To the Editor:
We read with great interest the article by Guo et al. reporting on the association of air pollution (AP) with metabolic dysfunction-associated fatty liver disease (MAFLD).
[1]
We appreciate the authors conducted a great cohort study and provided a novel perspective. However, we would like to highlight some key points.Firstly, the authors reported the odds ratios (ORs) of MAFLD associated with AP, stratified by demographic and lifestyle factors in Table 2. However, we are worried that some important residual confounders might exist, especially the annual household income and education level because of the association with the prevalence of diabetes, which was one of the criteria of MAFLD.
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Moreover, income and education levels could also affect lifestyle and quality of life. Therefore, we suggest the authors may add another co-medication status (e.g. income and education level) in the stratified analyses to avoid residual confounders.Secondly, the authors indicated sex may influence the association between AP and MAFLD, and males had significantly higher MAFLD prevalence than females in overweight or obese adults.
[5]
In other words, sex was an independent risk factor for MAFLD. In addition, according to Table 2, PM2.5 and PM10 seemed not to have a significantly additive effect with central obesity, which seems to be a contradiction. Hence, we suggest that the authors propose more mechanisms to explain their results.Lastly, the authors indicated that the OR of MAFLD associated with AP were greater in the non-diabetic group, but not significantly different. We are concerned that there could be type I error, because AP could exacerbate the parameters of diabetes.
[6]
Thus, we suggest that the authors should match or adjust co-medication status in the stratified analyses.The study result is interesting and provocative. Yet, we recommend that residual confounders should be considered and more potential mechanisms proposed to further develop on the results of this study.
Financial support
This article received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Authors' contributions
Conceptualization, Y.-S.C. and J.C.-C.W.; Supervision, Y.-M.H. and J.C.-C.W.; Writing—original draft, Y.-S.C.; Writing—review & editing, Y.-M.H. and J.C.-C.W. All authors have read and approved the final manuscript.
Conflict of interest
The authors have no conflicts of interest that pertain to this work to declare.
Please refer to the accompanying ICMJE disclosure forms for further details.
Supplementary data
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References
- Exposure to air pollution is associated with an increased risk of metabolic dysfunction-associated fatty liver disease.J Hepatol. 2022; 76: 518-525
- A new definition for metabolic dysfunction-associated fatty liver disease: an international expert consensus statement.J Hepatol. 2020; 73: 202-209
- Diabetes prevalence and its relationship with education, wealth, and BMI in 29 low- and middle-income countries.Diabetes Care. 2020; 43: 767-775
- Worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4.4 million participants.Lancet. 2016; 387: 1513-1530
- Estimating global prevalence of metabolic dysfunction-associated fatty liver disease in overweight or obese adults.Clin Gastroenterol Hepatol. 2021;
- Impacts of ambient air pollution on glucose metabolism in Korean adults: a Korea National Health and Nutrition Examination Survey study.Environ Health. 2020; 19: 70
Article info
Publication history
Published online: January 21, 2022
Accepted:
December 24,
2021
Received:
December 21,
2021
Footnotes
Author names in bold designate shared co-first authorship
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Copyright
© 2022 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
