Associations Between Asthma/Asthma Exacerbation and Previous Proton-Pump Inhibitor use: A Nested Case-Control Study using a National Health Screening Cohort


 Background: Proton-pump inhibitors (PPIs) block acid secretion from gastric parietal cells; however, recent studies have reported that PPIs have antioxidant and anti-inflammatory properties in various cells. Newer PPIs are stronger inhibitors of acid secretion; however, the anti-inflammatory effects of these drugs have not been assessed. We evaluated anti-inflammatory effect of PPIs on the development of asthma/asthma exacerbation (AE) in a national health screening cohort.Methods: This case-control study comprised 64,809 participants with asthma who were 1:1 matched with controls from the Korean National Health Insurance Service-Health Screening Cohort. Conditional logistic regression analysis was used to evaluate the effect of previous PPI use on an asthma diagnosis in all participants. Unconditional logistic regression was used to assess the effect of PPI use on AE in participants with asthma. These relationships were estimated in a subgroup analysis according to PPI generation.Results: Overall, PPI use increased the risk of asthma diagnosis (adjusted odds ratio [aOR]=1.29, 95% confidence interval [CI]=1.23-1.35, P<0.001). Use of the first-generation PPIs was associated with asthma (aOR=1.34, 95% CI=1.18-1.52, P<0.001), while use of 2nd-generation PPIs was not (aOR= 0.97, 95% CI=0.82-1.15, P=0.748). In contrast, overall PPI use decreased the risk of AE in participants with asthma (aOR=0.79, 95% CI=0.75-0.84, P<0.001), although this effect was observed only for 2nd-generation PPIs (aOR=0.76, 95% CI=0.65-0.89, P=0.001).Conclusions: PPI use increased the risk for subsequent asthma diagnosis. However, this effect was confined to first-generation PPIs. Second-generation PPIs decreased the risk of AE.


Background
Gastroesophageal re ux (GERD) and asthma, which are both common conditions, often coexist in the same patient. Estimates of the prevalence of GERD among patients with asthma have varied from 12.5-51.0% [1,2]. A signi cant association between re ux disease and exacerbations in asthmatic patients has been observed (odds ratio [OR] = 4.9 95% Con dence Interval [CI] = 1.4-17.8) [3,4]. Indeed, several randomized clinical trials (RCTs) have been performed to assess whether proton-pump inhibitors (PPIs) can improve asthma-related outcomes; however, there are some mixed ndings [5]. Patients with asthma who had a diagnosis of GERD showed improvement in peak expiratory ow rate and asthma-related quality of life scores but no signi cant bene t for asthma symptom scores and lung function [6][7][8]. Therefore, current asthma guidelines recommend that anti-re ux therapy should be recommended to patients with asthma having concomitant re ux symptoms [9].
PPIs are considered the most effective therapy for relieving GERD symptoms. PPIs block gastric acid secretion by inhibiting H+, K + ATPase of gastric parietal cells. Newer PPIs, such as esomeprazole, rabeprazole, and ilaprazole, known as 2nd -generation PPIs, are more stable, and their plasma concentration is not strongly in uenced by different cytochrome P450 enzyme activities; therefore, they are more potent at inhibiting acid secretion than rst-generation PPIs [10,11].
In addition, PPIs have anti-in ammatory properties that might prevent in ammation in PPI-responsive eosinophilic esophagitis (EoE) [12,13]. PPIs blocked the IL-4-and IL-13-stimulated increase in eotaxin mRNA and protein secretion through signal transducer and activator of transcription 6 (STAT6) in EoE [14]. In addition, PPIs reduce esophageal eosinophilia by restoring esophageal mucosal barrier integrity, which is important, as dilated intercellular spaces make the esophageal mucosa permeable to swallowed antigens linked to type 2 in ammation. Considering that sensitization to ingested or inhaled allergens is necessary for the development of EoE, which is a common pathogenic feature of allergic asthma, PPI use could prevent asthma development or improve asthma-related outcomes. Previous studies demonstrated that PPIs reduced IL-13-induced eotaxin-3 expression via non-gastric H and K-ATPase and that newer PPIs more strongly inhibited eotaxin-3 secretion, suggesting that the anti-type 2 effect was well correlated with the potency of individual PPIs [15,16].
Based on these ndings, we hypothesized that PPIs might be associated with a reduction in asthma diagnosis or AE in adulthood. To estimate the PPI effect on asthma diagnosis or asthma-related outcomes, we conducted a matched case-control study using a nationwide, population-based cohort in a Korean adult population. The primary objective was to estimate the association between PPI use and subsequent asthma diagnosis compared to that in control participants. We also analyzed the effect of PPIs on allergic asthma, as PPIs have anti-type 2 activities, and allergic asthma is a type 2-dominant in ammatory phenotype. The secondary objective was to evaluate the association between PPI use and AE compared to non-asthma exacerbation (NAE) among the participants with asthma. We further analyzed the effect of PPI generation on asthma diagnosis and AE to identify a relationship between acidsuppressive potency and the anti-in ammatory e cacy of PPIs.

Data source and ethical consideration
We used the Korean National Health Insurance Service-Health Screening Cohort (NHIS-NSC) data for this study; a comprehensive description of this cohort is provided elsewhere [17]. Brie y, these data constitute approximately a million participants, 2.2% of the total eligible population, who were randomly sampled from the 2002 and followed for 11 years, until 2013. These data include information about participants' demographics, health insurance claim codes, diagnostic codes, socio-economic status, and medical examination data. This study was approved by the Institutional Review Board (IRB) of Hallym University (IRB No: 2019-10-023), and the need for written informed consent was waived.

Participant selection
Among the 514,866 participants with 615,488,428 medical claim codes, participants were selected for the asthma group according to the de nition in our study (n = 81,106). Asthma was de ned if the participants from the cohort were diagnosed with asthma (J45, J46) based on the International Classi cation of Diseases, Tenth Revision (ICD-10). Among these individuals, we selected participants who were diagnosed with asthma more than two times by a physician and who were treated with asthma-related medications. Asthma medications include inhaled corticosteroids (ICS), ICS combined with long-acting β2-agonists (LABAs), short-acting β2-agonists (SABAs), systemic LABAs, leukotriene antagonists (LTRAs), xanthine derivatives, or systemic corticosteroids [18]. Participants in the asthma group who were diagnosed with asthma in 2002 were removed to select asthma participants diagnosed for the rst time (washout periods, n = 14,044). Other participants were selected for the control group (n = 433,760). In the control group, participants were excluded if they died before 2003 or had no records after 2003 (n = 34). In addition, the control participants were excluded if they were treated for J45 or J46 ICD-10 codes with no record of an asthma medication prescription (n = 108,730). Participants who were diagnosed with hiatal hernia, Zollinger-Ellison syndrome, systemic sclerosis, achalasia or pyloric obstruction, who underwent gastric surgery, and who had no record of total cholesterol/blood pressure/body mass index (BMI, kg/m 2 ) were excluded. The asthma participants were 1:1 matched with control participants for age, sex, income, and region of residence. To minimize selection bias, the control participants were selected with random number generation. The index date of each asthma participant was set as the time of treatment of asthma.
The index date for individual control participants was set as the index date of their matched asthma participant. Therefore, each matched asthma participant and control participant had the same index date. Using the above matching rules, 253,128 control participants were excluded and nally, 64,809 asthma participants were 1:1 matched with 64,809 control participants.
Proton-pump inhibitor (exposure) PPI users were de ned as participants who were prescribed PPIs within the previous year (365 days) before the index date. PPI users were classi ed into three categories as follows: (1) PPI prescription history, (2) the summation of PPI prescription dates, and (3) PPI prescription dates for each generation of PPIs.
Participants with a PPI prescription were grouped as current PPI users if they were prescribed PPIs within 30 days before the index date. If the participants were prescribed PPIs within 31 days to 365 days before the index date, they were grouped as past PPI users. Others were grouped as PPI non-users.
In the third category, the participants were recategorized into two categories according to the generations of PPIs [19]. The rst generation of PPIs consisted of pantoprazole, omeprazole, and lansoprazole. Second-generation PPIs were esomeprazole, dexlansoprazole, rabeprazole, and ilaprazole. PPI prescription dates were summed according to each generation of PPIs.

Asthma (outcome)
The asthma group included participants who were treated for asthma (ICD-10: J45) or status asthmaticus (J46) with asthma-related medications ≥ 2 times from 2002 through 2015. This de nition was adapted from that in a previously validated study [20].
Among the asthma participants, AE was de ned if asthma participants visited emergency medical doctors or had admissions that were not their rst visit for asthma [21]. Asthma participants who were prescribed steroids ≥ 20 mg a day ≥ 3 days within 2 weeks were also de ned as having AE [21].
Allergic asthma was de ned as having at least one of the following: 1) history of allergic rhinitis by ICD-10 code (J30) within 1 year or 2) therapy with oral antihistamines, leukotriene modi ers, intranasal corticosteroid spray, or intranasal antihistamines for ≥ 1 month within 1 year. All asthma patients who did not meet the de nition of allergic asthma were classi ed as having non-allergic asthma [22,23].
Based on the de nition above, asthma participants were classi ed into AE (n = 12,707) and NAE (n = 52,102) groups and allergic asthma (n = 18,194) and nonallergic asthma (n = 46,615) groups. The history of previous PPI prescription was analyzed for an association with asthma by comparing asthma patients to the controls, the AE group to the NAE group, and the allergic asthma group to the non-allergic asthma group (Fig. 1).
To evaluate the effects of PPI on AE, we set a new index date for AE and NAE. The new index date for AE was de ned as the rst exacerbation date. For NAE, a random date between the rst asthma onset and the last day of follow-up was selected.

Covariates
Age groups were divided into 5-year intervals, beginning at 40-44 years and ending at 85 + years [2]. Income groups were classi ed into 5 classes (class 1 [lowest income]-5 [highest income]). The area of residence was classi ed as urban/rural based on the de nitions in a previous study [2]. Tobacco smoking, alcohol consumption, and obesity according to BMI were categorized the same way as in our previous study [24].
Total cholesterol (mg/dL), systolic blood pressure (mmHg), diastolic blood pressure (mmHg), and fasting blood glucose (mg/dL) were measured. The Charlson Comorbidity Index (CCI) was applied excluding respiratory diseases. GERD and chronic obstructive pulmonary disease (COPD) were de ned as in our previous study [25]. Among GERD patients, GERD treatment within the 2 years (730 days) before the index date was quanti ed.
We summed each histamine-2 receptor antagonist (H2RA) and non-steroidal anti-in ammatory drug (NSAID) prescription date within a year (365 days) before the index date.

Statistical analyses
The demographic characteristics were compared between the asthma and control groups, and the differences were considered standardized difference (SDs).
To analyze the odds ratios (ORs) with 95% con dence intervals (CIs) of PPI prescription history for asthma, PPI prescription dates for asthma, and rst generation/second generation PPI prescription dates for asthma, conditional logistic regression was used. In these analyses, crude and adjusted models were strati ed for age, sex, income, and region of residence.
Regarding AE and allergic asthma, only asthma participants were included in the analyses. To analyze the odds ratios (ORs) with 95% con dence intervals (CIs) of PPI prescription history for AE/allergic asthma, PPI prescription dates for AE/allergic asthma, and rst generation/second generation PPI prescription dates for AE/allergic asthma, unconditional logistic regression was used. In these analyses, various adjusted models were calculated.
Subgroup analyses were performed for the sensitivity analysis. In this study, we divided participants by age (< 60 years old and ≥ 60 years old), sex (males and females), income (low income and high income), and region of residence (urban and rural). SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) was used for the statistical analysis. We performed two-tailed analyses, and a P value of < 0.05 was considered statistically signi cant.
Among the 64,809 participants with asthma, 19.6% (n = 12,707) comprised the AE group, while the remaining patients (n = 52,102) comprised the NAE group.

The association between PPI use and asthma diagnosis
The numbers of current and past PPI users were higher among participants with asthma than among controls (3.2%/1.9% for current PPI users: 10.4%/7.3% for past PPI users, Table 1). The previous history of PPI prescription was related to asthma diagnosis in both current and past PPI users (P < 0.001, Table 2). Regardless of the cumulative prescription days of PPIs, the OR for asthma was signi cantly increased in all models (P < 0.001). Abbreviations: CCI, Charlson comorbidity index; COPD, chronic obstructive pulmonary disease; DBP, diastolic blood pressure; GERD, gastroesophageal re ux disease; NSAID, non-steroidal anti-in ammatory drug; PPI, proton-pump inhibitor; SBP, systolic blood pressure generation PPIs and an allergic asthma diagnosis (OR = 0.97, 95% CI = 0.78-1.21, P = 0.769 for ≥ 90 days in model 7). Abbreviations: CCI, Charlson comorbidity index; COPD, chronic obstructive pulmonary disease; DBP, diastolic blood pressure; GERD, gastroesophageal re ux disease; NSAID, non-steroidal anti-in ammatory drug; PPI, proton-pump inhibitor; SBP, systolic blood pressure This study found that previous and current PPI use was associated with incident asthma in a Korean adult population. However, However, PPI use decreased AE de ned by oral steroid bursts, ER visits, or hospitalizations, among the participants with asthma. Subgroup analyses showed that the association between PPIs and asthma/AE was different according to PPI generation. Only rst-generation PPIs were associated with an increased risk for asthma diagnosis, and 2nd-generation PPIs were associated with a decreased risk for AE among participants with asthma.
Previous association studies were primarily performed in children whose mothers used PPIs and/or H2RAs during pregnancy, causing their offspring to develop asthma. Meta-analyses have revealed an increased risk of asthma development in childhood with the use of any acid-suppressive medications (relative risk =  [27]. In the adult population, only one study investigated the association between asthma incidence and PPI use ≥ 90 days, and the overall incidence of asthma was greater in the PPI cohort than in the non-PPI cohort (HR = 1.76, 95% CI = 1.64-1.88) [28]. Our study found that PPI use increased the risk for subsequent asthma diagnosis, with an OR of 1.43; however, this association was observed with only rst-generation PPIs.
One postulated mechanism linking PPI use to asthma development is that PPIs could cause imbalance in symbiotic and pathological gut species. For infants or children, a greater abundance of a speci c bacterium or reduced bacterial diversity was associated with the development of allergic diseases [29]. A prospective study in children showed that PPI treatment induced dysbiosis and bacterial overgrowth, suggesting that PPI use could cause dysbiosis in the gut. This change may promote type 2 in ammation in the immune system [30]. An adult population-based cohort study demonstrated a lower abundance of gut commensals and lower microbial diversity in PPI users than in PPI non-users [31]. However, none of these studies provided direct evidence that PPIs were associated with asthma development. Therefore, further epidemiologic, and mechanistic evidence is essential to support the link between the PPI effect on the gut microbiome and subsequent asthma development, considering different PPIs, doses, and durations in childhood and adulthood.
In this study, previous PPI use decreased the risk of AE in participants with asthma, which was greater in participants who took PPIs for ≥ 90 days (OR = 0.81, 95%CI = 0.73-0.90). A potential mechanism for the protective effect of PPIs against AE might be their anti-type 2 or anti-in ammatory action. PPIs signi cantly inhibited IL-13-induced eotaxin-3 expression in nasal epithelium, and patients with chronic rhinosinusitis (CRS) taking PPIs showed lower in vivo eotaxin-3 levels than those not taking PPIs [15]. In addition, PPIs favorably control the oxidant-antioxidant system by scavenging reactive oxygen species in airways [32][33][34]. Recent transcriptomic data demonstrated that PPIs exert pharmacological actions in regulating immune, vascular endothelial, and airway epithelial biology; they do not just hinder the nal-step of IL-13 induced in ammatory responses [12,35]. Therefore, we postulated that the decreased OR for AE in PPI users could be due to the pleiotropic and anti-type 2 properties of PPIs.
This study found that PPI effects on asthma or AE differed according to the generation of the drug. Second-generation PPIs signi cantly decreased the diagnosis of allergic asthma with an OR of 0.87-0.89 and were associated with a decrease in AE (OR = 0.76, 95%CI = 0.65-0.89, ≥ 90 days), indicating that PPIs, especially 2nd generation, might be bene cial for allergic asthma or AE, which has a type 2 in ammatory milieu. Pharmacokinetic studies showed that 2nd-generation PPIs were more effective in suppressing gastric acid secretion because they rapidly converted to the active metabolite sulfenamide and had better reactivity with cysteines in H+, K + ATPase on gastric parietal cells [10,36]. An adult population study showed that rabeprazole did not increase the risk of asthma (aHR = 1.04, 95% CI = 0.94-1.15) compared to rst-generation PPIs (aHR = 1.38, 95% CI = 1.26-1.50 for omeprazole; aHR = 1.15, 95% CI = 1.04-1.24 for pantoprazole) [28]. The latest transcriptome data in EoE revealed that substantial overlap was observed in gene expression with omeprazole and esomeprazole treatment [37]. However, esomeprazole induced more signi cant changes in gene expression than omeprazole, suggesting that individual PPIs may have different effects on in ammation and homeostasis in airways. These mechanistic and epidemiological data could partly explain our main results.
This study has some limitations. First, this study used health insurance data; therefore, we applied an operational de nition of asthma/AE, which is not as accurate as the de nitions in RCTs and registry-based studies. Second, we used prescription days, but actual drug exposure could not be monitored in this study. Third, we adjusted for several variables related to PPI use to minimize confounding effects between PPIs and asthma/AE; however, as it had a retrospective-design, unmeasured confounding effects could not be excluded. Fourth, our data were somewhat different from the results of an already published RCT, where there was no bene t of PPIs were found in asthma patients with asymptomatic GERD [8]. However, the current study demonstrated that regardless of GERD status, PPI use decreased AE in participants with asthma.
This study has the following strengths. First, we included a large population of participants treated with PPIs, with ample statistical power in the primary analysis. Second, we adjusted for variables related to PPI use or asthma, such as NSAID or H2RA prescriptions, obesity, GERD, and COPD. Third, we analyzed PPI use and AE in participants with asthma, which has not been done in other studies. We found that 2nd-generation PPIs were associated with a decreased risk of AE, in accord with recent research da ta on anti-in ammatory effects and PPIs.

Conclusions
In this study, we found that PPI use was associated with an increased risk of asthma. However, this effect was con ned to rst-generation PPIs. Secondgeneration PPIs decreased the risk of AE in participants with asthma. waived as all participants data were obtained in an anonymous manner.

Consent for publication
Not applicable.

Availability of data and materials
The datasets generated and analysed during the current study are not publicly available due to the need for approval from the Korean national health insurance service committee, but they are available from the corresponding author on reasonable request. Figure 1 A schematic illustration of the participant selection process that was used in the present study. Of 514,866 participants, 64,809 asthma participants were matched with the same number of control participants for age, sex, income, and region of residence.

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