Insulin resistance, metabolic syndrome, and lung function in US adolescents with and without asthma

Abstract

Background: Obesity increases both the risk of asthma and asthma severity and is a well-known risk factor for insulin resistance and the metabolic syndrome (MS) in children and adolescents.

Objective: We aimed to examine the association among obesity, insulin sensitivity, MS, and lung function in US adolescents with and without asthma.

Methods: We performed a cross-sectional study of 1429 adolescents aged 12 to 17 years in the 2007-2010 National Health and Nutrition Examination Survey. Adjusted regression was used to assess the relationships among obesity, insulin sensitivity/resistance, MS, and lung function in children with and without asthma.

Results: Insulin resistance was negatively associated with FEV1 and forced vital capacity (FVC) in adolescents with and without asthma, whereas MS was associated with lower FEV1/FVC ratios, with a more pronounced decrease found among asthmatic patients; these associations were driven by overweight/obese adolescents. Higher body mass index was associated with a decrease in FEV1/FVC ratios among adolescents with insulin resistance. Compared with healthy participants, adolescents with MS had an approximately 2% decrease in FEV1/FVC ratios, adolescents with asthma had an approximately 6% decrease, and those with MS and asthma had approximately 10% decreased FEV1/FVC ratios (P < .05).

Conclusion: Insulin resistance and MS are associated with worsened lung function in overweight/obese adolescents. Asthma and MS synergistically decrease lung function, as do obesity and insulin resistance. These factors might contribute to the pathogenesis of asthma severity in obese patients and warrant further investigation.

Keywords: Asthma; National Health and Nutrition Examination Survey; adiposity; insulin resistance; lung function; metabolic syndrome; obesity.

Figure 1. BMI z-score and lung function by insulin resistance status

Predicted values for FEV₁ and FEV₁/FVC by insulin resistance status (HOMA-IR<3.0 vs >3.0). All models adjusted for age, gender, race/ethnicity, asthma status, health insurance coverage, family history of asthma, ETS exposure, fasting hours, and C-reactive protein. Interaction P-value for FEV₁ = 0.0006, and for FEV₁/FVC = 0.02.

Figure 1. BMI z-score and lung function by insulin resistance status

Predicted values for FEV₁ and FEV₁/FVC by insulin resistance status (HOMA-IR<3.0 vs >3.0). All models adjusted for age, gender, race/ethnicity, asthma status, health insurance coverage, family history of asthma, ETS exposure, fasting hours, and C-reactive protein. Interaction P-value for FEV₁ = 0.0006, and for FEV₁/FVC = 0.02.

Figure 2. Predicted FEV₁/FVC by asthma and metabolic syndrome status

All models adjusted for age, gender, race/ethnicity, health insurance coverage, family history of asthma, ETS exposure, fasting hours, C-reactive protein, and z-score for each respective adiposity indicator (BMI, PBF, WC, or WHtR). MS=metabolic syndrome. No asthma & no MS n=496; MS only n=58; asthma only n=23; and MS & asthma n=7. *P<0.05 compared to control group (no asthma & no MS).