A positive correlation was identified between high metabolism scores for visceral fat (METS-VF) and increased asthma risk, according to new study findings published in Frontiers in Endocrinology.
“The prevalence of asthma and METS-VF is positively correlated, but the relationship isn’t linear,” wrote the researchers of the study. To their knowledge, this study is the first of its kind to examine the association between METS-VF and asthma prevalence.
Prior studies have identified a bidirectional relationship between obesity and asthma, in which patients classified as obese were more likely to report continuous asthma symptoms, miss more days at work, and use more medications. Additionally, these patients were found less likely to have asthma remission and more likely to have severe persistent asthma.
However, accurately assessing the real situation of obesity can be difficult, with body mass index (BMI) only able to offer a limited and rough indicator of obesity. Furthermore, BMI lacks the ability to differentiate between fat mass and lean mass, as well as local fat distribution patterns, the authors noted.
In contrast, the METS-VF is a measure of exposure to adipose tissue that combines insulin resistance index (calculated with triglyceride and fasting blood glucode level), waist to height ratio, age, and sex.
Using data from the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2018, the researchers aimed to define a relationship between METS-VF and asthma.
The survey included 91,352 individuals. Participants met eligibility criteria if they had complete information for METS-VF, education, marital status, hypertension, diabetes, smoking, activity, asthma, coronary heart disease, cancer, and serum uric acid. After exclusion, 36,876 participants were included in the analysis, and 4919 of these individuals had self-reported asthma.
The researchers identified a positive correlation between METS-VF and asthma prevalence (odds ratio [OR], 1.27; 95% CI, 1.22-1.32; P = .01), which grew stronger when METS-VF was elevated at an inflection point of 5.24. Additionally, according to smooth curve fitting analysis, the relationship between METS-VF and asthma was not linear.
Further double-segmented analysis suggested a negative correlation, but no significant difference between METS-VF less than 5.24 and asthma prevalence (OR, 0.60; 95% CI, 0.33-0.91). After METS-VF exceeded 5.24, all positive correlations between METS-VF and asthma prevalence were stable.
Lastly, after subgroup analysis, the researchers identified METS-VF associated with asthma prevalence among participants who were aged 40 to 59 years (OR, 1.35; 95% CI, 1.26-1.44), were male (OR, 1.79; 95% CI 1.20-2.68), reported Mexican American ethnicity (OR, 1.41; 95% CI, 1.28-1.54), had hypertension (OR, 1.23; 95% CI, 1.23-1.38) and diabetes (OR, 1.36; 95% CI, 1.23-1.50), and lacked a history of asthma (OR, 1.29; 95% CI, 1.23-1.36).
The researchers acknowledged some limitations to the study, including being cross-sectional, so a causal relationship could not be established; basing an asthma diagnosis on self-reported information; and the possibility of covariates that may have influenced factors of METS-VF and asthma.
Despite these limitations, the researchers believe a strength of this study is in its ability to identify a positive association between elevated METS-VF and asthma prevalence.
“An increase in the METS-VF index is associated with an increase in the incidence of asthma,” wrote the researchers. “The hypothesis is that treatment and management of obesity at a young age may delay, ameliorate, or reduce the onset of asthma, but a causal relationship cannot be clearly established, but this is of clinical concern nonetheless.”
Liu Q, Han X, Chen Y, Gao Y, Yang W, Huang L. Asthma prevalence is increased in patients with high metabolism scores for visceral fat: study reports from the US. Front Endocrinol (Lausanne). Published online May 16, 2023. doi:10.3389/fendo.2023.1162158