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In non-diabetic subjects with the metabolic syndrome and a lung function that is within the normal range, visceral fat is negatively correlated with FEV1 and FVC.

BackgroundObesity is a risk factor for the development of asthma. In patients with obesity the diagnosis of asthma is often based on symptoms, but without objective measurements. Nevertheless, obesity-associated asthma is recognized as a distinct asthma phenotype. Therefore, this study explores lung function and symptoms in asthma patients with and without obesity.MethodsThe Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort study with 6671 participants (aged 45–65 years) of whom 472 had asthma. Of this latter group, linear regression analysis was used to examine differences in lung function and symptoms between asthma patients with (n = 248) and without obesity (n = 224), and between asthma patients with and without increased FeNO. Analyses were adjusted for confounders.ResultsAsthma patients with obesity had lower predicted FEV1 and FVC values than patients without obesity [adjusted mean difference (MD) -3.3% predicted, 95% CI -6.5, −0.2; adjusted MD −5.0% predicted, 95% CI -7.8, −2.1]. The prevalence of symptoms was higher in patients with obesity. Asthma patients with obesity and with increased FeNO had lower FEV1 and FEV1/FVC values compared with those with low FeNO (adjusted MD −6.9% predicted, 95% CI -11.7, −2.0; −2.4%, 95% CI -4.6, −0.2).ConclusionAsthma patients with obesity had lower FEV1 and FVC values than patients without obesity. This suggests that patients with obesity have restrictive lung function changes, rather than obstructive changes. Asthma patients with obesity and increased FeNO showed more obstructive changes. FeNO might help to identify patients with eosinophilic inflammation-driven asthma, whereas patients with low FeNO might have an obesity-associated asthma phenotype in which symptoms are partly caused by the obesity.Electronic supplementary materialThe online version of this article (10.1186/s12931-017-0684-9) contains supplementary material, which is available to authorized users.

Vitamin D is hypothesized to have a beneficial effect on lung function and respiratory infections. The aim of this study was to assess the relationship of serum 25-hydroxyvitamin D (25(OH)D) concentrations with lung function, airway inflammation and common colds. We performed a cross-sectional analysis in the Netherlands Epidemiology of Obesity (NEO) study, a population-based cohort study. We included participants with measurements of serum 25(OH)D, Forced Expiratory Volume in 1 s (FEV1), Forced Vital Capacity (FVC), Fractional Exhaled Nitric Oxide (FeNO), and data on self-reported common colds (n = 6138). In crude associations, serum 25(OH)D was positively associated with FEV1 and FVC, and negatively with FeNO and the occurrence of a common cold. After adjustment for confounders, however, these associations disappeared. Stratified analyses showed that Body Mass Index (BMI) was an effect modifier in the relationship between serum 25(OH)D and FEV1, FVC and FeNO. In obese participants (BMI ≥ 30 kg/m2), 10 nmol/L higher 25(OH)D was associated with 0.46% predicted higher FEV1 (95% Confidence Interval: 0.17 to 0.75), 0.46% predicted higher FVC (0.18 to 0.74), and 0.24 ppb lower FeNO (−0.43 to −0.04). Thus, in the total study population, 25(OH)D concentrations were not associated with lung function, airway inflammation and common colds. In obese participants, however, higher 25(OH)D concentrations were associated with a better lung function and lower airway inflammation.