Systematic Review On The Correlation Between Lung Function Or Eosinophil Levels And Quality Of Life In Asthma


      Asthma is an inflammation of the respiratory functions characterized by symptoms such as dyspnea, wheezing, sputum production and cough that can significantly affect quality of life. The objective of this review was to explore the evidence on the possible correlation between lung function (FEV1 or FVC or PEF) or eosinophil levels and quality of life in asthmatic patients.


      A literature search was made using keywords such as “asthma”, “eosinophil”, “quality of life”, and “respiratory function”. The search was conducted in the electronic databases MEDLINE, EMBASE and PubMed from January 2000 to February 10th, 2015. To be eligible, studies had to focus on asthmatic patients, include pulmonary or eosinophil measurements, and quality of life data.


      The review allowed retrieving 5,776 studies and 42 fulfilled the eligibility criteria. Twenty-five articles presented a correlation coefficient between lung function and quality of life. All, except one, conclude to a positive correlation between lung function and quality of life with R-values ranging from 0.008 to 0.790. Of the 25 studies, 36% obtained an R-value of 0.4 and over, indicating a weak to moderate correlation. Sixteen of these results were statistically significant. One article evaluated the correlation between sputum eosinophil levels and AQLQ and concluded to a non-statistically significant correlation with an R-value of -0.15. Fourteen articles did not evaluate the direct correlation between the parameters of interest but presented raw data of these parameters. Of these, 12 studies presented data that indicate a correlation between FEV1 and quality of life with an increase in quality of life score, when FEV1 increases.


      The correlation coefficients found in the systematic review indicate that when lung function improves, and possibly when sputum eosinophil decreases, the quality of life improves. Furthermore, non-correlation studies that look at the same parameters support this hypothesis.