Are dietary factors associated with lung function in Canadian adults?

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Résumé (anglais)

Background: Assessment of lung function by spirometry is helpful for evaluating lung health. It provides precise measurements of air volumes and flows useful for diagnosis and monitoring of respiratory diseases. Respiratory diseases (including asthma and COPD) are some of the major causes of school and work absenteeism, hospital admission, disability, and death. Diet is a modifiable risk factor that has been associated with various respiratory outcomes but has been studied minimally in relation to lung function. Purpose: The purpose of this study was to explore the impact of dietary factors and nutrient biomarkers on lung function among Canadian adults (18 years and older). Methods: The Canadian Health Measures Survey (CHMS) is a national and ongoing health survey of Canadians led by Statistics Canada. CHMS uses a repeated cross-sectional multi-stage survey design. Data collection included a combination of a computer-assisted personal interview and physical assessment. The first Cycle (2007-2009) included N=3726, the second Cycle (2009-2011) included N= 3873, and the third Cycle (2012-2013) included N= 3397 adult Canadians. The physical measures were conducted at Mobile Examination Centers (MEC) specifically designed for the study. Spirometry measurement was completed by the eligible participants following spirometric guidelines of the American Thoracic Society (ATS). The household and clinic questionnaires were used to assess individual dietary factors, Canada Food Guide, and Modified Mediterranean Diet Score separately for each of the Cycles. Biomarker assessment was done by using blood samples. Association analyses were completed using multiple linear regression adjusting for age, sex, and height as well as other confounders using sampling weights. Bootstrapping variables supplied by Statistics Canada were used to calculate variances. Results: The overall mean percent predicted values for FVC and FEV1 were 98% and 95%, respectively. The associations between dietary consumption and lung function were relatively inconsistent. However, in both Cycles 1 and 2, consumption of dietary fat was associated with higher FVC (p<0.05). In all Cycles, most of the participants did not meet the daily requirement of Canada Food Guide and the "not meeting" the requirements were inconsistently associated with the lower lung function. The modified Mediterranean Diet Score was significantly associated with lower lung function in Cycle 3. Among the biomarkers, chloride was associated with higher FVC and FEV1 for all three Cycles (p<0.05). C-reactive protein was associated with lower FVC, FEV1, and FEF25-75% (Cycle 1, 3. p<0.05). Vitamin D was associated with higher FEV1 (Cycle 1, 3. p<0.05). Finally, Vitamin B12 was associated with lower FEV1 (Cycle 1, 3. p<0.05). Conclusion: Lung function characteristics shows good lung health of the general adult population based on the mean percent predicted values. Our study provides evidence that there is an association between dietary factors and lung function though there were some inconsistencies with different Cycles (Cycles 1, 2, 3) mostly within the report of dietary intake.