In a recent study published in BMC Public Health, researchers investigated the association between diet quality measured by the Healthy Eating Index-2010 (HEI-2010) score and the odds of Chronic obstructive pulmonary disease (COPD) in the Iranian population.

Study: The association between diet quality and chronic obstructive pulmonary disease: a case-control study. Image Credit: ME Image/Shutterstock.com

Background 

COPD is a pressing global health concern, ranking as the third leading cause of death as per World Health Organization (WHO). Primarily linked to smoking and factors like aging, the prevalence of COPD is on the rise, with a global average rate of 13.1%, but variations exist across countries.

Complications like pneumonia, lung cancer, and cardiovascular diseases often accompany COPD, increasing economic burdens, as seen in the United States of America’s (USA’s) jump from $32.1 billion in 2010 to $49 billion in 2020. Research suggests that, in addition to smoking, diets rich in fiber, fruits, and fish significantly impact COPD incidence.

While the HEI assesses diet quality and is related to conditions like obesity and diabetes, its connection to COPD is uncharted.

Given varying regional dietary habits, nutritional shifts in developing countries, and diverse COPD-contributing factors globally, further research is needed for a holistic understanding of the diet-COPD relationship in varied contexts.

About the study 

In the present case-control study at Al-Zahra University Hospital in Isfahan, Iran, from 2015 to 2016, researchers examined the relationship between diet and COPD. Using calculations that accounted for various factors, they determined a sample of 84 cases with COPD and 252 controls without the disease.

Selection of the COPD cases was done randomly from the hospital database, ensuring minimal bias. Patients over 30 with a pulmonologist’s diagnosis of COPD based on specific spirometry test results were included. Controls, matched by age and sex to the cases, were sourced from the same hospital’s outpatient clinics.

To ensure data accuracy, various exclusions were applied to potential participants based on various health conditions.

Using a 168-item food frequency questionnaire (FFQ), dietary intakes over the past year were assessed and then translated into daily intake amounts to calculate nutrient intakes using specific software. The HEI-2010 was employed as a dietary assessment metric, which utilizes various food groups to evaluate diet quality.

Spirometry testing by a trained technician evaluated pulmonary function. Additional data on socio-demographic details, physical measurements, and lifestyle behaviors were also gathered.

Smoking behaviors were documented through a specific questionnaire. The data were statistically analyzed with significant results marked at p < 0.05.

Study results 

Several observations were made in the present study, evaluating the characteristics and dietary habits of cases and controls. The study revealed that cases frequently had a history of pulmonary conditions and were less inclined towards physical activity, education, and employment.

Additionally, they were less often married and less commonly owned cars or homes. When assessing smoking behaviors, the cases were more frequently active or passive smokers, water pipe users, or even non-smokers. On the other hand, controls showed a higher likelihood of being ex-smokers.

When examining the distribution of participants based on the HEI-2010 score quartiles, a nutritional assessment tool, it was observed that control participants in the highest quartiles tended to be older, employed, physically active, and more likely to own a car or home compared to those in the lowest quartile.

For the cases, those in the top HEI-2010 quartile were less often married but were better educated and owned cars or homes more often than those in the lowest quartile.

Regarding smoking, cases in the top HEI-2010 quartile were more frequent smokers but less likely to be non-smokers, whereas controls in this quartile were less likely to smoke or use water pipes and more likely to be non-smokers, also known as passive smokers.

The study illustrated that cases commonly experienced severe disease symptoms, including phlegm and cough, as anticipated. Controls, in contrast, often had a better lung function, evidenced by higher Forced Expiratory Volume in 1 second (FEV1) predicted value, Forced Vital Capacity (FVC), and FEV1/FVC ratio.

Differences in dietary intake between cases and controls were noted across HEI-2010 score quartiles, with cases generally consuming more energy, carbohydrates, and vitamin A. Specific food group consumptions showed cases ate more dairy and empty calories but less seafood, plant proteins and whole grains.

A deeper dive into these dietary differences revealed that cases in the top HEI-2010 quartile had increased intakes of various nutrients, including carbohydrates, energy, protein, fiber, fats, riboflavin, calcium, and several vitamins, as well as higher consumption of certain food groups. Similarly, controls in this quartile had increased intake of several nutrients and food groups.

The present study also focused on COPD cases, highlighting a noteworthy observation: severe COPD patients had a higher HEI-2010 score and consumed more whole grains than those with milder COPD.

Lastly, logistic regression findings demonstrated a significant association between adherence to HEI-2010 recommendations and a decreased likelihood of having COPD. Individuals with higher compliance to these dietary guidelines had substantially reduced odds of COPD.

Even after adjusting for potential confounding factors like smoking, physical activity, and BMI, this strong association persisted.