Increased BMI has been associated with poor asthma control in multiple studies, yet the association is complex and conflicting results are shown in different studies. The effect of age on poor asthma control in adults have shown that older age is usually associated with more severe asthma and poorer control because of the presence of other comorbidities. This was not the case in our study where younger age ≤ 45 had poorer disease control compared to older age. This may have been due to a selection bias since the mean age of our population is 38.5. This is most likely due to the fact that the population is selected from an allergy clinic where the population is in general younger. Indeed, in our study 80% of the patients showed aeroallergen sensitization, which is as well a selection bias. Allergic sensitization was not significantly associated with higher BMI or poorer asthma control: in both controlled and uncontrolled asthmatics, the percentage of allergic patients was much higher than the non-allergic. As far as gender, studies have shown that females are more likely to have poor disease control compared to males [
15]. In our study, we had a higher percentage of females (65.57%) than males. Even though their association with poor asthma control was almost significant with females being more likely to have poorer control than males, the association with higher BMI was not statistically significant; indeed, we had almost the same number of female patients being of normal weight or overweight/obese. In the western world, it seems that females are more likely to be overweight [
16]. Generally, this is not true in Lebanon where females are more concerned about their weight and body image [
17]. Gender did not significantly affect the association between poor asthma control and BMI. The association with higher BMI was significant, where patients who have a graduate or postgraduate degree are more likely to have a higher BMI compared to patients who were undergraduates, but this association is still being studied to further strengthen this notion [
18]. The association between graduate studies and poor asthma control was barely significant in the bivariate analysis of this study, even though almost 68% of patients who had graduate or postgraduate degrees, had poor asthma control as defined by the ACT. The presence of childhood asthma is not, in general, a risk factor for poor disease control in adulthood. There are no conclusive studies showing that the history of childhood asthma is associated with poor disease control in adults. Conversely, few studies have shown that a patient with a history of childhood asthma may be more aware of asthma management and therefore better controlled. Recent pediatric asthma guidelines include inhaled rather than oral corticosteroids for childhood asthma, therefore limiting the effect of treatment-induced weight gain in asthmatic. Our study showed no significant association between the history of childhood asthma with neither higher BMI nor poor asthma control. In our study, only 22% of our patients were cigarette or waterpipe smokers. This is a main selection bias and does not reflect the prevalence of cigarette or waterpipe smokers among the Lebanese population. One possible explanation may be that since we have a higher percentage of uncontrolled asthmatics, those prefers to avoid smoking since it will worsen their respiratory symptoms and exacerbate their asthma, although studies showed that allergic or asthmatic patients do not avoid smoking [
19]. In our study, smoking was not associated with higher BMI, neither with poor asthma control. Again this may be due to a low percentage of smokers among our population. A study we previously conducted to explore the effect of parental smoking on asthma exacerbation of their children showed that only 28% of parents were smokers [
20] .
Adherence to asthma therapy is the subject of numerous publications in developed countries [
21]. In general, adherence to therapy may vary across cultures but it is a fact that non-compliance to therapy is associated with poor asthma control [
22]. Therefore, medical authorities in developed countries devote a lot of resources on asthma education in an attempt to overcome the factors associated with non-adherence. Among those factors are: patients’ beliefs and goals, lack of time given by physicians to explain and supervise inhaler techniques, economic problems and much more. Social desirability bias should be taken into account, because the treating physician or his clinic assistant assessed adherence to therapy. In our study, compliance was found to be present in approximately 64% of cases; there was no association with higher BMI, but it seemed that non-compliant patients have poor asthma control.
This study has several limitations. First, it is cross-sectional, thereby introducing a potential selection bias. Another limitation of this study design is that it can investigate an association between overweight/obesity and poor asthma control but it cannot prove causal mechanisms. Since the study population is from a single allergy clinic, this may lead to selection bias. However, clinical information was collected at the time of the clinic visit, thus reducing recall bias. The last limitation is the fact that the follow-up was done at 3 months after the initiation or the adjustment of the therapy, our plan is to extend the follow-up over a longer period.