Nutritional support, mainly in the form of oral nutritional supplements, has a significant upside in patients with chronic obstructive pulmonary disease (COPD), according to a new systematic review and meta-analysis.
Based on the review, "clinicians can have confidence" that nutritional support in COPD patients leads to "significant improvements in energy and protein intakes resulting in substantial increases in body weight by a level (~2 kg) that is associated with functional improvements," Dr Marinos Elia, from the Institute of Human Nutrition, University of Southampton, United Kingdom, told Reuters Health in an email.
"Currently there is confusion around the efficacy of nutritional support in the treatment of malnutrition in COPD and as a result questions have arisen around the value of screening for malnutrition in this patient group," Dr Elia and co-authors Peter F. Collins (first author) and Rebecca J. Stratton wrote in an April 18th paper online in the American Journal of Clinical Nutrition.
"Previous reviews and meta-analyses concluded that nutritional support was ineffective in the treatment of malnutrition, however, numerous trials have suggested this not to be the case," Dr Elia added.
Weight gain associated with clinical benefits
To investigate further, the study team searched PubMed, Web of Science and OVID literature databases for randomised controlled trials of nutritional support in COPD. They identified and included in their meta-analysis a total of 13 RCTs involving 439 patients with COPD who were randomly assigned to a treatment group (n=224) or a control group (n=215).
Treatment included nutritional support in the form of dietary advice and a milk powder supplement (1 trial), enteral tube feeding (1 trial) and oral nutritional supplements (ONS, 11 trials). The ONS trials used mostly liquid supplements, some of which were specially formulated for use in COPD. Most of the trials were principally of malnourished ("depleted") individuals.
The investigators note that previous meta-analyses failed to examine changes in dietary intake. Theirs did examine nutritional intake, and it showed that nutritional support led to a significantly greater increase in both protein and energy intakes.
They also found greater average improvements in favour of nutritional support for body weight (1.94 kg; p<0.001, 11 studies with 308 subjects) and grip strength (5.3%; p<0.050, 4four studies with 156 subjects). The authors say a weight gain of approximately two kg in COPD is likely to be associated with functional and clinical benefits.
Limitations in trials
Dr Elia told Reuters Health, "Recommendations made by organisations such as NICE (National Institute of Health and Clinical Excellence) and ESPEN that oral nutritional supplements (ONS) be prescribed to COPD patients with a body mass index (BMI) <20 kg/m2 appear with a lower grade of evidence than that suggested by our analyses."
"In patients with a BMI <18.5 kg/m2 it is likely that additional input will be required from a dietician to maximise oral nutritional intake from food at the same time as ONS. Ideally any COPD patient identified as at risk of malnutrition should be referred to a dietician, however, this is not always possible in the community setting," Dr Elia said.
Limitations of the current meta-analysis include a limited number of included studies (13 totals, with 10 judged to be of poor quality). The fact that most trials used ONS is another limitation; the data are "weak or lacking" for other forms of nutritional support (e.g., snacks) or dietary modification/fortification.
The authors also point out that 10 of the 13 trials were done before 2000, when the first Cochrane Review on the topic - which included most of the current evidence - concluded that nutritional support has no effect on COPD.
Differences in methodology
"This may have dampened interest in the field; however, it is hoped that the positive findings of this review will highlight the need to undertake further work, including an examination of the interactions that might exist between nutritional supplementation and factors such as malnutrition, inflammatory status, and graded physical activity in both stable disease and infective exacerbations of COPD," the authors conclude.
One of the authors on the paper is an employee of Nutricia Ltd. None of the other authors declared a conflict of interest.
Dr Ivone Martins Ferreira from Toronto Western Hospital and McMaster University, Ontario, Canada, who was not involved in this review but did work on a 2005 Cochrane Database Review of nutritional supplementation in stable COPD, told Reuters Health: "It is reassuring to see that a different group of researchers performed a very similar search and meta-analysis and included exactly the same papers that we included in our previous meta-analysis, suggesting that we did not exclude relevant papers. Interestingly, the results are different than ours. The authors did state that this was due to a difference in methodology."
Results will lead to further trials
"We did not find evidence of statistically significant improvement in weight or anthropometric measures. Collins and colleagues apparently did find significant improvement. It would be interesting to know if the difference between results was due, in part, to the fact they did not include data in the meta-analysis for mid-arm muscle circumference from at least two included papers," Dr Ferreira commented.
"Our hope is that these results will stimulate discussion and hopefully lead to further trials. Plurality of opinions has always contributed to the advancement of science, as it always promotes revisions and an improvement in outcomes; and improvement in outcomes in COPD is our ultimate goal."
In particular, Dr Ferreira added, "studies to evaluate combinations of enhanced nutrition, anti-inflammatory supplements, exercise, etc., are welcomed and needed."
(Megan Brooks, Reuters Health, May 2012)
Treatment and monitoring of COPD