BMI can influence adult males’ and females’ airway hyperresponsiveness differently

Abstract

BackgroundEpidemiological data indicate that obesity is a risk factor for asthma, but scientific literature is still debating the association between changes in body mass index (BMI) and airway hyperresponsiveness (AHR).MethodsThis study aimed at evaluating the influence of BMI on AHR, in outpatients with symptoms suggestive of asthma.4,217 consecutive adult subjects (2,439 M; mean age: 38.2±14.9 yrs; median FEV1 % predicted: 100 [IQR:91.88-107.97] and FEV1/FVC % predicted: 85.77% [IQR:81.1-90.05]), performed a methacholine challenge test for suspected asthma. Subjects with PD20 < 200 or 200 < PD20 < 800 or PD20 > 800 were considered affected by severe, moderate or mild AHR, respectively.ResultsA total of 2,520 subjects (60% of all cases) had a PD20 < 3,200 μg, with a median PD20 of 366 μg [IQR:168–1010.5]; 759, 997 and 764 patients were affected by mild, moderate and severe AHR, respectively. BMI was not associated with increasing AHR in males. On the contrary, obese females were at risk for AHR only when those with moderate AHR were considered (OR: 1.772 [1.250-2.512], p = 0.001). A significant reduction of FEV1/FVC for unit of BMI increase was found in moderate AHR, both in males (β = −0.255; p =0.023) and in females (β = −0.451; p =0.017).ConclusionsOur findings indicate that obesity influences AHR only in females with a moderate AHR level. This influence may be mediated by obesity-associated changes in baseline lung function.

Obesity can influence children’s and adolescents’ airway hyperresponsiveness differently

“…This means that a BMI increase determines functional alterations consistent with an obstructive pattern in female adolescents. This is in accordance with a previous study of ours, carried out on adults, where we found a significant reduction of FEV 1 /FVC ratio only in females with moderate AHR [ 20 ]. Also other researchers found a FEV 1 /FVC reduction both in obese children [ 6 ] and adults [ 36 ], though this was not confirmed by other authors [ 32 , 37 ].…”

“…The risk evaluation in the two sexes showed that it was 38% greater in females when compared to males. This means that obesity influences only female adolescents and not male adolescents or children, which is perfectly in line with what was assessed in another study of ours [ 20 ] and in previous researches [ 23 , 25 , 26 ] where a higher AHR risk was observed only in adult females. Female adolescents become adults more precociously than males.…”

“…Besides, studies often associate children with adolescents, without taking into account that puberty can influence asthma differently [ 19 ]. Also smoking can have a negative impact on bronchial hyperreactivity [ 20 ].…”

The effects of obesity on asthma: immunometabolic links

“…35 Likewise, obesity was not associated with AHR in men, while such an effect was observed in women with moderate AHR. 36 In another study, sex had no effects on obesity -asthma association in children, but trunk predominant (central) adiposity was significantly associated with asthma only among women. 37 Overall, epidemiological studies suggest that the effects of obesity on asthma are greater in women, which seems to be related to the activity of estrogens.…”

The Asthma Phenotype in the Obese: Distinct or Otherwise?

“…Obesity itself is not associated with airflow obstruction [29]. However, since obese individuals do breathe at lower lung volumes, the resulting airway narrowing may contribute to heightened airway hyperreactivity [30–32], with one study noting the association only in females [33]. This latter observation may be due to a subgroup effect among the late-onset non-atopic obese asthma phenotype described above, as Dixon et al [34] demonstrated that obese asthmatics who had a low serum IgE (presumably late-onset of asthma) had improved airway hyperreactivity 12 months after bariatric surgery, but those with elevated serum IgE (presumably early onset of asthma) did not.…”