Healthy behaviours and COPD

Abstract

@ERSpublicationsHealthy behaviours (diet and activity) could have beneficial effects on the risk of COPD occurence or progression http://ow.ly/AhjNhIn this issue of the European Respiratory Review, YOUNG and HOPKINS [1] elegantly discuss how beans (an important part of the Hispanic diet) could reduce systemic inflammation and, thereby, the risk of chronic obstructive pulmonary disease (COPD) and lung cancer, explaining the risk imbalance between Hispanics, African-Americans and non-Hispanic whites. As appropriately acknowledged by the authors, what they propose is a hypothesis, warranting confirmation in specific observational and interventional studies. The purpose of this editorial is to discuss some important issues evoked in their reasoning, focusing on COPD only. Altogether, the main question is: is causal inference between bean intake and reduction in the risk of COPD occurrence possible from available data and, if not, what would be needed to progress, considering possible confounders?Assessing the causality of the link: back to basicsIn 1965, Sir Bradford Hill, an epidemiologist, proposed to consider the following criteria when assessing the causality of a relationship between two events/conditions [2]: 1) the strength of the association, as assessed by statistics (rate ratios, risk ratios and odds ratios); 2) consistency and repeatability of the association; 3) specificity of the relationship (one cause leads to one effect); 4) temporal relationship (the cause precedes the consequence); 5) presence of a dose-response relationship, i.e. greater exposure is associated with greater incidence of the effect; 6) biological plausibility; 7) coherence between epidemiological and biological/laboratory evidence; 8) experimental evidence; and 9) analogy with the effect of other, similar factors. Two other factors need to be considered: 1) the possible involvement of bias by confounding factors in the observed association(s) [3]; and 2) the specific issue of confirmation of observations by interventional approaches [4]. The need to consider the criteria of HILL [2] as a guide rather than as a definitive tool has been underlined previously, especially in the area of nutritional epidemiology [5]. Bearing these considerations in mind, what is the evidence linking diet and COPD occurrence, and how can other dietary components or non-dietary factors confound the possible link between bean consumption and COPD? Biological plausibilityIn COPD, the main dietary components that have attracted interest are fibre (mostly contained in fruits and vegetables, including beans), polyunsaturated fatty acids (PUFAs) and antioxidant micronutrients (vitamins A, C, D and E, and carotenes and flavonoids), as recently reviewed elsewhere [6,7]. These components are actually inter-related: for instance, fermentation of water-soluble fibres in the large intestine promotes the

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“…Based on other previous studies, consumption of certain fruits, vegetables, whole grains, and fish may prevent COPD, while consumption of processed foods may increase the prevalence of COPD [ 12 , 13 ]. A healthy diet has protective effects on the biological processes involved in lung function, disease development, and outcomes [ 9 ].…”