assessment to cause-specific death or date of censoring, which included emigration, end of follow-up or death from other causes. The association between nutritional status and risk of death was analysed using Cox proportional hazards regression for each diagnostic group, with cause-specific death as the outcome in each. All models were adjusted for a baseline characteristics and diagnosis.

Results

Subject characteristics at baseline

Of the 1767 patients followed-up, 35.5% were well-nourished, 55.1% were at risk of malnutrition and 9.4% were malnourished upon hospital admission. The mean age of participants was 78.1 at baseline. 95.1% of subjects lived at home at the start of the study.

Subject characteristics at follow-up

At follow-up, 928 participants were alive and 839 deceased. Mean age at death was 82.8. 53.4% of patients died in hospital, 26.0% in a nursing home and only 9.6% died at home. The most common causes of death were those of the circulatory system (62.6%), which included heart failure, ischaemic heart disease and cerebrovascular disease, followed by neoplasms (35.9%). 

Results of statistical analysis

For all registered causes of death, nutritional screening group at baseline was related to survival rate. After adjustment, there was a significant association between malnutrition or risk of malnutrition and death from 17 out of 20 of the examined causes. Of the main diagnostic groups there was a significant association between both malnutrition and risk of malnutrition and death from neoplasms, mental or behavioural disorders, diseases of the nervous system, diseases of the circulatory system, and diseases of the respiratory system. 

Discussion

The study by Söderström et al. concluded that poor nutritional status increases risk of mortality [2]. Previous research into cause-specific death is sparse but positive associations between malnutrition and length of hospital stay, morbidity and mortality have frequently been reported. For example, Charlton et al. suggested that length of stay was 18.5 days longer for malnourished compared to well-nourished individuals [11], which may result from delayed wound healing post-surgery as a consequence of decreased fibroblast proliferation and collagen formation [12], and immune system suppression causing susceptibility to complications and nosocomial infections [13].

Moreover, it has been found that a 4-5% loss in body weight over 1 year or a 10% loss over 5-10 years is associated with increased mortality [14] and that malnourished patients ≥75 years may have a 3-fold higher death rate than well-nourished peers [15]. It could be thought that these individuals have a greater risk of mortality than older adults aged <75 years, however it cannot be taken as a definite conclusion due to the correlation between nutritional deterioration and functional limitation [16]. Although this factor is influenced by the progressive decline in muscle mass, which occurs with age [14], the extent of individual independence could be deemed more significant. This means those with cognitive impairment may instead be at highest risk [17].

Söderström et al. studied death within a 5-year follow up period, assessing nutritional risk at baseline [8]. It has previously been found that elderly individuals at high initial nutritional risk experience a decrease in quality of life during follow-up [18], most likely as a result of the physical and psychological effects of functional impairment [19] from sarcopenia, which is often presented in parallel with malnutrition [14], or from the symptoms of chronic disease. In addition, it has been suggested that malnourished patients may be twice as likely to be discharged to a nursing institution [20], reflecting a significant reduction in independence. These findings are important when considering the downward health spiral of malnutrition [8] and the corresponding amplification of mortality risk. 

The MNA was used to measure nutritional status [2], an instrument that acts as a global assessment tool by identifying any need for higher standards of care due to physical or cognitive impairment [21], as well as malnutrition. As a result of this, and its frequent association with disease outcomes, the MNA and similar nutritional screening tools are considered superior to other methods. It has been indicated in numerous studies that anthropometric data such as BMI underestimates malnutrition [22] and does not predict mortality [23] or risk of complications [24]. This is of particular concern when considering obese patients or those suffering body water fluctuations in response to disease [25] as a malnourished state may not be recognised. Moreover, serum albumin is regularly considered a marker of malnutrition. Low serum albumin has been observed to correlate with increased risk of mortality and longer length of hospital stay [26]. Nonetheless, it is not a direct nutritional parameter and its role as an acute-phase reactant links it to inflammatory status, meaning during illness concentration is often decreased and over-diagnosis of malnutrition may occur [27].

Impacts

The literature offers conclusive results regarding the association between malnutrition and disease outcome, although it remains uncertain whether malnutrition came secondary to disease as oppose to increasing risk. This is questioned as symptoms may reduce appetite, medication may cause malabsorption and cachexia can cause loss of lean body mass (8). Regardless of the cause, the ability to identify those suffering from, or at risk of, malnutrition relies on assessment of nutritional status, with validated instruments offering greater accuracy than clinical judgement [28]. It should therefore be recommended that all patients are screened upon admission to hospital. Conducting this assessment within the first 24 hours would allow for early nutritional intervention and personalised care such as prescription of calorie or protein supplements in an effort to improve outcomes such as likelihood of readmission, length of stay and risk of mortality [26][29][30][31].

To maximise implementation, the method of nutritional assessment would need to be quick and easy, non-invasive and cost-effective. Although not used by Söderström et al., a 6-question short form of the MNA (MNA-SF) exists which has been shown to have high sensitivity, although limited specificity [12]. Use of the MNA-SF may therefore overestimate undernutrition, impacting clinical resources, but would highlight individuals who are at risk and may be missed by the full MNA to allow for patients to be monitored to prevent deterioration [12]. Additionally, it could act as an initial screening tool in a 2-step approach, with a full MNA being conducted based on MNA-SF score [18]. It would, however, be imperative to perform additional tests in conjunction with nutritional assessment to identify micronutrient deficiencies as these would not be detected by the MNA [18].

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