You are here

Article Text

Article menu
Chronic obstructive pulmonary disease
Original article
The relationship between Helicobacter pylori seropositivity and COPD
Free
  1. Marc A Sze1,
  2. Yu-Wei Roy Chen1,
  3. Sheena Tam1,
  4. Donald Tashkin2,
  5. Robert A Wise3,
  6. John E Connett4,
  7. SF Paul Man1,
  8. Don D Sin1
  1. 1Department of Medicine (Division of Respiratory Medicine), Centre for Heart Lung Innovation, Providence Heart/Lung Institute at St Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
  2. 2Division of Pulmonary and Critical Care Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
  3. 3Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
  4. 4Division of Biostatistics, University of Minnesota School of Public Health, Minneapolis, Minnesota, USA
  1. Correspondence to Dr Don D Sin, Room 166-1081 Burrard Street, Vancouver, BC, Canada V6Z 1Y6; Don.Sin{at}hli.ubc.ca

Abstract

Rationale Chronic systemic infections such as those with Helicobacter pylori (H. pylori) may contribute to the evolution and progression of chronic obstructive pulmonary disease (COPD). Using data from the Lung Health Study (LHS), we determined the relationship of H. pylori infection with the severity and progression of COPD.

Methods Using an immunoassay, we measured H. pylori immunoglobulin G (IgG) antibody titres in serum samples of 4765 patients with mild-to-moderate COPD. We then determined their relationship with the individual's FEV1 and the rate of decline in FEV1 and mortality over 11 years using multiple regression analysis.

Results Approximately 18% of the patients were seropositive to H. pylori and these individuals demonstrated lower FEV1 (L) values at every study visit compared with individuals who were seronegative for H. pylori (p value=0.00012). However, patients with seropositivity to H. pylori were on average 0.012 m shorter than those with seronegativity (p value=0.0015). The significant relationship between FEV1 and H. pylori seropositivity disappeared when FEV1 per cent predicted (FEV1pp) was used (p value=0.45). H. pylori seropositive individuals had greater circulating C reactive protein (CRP) levels compared with H. pylori seronegative individuals (p value=0.012), and had increased risk of cardiovascular mortality (relative risk 1.61, p=0.05).

Conclusions H. pylori infection was associated with reduced lung function that is most likely due to the effect of the bacterium on lung growth earlier in life. It is also associated with systemic inflammation and increased risk of cardiovascular mortality in patients with COPD.

Trial registration numbers NCT00000568 and NCT00000569.

  • COPD epidemiology
  • Respiratory Infection

https://doi.org/10.1136/thoraxjnl-2015-207059

Statistics from Altmetric.com

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

    Key messages

    What is the key question?

    • Can Helicobacter pylori infection lead to reduced lung function and/or poor clinical outcomes in patients with mild-to-moderate COPD?

    What is the bottom line?

    • Patients with H. pylori infection have lower FEV1 (L), are shorter on average, have higher circulating C reactive protein (CRP) levels and may be at increased risk of cardiovascular death compared with patients without H. pylori.

    Why read on?

    • This is the largest study to date, with over 4000 patients, to investigate the possible role of H. pylori infection in the systemic inflammatory response and poor health outcomes in COPD.

    Introduction

    Chronic obstructive pulmonary disease (COPD) is a major disease burden across the world, affecting 300–600 million individuals and killing 3 million annually.1 Although the pathogenesis of COPD has not been fully worked out, chronic inflammation is believed to be an important component. In addition to lung inflammation, some individuals with COPD demonstrate persistent systemic inflammation, which is associated with increased symptoms and poor health outcomes, including hospitalisation and mortality.2 A major source of persistent systemic inflammation is the gastrointestinal tract, which through the actions of the local bacterial microbiota modulates the body's immune response to viral infections.3 Consistent with this theory, a recent study has shown that manipulation of the gut microbiota with antimicrobials early in the lifespan of ‘asthmatic’ mice alters their disease phenotype.4

    One important bacterial player in the gastrointestinal tract is Helicobacter pylori (H. pylori). Previous studies suggest that chronic infection with H. pylori is associated with persistent systemic inflammation and endothelial dysfunction, which are also found in patients with COPD.5 Moreover, large epidemiological studies have shown that patients with COPD have significantly increased risk of peptic ulcers compared with ‘healthy’ smokers.5

    There have been prior studies that have investigated a potential role of H. pylori infection in COPD.6 ,7 However, these studies have produced discrepant findings probably owing to small sample sizes and selection bias. Using a large cohort of patients with mild-to-moderate COPD, we determined the relationship of H. pylori infection with clinically relevant endpoints in COPD such as lung function, lung function decline and mortality over time.

    Methods

    Sample population

    We used data and samples from the Lung Health Study (LHS), which has been described in detail previously.2 In brief, LHS recruited smokers between the ages of 35 and 60 years who had Global initiative for chronic Obstructive Lung Disease (GOLD) 1 to GOLD 2 grades of COPD, defined by spirometry. Individuals who had other major diseases, such as cancer, were excluded. Once enrolled, patients were asked to visit the study centre annually for 5 years. At these visits, salivary cotinine levels and exhaled carbon monoxide levels were measured to validate the smoking status of the patients and to objectively verify if they had quit smoking. Detailed information on the study population can be found in previously published reports.2 ,8 This study analysed data on 4765 patients from this cohort.

    Blood collection and ELISA measurements

    At the 5-year follow-up visit, participants were asked for a blood sample. Blood samples from those who consented were separated into their respective components, transferred to the LHS main coordinating centre and stored in −70°C freezers. Serum samples were thawed, and H. pylori immunoglobulin G (IgG) concentrations were measured using a commercially available ELISA kit (DRG Diagnostics, GmbH, Marburg, Germany) according to the manufacturer's protocol. The lower limit of a positive H. pylori IgG titre, indicative of colonisation, was 18 DU/mL. Values lower than 18 DU/mL were treated as not having an active H. pylori colonisation of the stomach. C reactive protein (CRP) was measured using a commercially available ELISA kit (Alpha Diagnostic, San Antonio, Texas, USA). The results from the CRP measurement have previously been reported.2 The protocols for blood collection were approved by the University of British Columbia/Providence Health Care Research Ethics Committee.

    Lung function measurements

    Spirometry was performed at recruitment and annually for 5 years. One final measurement was then made approximately 11 years following initial recruitment. Owing to the smoking cessation intervention and the use of an active bronchodilating agent, certain patients experienced a significant increase in lung function in the first 2 years,9 after which, these individuals experienced a linear rate of FEV1 decline.10 For the present analysis, measurements taken after year 1 were considered baseline. For analysis on rapid decliners, a range of cut-off values (20 –160 mL/year) in 20 mL/year increments were used as thresholds, and those below the cut-off were categorised as steady decliners or non-decliners, and those above the cut-off were categorised as rapid decliners. We also determined total mortality and disease-specific mortality (lung cancer, congestive heart disease and cardiovascular disease) in this cohort as previously described.8

    Statistical analysis

    All statistical analyses were performed using R (V.3.1.2) and R Studio (V.0.98.1091). The study population was first divided into those who were H. pylori IgG seropositive and those who were seronegative. Analysis was performed either on FEV1 (L) or FEV1 per cent predicted (FEV1pp) from year 2 to year 11. For both analyses, a t test was used to determine significance of changes between those with and without positive antibodies to H. pylori at each time point. All of these p values were corrected for multiple comparisons using the Bonferroni method. We then performed a similar analysis among patients in GOLD grade 1 and 2, separately. We compared the prevalence of H. pylori IgG seropositivity between GOLD grade 1 and 2 using a χ2 test. Linear regression analysis was used to evaluate the relationship between serum H. pylori IgG levels and decline in FEV1 (L) or FEV1pp. Patient characteristics between the H. pylori positive and negative groups were compared using t tests for continuous variables and a χ2 test for dichotomous variables. χ2 testing was used to compare the H. pylori prevalence between rapid and steady decliners. For values that fell in the ‘grey’ zone of positivity (H. pylori IgG levels between 15 and 18 DU/mL), the samples were considered equivocal for infectivity (see online supplementary figure S1). Since the equivocal group mirrored the negative group, we combined these two groups for all analyses. There was no significant variation in data across the ELISA plates (see online supplementary figure S2). Multiple linear regression models were used to adjust for sex, smoking status, race, body mass index (BMI) and height. The risks of total mortality and disease-specific mortality between H. pylori seropositive and seronegative patients were compared using a χ2 test. The difference in CRP levels between H. pylori positive and negative patients was compared using a t test, following log-transformation of CRP values.

    Results

    H. pylori positive and negative patient characteristics

    An overview of the patient characteristics can be found in online supplementary table S1, and these characteristics based on H. pylori seropositivity are summarised in table 1. There was no difference in sex, age at which smoking started, pack years, BMI, race or the number of sustained quitters between the H. pylori seropositive and seronegative groups (p value >0.05). However, there was a significant height difference between the H. pylori positive and negative groups (p value=0.0015). The H. pylori positive group was on average approximately 0.012 m shorter than the H. pylori negative group (table 1). The relative risk (RR) of mortality along with the 95% CI can be found in table 2. Individuals with H. pylori seropositivity had a borderline significant increase in the risk of cardiovascular deaths (RR=1.61, p value=0.05). However, there was no significant difference in total or lung-specific mortality between the two groups. Patients with H. pylori seropositivity demonstrated higher serum CRP levels (1.063±0.714 mg/L vs 0.995±0.689 mg/L in logarithmic scale, p value=0.012).

    View this table:
    Table 1

    Patient characteristics of the Helicobacter pylori positive and negative groups

    View this table:
    Table 2

    Relative risk (RR) breakdown based on Helicobacter pylori seropositivity

    Overall lung function decline and H. pylori seropositivity

    Patients who were H. pylori positive demonstrated reduced FEV1 (L) at baseline compared with those who were negative (p value=6.48×10−6) (figure 1A). Men and women with seropositivity to H. pylori had lower FEV1 (L) than their H. pylori negative counterparts except for men at year 11 (see online supplementary figures S3 and S4). However, there were no differences in the rate of decline (slope) between the two groups (p value=0.35). The baseline FEV1pp values, which corrected for age, race, sex and height, were not significantly different between the groups (p value=0.45) (see online supplementary figures S5 and S6). Similarly, the rate of decline was not significantly different between the two groups (p value=0.67) (figure 1B). Although there was a significant inverse relationship between serum H. pylori IgG concentrations (in a natural log scale) and FEV1 (L) (p value=2.9×10−7), this relationship disappeared when FEV1pp was used in lieu of FEV1 (L) (p value=0.68). There was no significant difference in the risk of H. pylori seropositivity between rapid and slow decliners (average p value=0.31), irrespective of the threshold value employed to define rapid decliners (data not shown).

    Figure 1
    Figure 1

    (A) Mean FEV1 (L) over 11 years according to Helicobacter pylori status. There was no significant difference in the slope of the two lines (p>0.05). However, at every measured time point, those with H. pylori had significantly lower FEV1 after Bonferroni correction (p value <0.009). (B) Mean FEV1 per cent predicted (FEV1pp) over 11 years according to H. pylori status. There was no significant difference in both the slope and mean FEV1pp measured between the two groups (p>0.05).

    H. pylori seropositivity and socioeconomic status of patients

    To determine the potential influence of socioeconomic status (SES) on H. pylori seropositivity, we evaluated two variables related to SES of the LHS patients: maximal educational attainment11 and median income level at the time of study enrolment.12 Patients who were seropositive to H. pylori had on average 1 year of less schooling and approximately US$3000 less median income than those who were seronegative to H. pylori (table 1). There was also a significant difference in both median income and years of education between the H. pylori seropositive and seronegative groups (p<0.00001) (table 1). To determine the impact of these SES variables on the adult height of these study participants, we constructed a multivariable linear regression model in which the dependent variable was height (in metres), and the independent variables were age, sex, H. pylori serum concentration, median income and maximal years of education achieved (see online supplementary table S2). We found that the educational variable, but not median income, was strongly related to adult height. Interestingly, inclusion of educational attainment variable into the model made the H. pylori concentrations no longer significantly related to the adult height of the study participants. Together, these data suggest that years of education (a proxy for SES during childhood11) are strongly related to H. pylori status and are likely a part of the causal pathway in determining adult height.

    Mild GOLD grade and H. pylori seropositivity

    There was no significant difference in H. pylori seropositivity between patients with GOLD 1 and GOLD 2 severity (17.5% and 17.7%, respectively). Patients with GOLD 1, who were H. pylori seropositive, demonstrated lower lung function at every visit compared with seronegative patients (average p value=0.011) (figure 2A). In contrast, for GOLD 2 grade, there was no significant difference in FEV1 between H. pylori seropositive and seronegative individuals (average p value= 0.42) (figure 2B). There was no difference in H. pylori IgG antibody concentration between GOLD 1 and GOLD 2 grade of disease (38.1±111.0 and 38.3±102.2 DU/mL, respectively). There was a significant difference in height between the GOLD 1 H. pylori positive and negative groups (p=0.0029, 1.714±0.09 m and 1.729±0.089 m, respectively). No significant difference in height was found in the GOLD 2 group based on H. pylori seropositivity (p=0.0742, H. pylori positive=1.707±0.084 m, H. pylori negative=1.715±0.089 m).

    Figure 2
    Figure 2

    (A) Linear regression of the natural log of measured Helicobacter pylori immunoglobulin G (IgG) antibodies versus FEV1 (L). A significant negative correlation was found (R2=0.0054, slope=−0.18, p value=2.9×10−7). (B) Linear regression of the natural log of measured H. pylori IgG antibodies versus FEV1 per cent predicted (FEV1pp). No relationship was found between these two variables (R2=0.0002, slope=−0.0009, p value=0.68).

    Discussion

    The present study is the largest of its kind to evaluate the possible impact of H. pylori infection in patients with COPD. In this cohort, we found that H. pylori infection is relatively common in patients with COPD (approximately 18%) and is associated with systemic inflammation. Importantly, although H. pylori infection does not modify rate of decline in FEV1 over time or respiratory-specific mortality, it increases the risk of cardiovascular deaths, which is the major source of mortality in patients with mild-to-moderate COPD.

    Interestingly, we also found that H. pylori infection was associated with reduced adult height. Height has long been known to be a major predictor of absolute lung volume.13 Because of this, FEV1 is height dependent.14 In the present study, the mean difference in height between the seropositive and seronegative individuals was 0.012 m. Our data are in keeping with a large body of literature demonstrating that chronic infection with this bacterium impairs growth during childhood, which manifests as shorter adult height.15 ,16 One study found that the average difference in height between H. pylori positive and negative individuals was 0.035 m.16 Interestingly, another study found that the growth rate in children could be restored on eradication of H. pylori infection with antibiotics.17 The mechanism by which H. pylori stunts the growth velocity in children is not fully known, and is an active area of investigation. We postulate that chronic infection with H. pylori in childhood may have caused impaired growth in lungs, leading to increased risk of COPD in adulthood. However, persistence of infection in adulthood probably does not accelerate progression of COPD. These findings add support to the hypothesis that early-life exposures can have a critical role to play in lung development and overall lung function.18 This hypothesis will need to be tested in a longitudinal cohort with robust follow-up.

    Our data support the hypothesis that H. pylori could contribute to systemic inflammation in COPD19 by showing that CRP was elevated in the seropositive group (table 1). Additionally, previous studies have shown that those with H. pylori seropositivity are at an increased risk of myocardial infarction or coronary heart disease.19 ,20 Consistent with these prior observations, we found that those with H. pylori seropositivity had an increased risk of cardiovascular death, albeit at a borderline statistical significance (table 2). However, there were no significant differences in total or respiratory-specific mortality between H. pylori seropositive and H. pylori seronegative patients (table 2). Together, our data support the notion that H. pylori seropositivity is associated with systemic inflammation, and this in turn could lead to increased risk of cardiovascular events in patients with mild-to-moderate COPD.

    Although there was no difference in the overall distribution of H. pylori seropositivity between individuals in GOLD 1 and 2 grades, there was a difference in FEV1 (L) at all time points between seropositive and seronegative patients in GOLD 1, but not in GOLD 2 (figure 3). The reason for this observation is not entirely clear. However, there was a significant difference in height in the GOLD 1 group between H. pylori seropositive and seronegative individuals that was not observed in the GOLD 2 group. Additionally, it is notable that the slope of FEV1 decline decreased from GOLD 1 to GOLD 2,21 which may have obscured the small influence of H. pylori on the rate of decline (figure 3B).

    Figure 3
    Figure 3

    (A) Mean FEV1 (L) over 11 years in GOLD 1 for Helicobacter pylori positive and negative groups. No difference in slope was observed (p>0.05); however, at every year, except year 11, the mean FEV1 (L) was lower in the H. pylori positive group versus the negative group (p<0.005). (B) Mean FEV1 (L) over 11 years in GOLD 2 for H. pylori positive and negative groups. No difference was observed between slope and mean FEV1 between the two groups (p>0.05).

    There were limitations to the study. First, owing to the high percentage of Caucasians in the study population, the findings of the present study may not be generalisable to other racial groups. Second, we did not have sufficient ability to fully assess the SES of individuals in this study. Previous studies have shown that H. pylori may be linked to SES,22 ,23 and in turn, this could affect adult height. In the present study, we used years of education achieved as a surrogate for childhood SES11 and median income at study enrolment as a surrogate for adult SES.12 These are imperfect measurements of SES. Nevertheless, even using these imprecise SES measurements, we found a strong relationship of these variables with H. pylori status. Most importantly, we found that years of education achieved, but not median income, were significantly related to adult height, and the inclusion of the former variable into a multivariable model made the relationship between H. pylori status and adult height no longer significant. Collectively, these data are consistent with the notion that childhood SES is an important determinant of adult height and that H. pylori status may be in this causal pathway. Further work will be needed to validate this hypothesis. Third, this population was composed of patients with mild and moderate COPD, and it is possible that H. pylori may have a greater role in more severe disease. Fourth, LHS was conducted prior to the widespread availability of antimicrobial treatment for H. pylori, and as such, we could not determine the effects of eradication on lung function decline over time. However, our findings raise the tantalising possibility that early eradication (in childhood) may enable full development of lungs and reduce the risk of COPD later on in life. Fifth, because we do not have serial blood samples, we cannot be certain when patients were first infected with the bacterium. However, prior epidemiological data suggest that most infections occur during the first 5 years of life.24 Thus, seropositivity likely represents childhood infections. Sixth, past antibiotic use could have biased findings towards the null value. It has been well documented that antibiotic treatment to eradicate H. pylori can reduce H. pylori IgG levels.25–27 However, even targeted treatment with triple therapy, depending on country, can have a range of successful eradication rates (20%–80%).28 Furthermore, only specific antibiotics can be used to eradicate H. pylori due to the acidity of the environment in which it lives.28 Because LHS was conducted before the widespread use of triple therapy for H. pylori eradication, we believe that prior antibiotic use probably did not have a major impact on the findings. We also could not determine whether the presence of H. pylori represented active infection or colonisation. However, H. pylori is considered a pathogen and not a normal commensal in the gastrointestinal tract, and 75% of completely asymptomatic individuals harbouring H. pylori can demonstrate active gastritis on biopsy.29 Finally, in the present study, we did not evaluate the relationship of specific strains of H. pylori with clinical outcomes in COPD (eg, CagA). The relationship of specific strains of H. pylori with adverse health outcomes outside of the gastrointestinal tract is complex and controversial, with some studies showing a significant relationship with poor health outcomes30 ,31 while others showing a null or even a beneficial association.32–34 It was beyond the purview of this study to interrogate this complex interaction between specific strains of H. pylori and clinical outcomes in COPD.

    Notwithstanding these limitations, the present study resolves the ongoing controversy of the possible role of persistent H. pylori infection in the progression of COPD. Our data suggest that H. pylori infection in adulthood does not impact on rate of decline in FEV1. However, it may play a significant role in adult height, which may result in lower FEV1 (L) in adulthood, predisposing certain individuals to COPD later on in life. Our data support the hypothesis that early-life exposures can play a big role in lung function, and that at this early stage in life, environmental exposures can drastically impact later health. Further, our findings suggest that H. pylori infection may contribute to persistent systemic inflammation in some patients with COPD and to their increased risk of cardiovascular mortality.

    References

    1. ↵
      1. Mathers CD,
      2. Loncar D
      . Projections of global mortality and burden of disease from 2002 to 2030. PLoS Med 2006;3:e442. doi:10.1371/journal.pmed.0030442
      OpenUrlCrossRefPubMed
    2. ↵
      1. Man SF,
      2. Connett JE,
      3. Anthonisen NR, et al
      . C-reactive protein and mortality in mild to moderate chronic obstructive pulmonary disease. Thorax 2006;61:849–53. doi:10.1136/thx.2006.059808
      OpenUrlAbstract/FREE Full Text
    3. ↵
      1. Ichinohe T,
      2. Pang IK,
      3. Kumamoto Y, et al
      . Microbiota regulates immune defense against respiratory tract influenza A virus infection. Proc Natl Acad Sci USA 2011;108:5354–9. doi:10.1073/pnas.1019378108
      OpenUrlAbstract/FREE Full Text
    4. ↵
      1. Russell SL,
      2. Gold MJ,
      3. Hartmann M, et al
      . Early life antibiotic-driven changes in microbiota enhance susceptibility to allergic asthma. EMBO Rep 2012;13:440–7. doi:10.1038/embor.2012.32
      OpenUrlAbstract/FREE Full Text
    5. ↵
      1. Baty F,
      2. Putora PM,
      3. Isenring B, et al
      . Comorbidities and burden of COPD: a population based case-control study. PLoS One 2013;8:e63285. doi:10.1371/journal.pone.0063285
      OpenUrlCrossRefPubMed
    6. ↵
      1. Gencer M,
      2. Ceylan E,
      3. Yildiz Zeyrek F, et al
      . Helicobacter pylori seroprevalence in patients with chronic obstructive pulmonary disease and its relation to pulmonary function tests. Respiration 2007;74:170–5. doi:10.1159/000090158
      OpenUrlCrossRefPubMedWeb of Science
    7. ↵
      1. Siva R,
      2. Birring SS,
      3. Berry M, et al
      . Peptic ulceration, Helicobacter pylori seropositivity and chronic obstructive pulmonary disease. Respirology 2013;18:728–31. doi:10.1111/resp.12075
      OpenUrlCrossRefPubMed
    8. ↵
      1. Anthonisen NR,
      2. Skeans MA,
      3. Wise RA, et al
      . The effects of a smoking cessation intervention on 14.5-year mortality: a randomized clinical trial. Ann Intern Med 2005;142:233–9. doi:10.7326/0003-4819-142-4-200502150-00005
    9. ↵
      1. Anthonisen NR,
      2. Connett JE,
      3. Kiley JP, et al
      . Effects of smoking intervention and the use of an inhaled anticholinergic bronchodilator on the rate of decline of FEV1. The Lung Health Study. JAMA 1994;272:1497–505. doi:10.1001/jama.1994.03520190043033
      OpenUrlCrossRefPubMedWeb of Science
    10. ↵
      1. Anthonisen NR,
      2. Connett JE,
      3. Murray RP
      . Smoking and lung function of Lung Health Study participants after 11 years. Am J Respir Crit Care Med 2002;166:675–9. doi:10.1164/rccm.2112096
    11. ↵
      1. Perry E,
      2. Francis B
      . The social class gap for educational achievement: a review of the literature. RSA Projects, 2010. https://www.thersa.org/discover/publications-and-articles/reports/the-social-class-gap-for-educational-achievement-a-review-of-the-literature/Download (accessed 23 Apr 2015).
    12. ↵
      1. Bach PB,
      2. Guadagnoli E,
      3. Schrag D, et al
      . Patient demographic and socioeconomic characteristics in the SEER-Medicare database applications and limitations. Med Care 2002;40(8 Suppl):IV-19-25.
      OpenUrl
    13. ↵
      1. Hepper NG,
      2. Fowler WS,
      3. Helmholz HF Jr.
      . Relationship of height to lung volume in healthy men. Dis Chest 1960;37:314–20. doi:10.1378/chest.37.3.314
      OpenUrlCrossRefPubMedWeb of Science
    14. ↵
      1. Jedrychowski W,
      2. Ksiezyk M
      . Indices of ventilatory lung function (FVC, FEV1, FEV %) which adjust for age and height. Br J Prev Soc Med 1973;27:121–5.
      OpenUrlPubMed
    15. ↵
      1. Gulcan M,
      2. Ozen A,
      3. Karatepe HO, et al
      . Impact of H. pylori on growth: is the infection or mucosal disease related to growth impairment? Dig Dis Sci 2010;55:2878–86. doi:10.1007/s10620-009-1091-y
      OpenUrlCrossRefPubMed
    16. ↵
      1. Moayyedi P,
      2. Forman D,
      3. Duffett S, et al
      . Association between Helicobacter pylori infection and adult height. Eur J Epidemiol 2005;20:455–65. doi:10.1007/s10654-004-6634-0
      OpenUrlCrossRefPubMed
    17. ↵
      1. Yang YJ,
      2. Sheu BS,
      3. Yang HB, et al
      . Eradication of Helicobacter pylori increases childhood growth and serum acylated ghrelin levels. World J Gastroenterol 2012;18:2674–81. doi:10.3748/wjg.v18.i21.2674
      OpenUrlCrossRefPubMed
    18. ↵
      1. Nakagawa H,
      2. Tamura T,
      3. Mitsuda Y, et al
      . Significant association between serum interleukin-6 and Helicobacter pylori antibody levels among H. pylori-positive Japanese adults. Mediators Inflamm 2013;2013:142358. doi:10.1155/2013/142358
      OpenUrlPubMed
    19. ↵
      1. Liu J,
      2. Wang F,
      3. Shi S
      . Helicobacter pylori infection increase the risk of myocardial infarction: a meta-analysis of 26 studies involving more than 20,000 participants. Helicobacter 2015;20:176–83. doi:10.1111/hel.12188
      OpenUrlCrossRefPubMed
    20. ↵
      1. Mendall MA,
      2. Goggin PM,
      3. Molineaux N, et al
      . Relation of Helicobacter pylori infection and coronary heart disease. Br Heart J 1994;71:437–9. doi:10.1136/hrt.71.5.437
      OpenUrlAbstract/FREE Full Text
    21. ↵
      1. Vestbo J,
      2. Edwards LD,
      3. Scanlon PD, et al
      . Changes in forced expiratory volume in 1 second over time in COPD. N Engl J Med 2011;365:1184–92. doi:10.1056/NEJMoa1105482
      OpenUrlCrossRefPubMedWeb of Science
    22. ↵
      1. Etukudo OM,
      2. Ikpeme EE,
      3. Ekanem EE
      . Seroepidemiology of Helicobacter pylori infection among children seen in a tertiary hospital in Uyo, southern Nigeria. Pan Afr Med J 2012;12:39.
      OpenUrlPubMed
    23. ↵
      1. Malcolm CA,
      2. MacKay WG,
      3. Shepherd A, et al
      . Helicobacter pylori in children is strongly associated with poverty. Scott Med J 2004;49:136–8.
      OpenUrlAbstract/FREE Full Text
    24. ↵
      1. Fiedorek SC,
      2. Malaty HM,
      3. Evans DL, et al
      . Factors influencing the epidemiology of Helicobacter pylori infection in children. Pediatrics 1991;88:578–82.
      OpenUrlAbstract/FREE Full Text
    25. ↵
      1. Vonkeman HE,
      2. Deleest H,
      3. van Delaar M, et al
      . Assessment of Helicobacter pylori eradication in patients on NSAID treatment. BMC Gastroenterol 2012;12:133. doi:10.1186/1471-230X-12-133
      OpenUrlCrossRefPubMed
    26. ↵
      1. Kato S,
      2. Furuyama N,
      3. Ozawa K, et al
      . Long-term follow-up study of serum immunoglobulin G and immunoglobulin A antibodies after Helicobacter pylori eradication. Pediatrics 1999;104:e22. doi:10.1542/peds.104.2.e22
      OpenUrlAbstract/FREE Full Text
    27. ↵
      1. Feldman M,
      2. Cryer B,
      3. Lee E, et al
      . Role of seroconversion in confirming cure of Helicobacter pylori infection. JAMA 1998;280:363–5. doi:10.1001/jama.280.4.363
      OpenUrlCrossRefPubMedWeb of Science
    28. ↵
      1. Lopes D,
      2. Nunes C,
      3. Martins MC, et al
      . Eradication of Helicobacter pylori: past, present and future. J Control Release 2014;189:169–86. doi:10.1016/j.jconrel.2014.06.020
      OpenUrlCrossRefPubMed
    29. ↵
      1. Dooley CP,
      2. Cohen H,
      3. Fitzgibbons PL, et al
      . Prevalence of Helicobacter pylori infection and histologic gastritis in asymptomatic persons. N Engl J Med 1989;321:1562–6. doi:10.1056/NEJM198912073212302
      OpenUrlCrossRefPubMedWeb of Science
    30. ↵
      1. Pietroiusti A,
      2. Diomedi M,
      3. Silvestrini M, et al
      . Cytotoxin-associated gene-A—positive Helicobacter pylori strains are associated with atherosclerotic stroke. Circulation 2002;106:580–4. doi:10.1161/01.CIR.0000023894.10871.2F
      OpenUrlAbstract/FREE Full Text
    31. ↵
      1. Mayr M,
      2. Kiechl S,
      3. Mendall MA, et al
      . Increased risk of atherosclerosis is confined to CagA-positive Helicobacter pylori strains: prospective results from the Bruneck study. Stroke 2003;34:610–15. doi:10.1161/01.STR.0000058481.82639.EF
      OpenUrlAbstract/FREE Full Text
    32. ↵
      1. Chen Y,
      2. Segers S,
      3. Blaser MJ
      . Association between Helicobacter pylori and mortality in the NHANES III study. Gut 2013;62:1262–9. doi:10.1136/gutjnl-2012-303018
      OpenUrlAbstract/FREE Full Text
    33. ↵
      1. Ikeda A,
      2. Iso H,
      3. Sasazuki S, et al
      . The combination of Helicobacter pylori- and cytotoxin-associated gene-A seropositivity in relation to the risk of myocardial infarction in middle-aged Japanese: The Japan Public Health Center-based study. Atherosclerosis 2013;230:67–72. doi:10.1016/j.atherosclerosis.2013.06.013
      OpenUrlCrossRefPubMed
    34. ↵
      1. Schottker B,
      2. Adamu MA,
      3. Weck MN, et al
      . Helicobacter pylori infection, chronic atrophic gastritis and major cardiovascular events: a population-based cohort study. Atherosclerosis 2012;220:569–74. doi:10.1016/j.atherosclerosis.2011.11.029
      OpenUrlCrossRefPubMedWeb of Science
    View Abstract

    Supplementary materials

    • Supplementary Data

      This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

    Footnotes

    • Contributors MAS: designed experiments, data analysis, wrote first draft. Y-WRC: performed ELISAs for H. pylori. ST: assisted with assays. DT, RAW, JEC and SFPM: participated in interpretation of data, procurement of samples and data. DDS: participated in the design and execution of the experiments. All contributed to the write-up of the manuscript and approved the final paper.

    • Funding The study was funded by the Canadian Respiratory Research Network (CRRN), which was funded by the Canadian Institutes of Health Research (Institute of Circulatory and Respiratory Health Emerging Network); the Canadian Lung Association, the Canadian Thoracic Society and the Canadian Respiratory Health Professionals; the British Columbia Lung Association; with industry partner funding from AstraZeneca, Boehringer-Ingelheim (Canada), GlaxoSmithKline and Novartis Pharmaceuticals Canada.

    • Competing interests None declared.

    • Ethics approval UBC/PHCRI Institutional Review Board.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement The data are available from DDS.

    Linked Articles