Respiratory Dietician Sarah Airey shares her expertise on the link between Chronic Lung Disease and Malnutrition, and her recommendations for how nutrition can be a vital building block in the care of respiratory patients.
Can you tell us a little bit about the relationship between malnutrition and chronic lung conditions?
Malnutrition is used to describe undernutrition and overnutrition (obesity), both of which are common in chronic lung disease (CLD). The detrimental physiological and psychological effects of malnutrition and the consequences it can have on health outcomes are well established. Nutrition is also a factor in the development of frailty, which has more recently been recognised to have a negative impact on morbidity and mortality.
In people with CLD, malnutrition can increase the potential for subclinical micronutrient deficiencies, influencing immune function and oxidative stress damage in the lungs. Weight loss and sarcopenia impact on exercise capacity and physical function, which are already affected by reduced lung function. Malnutrition has been shown to increase exacerbation rates and the need for hospital admissions. It also increases recovery times and is associated with higher rates of anxiety and depression and, therefore, overall, can significantly reduce quality of life.
As CLD progresses, the risk of developing malnutrition increases, likely due to symptoms such as dyspnoea impacting appetite and food intake and also because hypoxia and increased systemic inflammation alter protein metabolism and nutrient requirements. Malnutrition is likely both a cause and consequence of worsening CLD.
Obesity is a recognised risk factor for the development of certain CLD. It is also important to note the potential obesity has to mask malnutrition and/or sarcopenia, both of which influence disease progression. An obesity paradox exists because having a higher BMI is associated with lower mortality rates in those with severe CLD. The mechanism is not fully understood but it could possibly be due to having increased energy reserves at times when illness tends to cause nutrition intake to significantly decline.
What are some of the challenges for managing malnutrition in respiratory illnesses?
One of the biggest challenges is that dietitians are often not allocated to respiratory service MDTs which limits the proactive development of respiratory nutrition services. This is despite increasing evidence to support nutrition interventions in CLD, such as the recommendations in the 2012 Cochrane Review, on Nutrition Support in Chronic Obstructive Pulmonary Disease (COPD), supporting the treatment of malnutrition.
A major challenge to identifying malnutrition is that although nutrition screening of patients routinely occurs on admission to hospital, it is less consistent in respiratory outpatients and other community settings. Rather than seeing malnutrition as an inevitable consequence of CLD, a proactive approach to identifying patients at risk of malnutrition with appropriate nutrition screening tools in these settings is needed.
The strongest evidence for the benefits of treating malnutrition in CLD is for interventions made earlier in the course of the disease.
What further studies/research would be needed to improve the understanding of this area?
Nutrition screening
Nutrition is not included as a quality outcome indicator for COPD or any other respiratory condition, and although NICE published recommendations for nutrition screening of high-risk community and outpatient groups in 2006, there is no requirement for screening rates to be reported like there currently is for hospital inpatients.
Further studies are needed to establish current outpatient and community nutrition screening rates for those with CLD and the impact this has on outcomes.
Body composition and muscle loss
International recommendations suggest assessment of muscle loss should be incorporated into nutrition screening for those with CLD. Research is needed into whether current nutrition screening methods used in the UK could be improved with additional sarcopenic obesity screening.
Benefits of having a Dietitian
Dietitians have the specialist knowledge and skills to provide individualised patient-led nutrition advice. Patients with CLD have complex nutrition issues due to ongoing disease symptoms, the presence of malnutrition, obesity, comorbidities, sarcopenia or a combination of these.
Evidence to show the benefits of having a dietitian within the respiratory team is limited, likely impacting on current funding for respiratory dietitians. A comparison of teams with and without a dietitian working as part of the MDT is needed to investigate the impact this may have on nutrition knowledge, attitudes to nutrition issues, nutrition interventions and patient health outcomes.
Pulmonary rehabilitation (PR)
There is currently no UK-specific guidance for nutrition screening, nutrition education or nutrition-focused outcomes in PR. There is some evidence to show that assessment of nutritional status followed by intervention during PR appears to improve outcomes, but it is difficult to determine if the benefits are attributable to the nutritional interventions or the rehabilitation programme. International guidance recommends that each element of PR is carried out by an expert, so further studies are needed to explore the involvement of dietitians to undertake nutrition screening and education in PR.
What advice would you give to colleagues interested in learning more about nutrition in respiratory health?
I would advise respiratory team health professionals to read the European Respiratory Society (ERS) statement on nutritional assessment and therapy in COPD which was published in 2014. It was developed by a multidisciplinary task force with the aim of raising awareness and assisting clinicians to improve nutritional care. It was followed up in 2023 with a summary of evidence published since, which concludes that nutritional assessment and treatment have significant potential to improve clinical outcomes in COPD.
I encourage respiratory teams to explore their own nutrition practices and the provision of dietetic services and consider how better collaboration and MDT working could improve overall respiratory care and health outcomes for their patients.
I would also hope that the British Thoracic Society will consider including nutrition in any appropriate future guidance.