Iron, haemochromatosis genotypes, and risk of infections: a cohort study of 142,188 general population individuals

It is unclear whether risk of infection is increased in individuals with hereditary haemochromatosis and in individuals with low or high plasma iron, transferrin saturation, or ferritin. Therefore, we tested whether high and low iron, transferrin saturation, and ferritin are associated with risk of infections observationally and genetically through HFE genotypes. We studied 142,188 Danish general population individuals. Iron, transferrin saturation, and ferritin were measured in 136,656, 136,599, and 38,020 individuals, respectively. HFE was genotyped for C282Y and H63D in 132,542 individuals. Median follow-up after study enrolment was 8 years(range:0-38years) for hospital and emergency room admissions with infections(n=20,394 individuals) using the National Patient Register, covering all Danish hospitals. Hazard ratios for any infection were 1.20(95%CI:1.12-1.28) and 1.14(1.07-1.22) in individuals with plasma iron≤5th or ≥95th percentile compared to individuals with iron from 26th-74th percentiles. Findings for transferrin saturation were similar, while infection risk was not increased in individuals with ferritin≤5th or ≥95th percentile. Hazard ratios in C282Y homozygotes versus non-carriers were 1.40(1.16-1.68) for any infection, 1.69(1.05-2.73) for sepsis, and 2.34(1.41-3.90) for death from infectious disease. Risk of infection was increased in C282Y homozygotes with normal plasma iron, transferrin saturation, or ferritin, and in C282Y homozygotes without liver disease, diabetes, and/or heart failure. In summary, low and high plasma iron and transferrin saturation were independently associated with increased infection risk. C282Y homozygotes had increased risk of any infection, sepsis, and death from infections. Even C282Y homozygotes with normal iron, transferrin saturation, or ferritin, not currently recommended for genotyping, had increased infection risk.

A Novel β-Globin Variant, Hb Raklev [β 75(E19) HBB:c.227T > A (Leu→Gln)]

We present a new hemoglobin variant, Hb Raklev, characterized by the substitution of leucine with glutamine at position 75 in the β-globin chain. This variant was discovered inadvertently during an HbA1c evaluation using high performance liquid chromatography in a symptomless 54-year-old Caucasian woman, with the same variant also identified in her 16-year-old daughter. Purification of the hemoglobin revealed possibly diminished 2,3-bisphosphoglycerate (2,3-BPG) sensitivity, which may result in heightened oxygen affinity. Notably, two variants have been previously documented at this location: the unstable Hb Atlanta and the high-affinity Hb Pasadena.

Acquired Spherocytosis in the Setting of Myelodysplasia

Hereditary spherocytosis (HS) is the most prevalent red blood cell (RBC) membrane disorder. We report a rare case of acquired SPTB spherocytosis coinciding with a myelodysplastic syndrome associated U2AF1 mutation, neither found in germline DNA. The diagnosis was confirmed by Eosin-5-Maleimide binding assay and Next Generation Sequencing (NGS). The patient recovered quickly after splenectomy, which confirms that his myelodysplastic syndrome (MDS)-associated U2AF1 mutation did not affect the clinical picture. This case highlights the essence of thoroughly examining the etiology of hemolytic indices, despite bone marrow morphology and myeloid gene panel supporting a diagnosis of MDS with single line dysplasia.

Genetic predisposition to long telomeres is associated with increased mortality after melanoma: A study of 2101 melanoma patients from hospital clinics and the general population

Whether there is an association between measured and genetically predicted telomere length and melanoma mortality is unclear. We tested the hypothesis that measured and genetically predicted telomere length is associated with mortality after a melanoma diagnosis. We followed 2,101 patients with melanoma from hospital clinics and the general population for risk of death for up to 26 years. All had telomere length measured in DNA from leukocytes, and 2052 of these were genotyped for the three single nucleotide polymorphisms rs7726159 (TERT), rs1317082 (TERC), and rs2487999 (OBFC1); all three genotypes are associated with telomere length and combined into an allele count from 0 to 6. For each telomere-lengthening allele, the hazard ratios (HRs) for mortality in the age-adjusted and multivariable-adjusted Cox analysis were 1.12 (95% confidence interval: 1.02-1.23) and 1.11 (1.01-1.23). However, for each standard deviation increase in measured telomere length, HR for mortality was 0.97 (0.88-1.08). In conclusion, in more than 2000 melanoma patients from hospital clinics and from the general population, genetically predicted long telomeres were associated with increased mortality, but measured leukocyte telomere length was not.

Investigation of Leukocyte Telomere Length and Genetic Variants in Chromosome 5p15.33 as Prognostic Markers in Lung Cancer

BACKGROUND

Lung cancer remains the leading cause of cancer mortality with relatively few prognostic biomarkers. We investigated associations with overall survival for telomere length (TL) and genetic variation in chromosome 5p15.33, an established telomere maintenance locus.

METHODS

Leukocyte TL was measured after diagnosis in 807 patients with non-small cell lung cancer (NSCLC) from the Princess Margaret Cancer Center in Toronto and assessed prospectively in 767 NSCLC cases from the Copenhagen City Heart Study and the Copenhagen General Population Study. Associations with all-cause mortality were tested for 723 variants in 5p15.33, genotyped in 4,672 NSCLC cases.

RESULTS

Short telomeres (≤10th percentile) were associated with poor prognosis for adenocarcinoma in both populations: TL measured 6 months after diagnosis [HR = 1.65; 95% confidence intervals (CI), 1.04-2.64] and for those diagnosed within 5 years after blood sampling (HR = 2.42; 95% CI, 1.37-4.28). Short TL was associated with mortality in never smokers with NSCLC (HR = 10.29; 95% CI, 1.86-56.86) and adenocarcinoma (HR = 11.31; 95% CI, 1.96-65.24). Analyses in 5p15.33 identified statistically significant prognostic associations for rs56266421-G in LPCAT1 (HR = 1.86; 95% CI, 1.38-2.52; P = 4.5 × 10^-5) in stage I-IIIA NSCLC, and for the SLC6A3 gene with OS in females with NSCLC (P = 1.6 × 10^-3).

CONCLUSIONS

Our findings support the potential clinical utility of TL, particularly for adenocarcinoma patients, while associations in chromosome 5p15.33 warrant further exploration.

IMPACT

This is the largest lung cancer study of leukocyte TL and OS, and the first to examine the impact of the timing of TL measurement. Our findings suggest that extremely short telomeres are indicative of poor prognosis in NSCLC.

Incidental lymphopenia and mortality: a prospective cohort study

BACKGROUND

It is unknown if incidental lymphopenia detected in the general population is associated with higher all-cause and cause-specific mortality. We aimed to identify the associations between lymphopenia and all-cause and cause specific mortality.

METHODS

In a prospective cohort study, we examined and followed participants enrolled in the Copenhagen General Population Study between November 2003 and April 2015. In our analysis, we modelled risks using Cox proportional hazards regression for 3 groups: participants with a lymphocyte count below the 2.5th percentile; those with a lymphocyte count at or between the 2.5th and 97.5th percentiles (reference category); and those with a lymphocyte count above the 97.5th percentile.

RESULTS

The cohort included 108 135 participants with a median age of 68 years. During a median follow-up of 9 (interquartile range [IQR] 0-14) years, 10 372 participants died. We found that participants with lymphopenia (lymphocyte count < 1.1 × 10⁹/L) compared with those with a lymphocyte count in the reference range (1.1-3.7 × 10⁹/L) had higher mortality with multivariable adjusted hazard ratios (HRs) of 1.63 (95% confidence interval [CI] 1.51-1.76) for all causes, 1.67 (95% CI 1.42-1.97) for nonhematologic cancers, 2.79 (95% CI 1.82-4.28) for hematologic cancers, 1.88 (95% CI 1.61-2.20) for cardiovascular diseases, 1.88 (95% CI 1.55-2.29) for respiratory diseases, 1.86 (95% CI 1.53-2.25) for infectious diseases, and 1.50 (95% CI 1.19-1.88) for other causes. For all-cause mortality, the highest absolute 2-year risks of death were observed in women (61%) and men (75%) who smoked and were aged 80 years or older with lymphocyte counts less than 0.5 × 10⁹/L. Participants with a lymphocyte count higher than the reference category had increased mortality (adjusted HR 1.17, 95% CI 1.04-1.31).

INTERPRETATION

We found that lymphopenia was associated with an increased risk of all-cause and cause-specific mortality.

Elevated plasma YKL-40 and risk of infectious disease: a prospective study of 94665 individuals from the general population

OBJECTIVES

YKL-40 is an acute phase protein elevated in patients with infectious and inflammatory diseases. We tested the hypothesis that baseline elevated YKL-40 is associated with increased risk of future infectious disease in healthy individuals in the general population.

METHODS

We prospectively followed 94 665 individuals from the Danish general population for up to 23 years and analysed for plasma YKL-40 levels (n = 21 584) and CHI3L1 rs4950928 genotype (n = 94 184). Endpoints were any infection, bacterial pneumonia, urinary tract infection, skin infection, sepsis, diarrhoeal disease, and other infections.

RESULTS

For YKL-40 percentile category 91-100% versus 0-33%, the multifactorially and C-reactive protein (CRP) adjusted hazard ratios were 1.71 (95% confidence interval 1.50-1.96; p 4 × 10^-14) for any infection, 1.97 (1.64-2.37; p 4 × 10^-13) for bacterial pneumonia, 1.62 (1.24-2.11; p 0.002) for urinary tract infection, 1.74 (1.31-2.32; p 2 × 10^-4) for skin infection, 1.76 (1.25-2.46; p 0.004) for sepsis, 1.90 (1.29-2.78; p 0.002) for diarrhoeal disease and 2.71 (1.38-5.35; p 0.01) for other infections. In multifactorially and CRP-adjusted models, a twofold increase in YKL-40 was associated with increased risk of all infectious disease endpoints. Mendelian randomization did not support causality, as CHI3L1 rs4950928 was associated with 94% and 190% higher YKL-40 levels (for CG and CC versus GG genotype), but not with increased risk of any infectious disease endpoint.

DISCUSSION

Baseline elevated plasma YKL-40 was not a cause but a strong marker of increased risk of future infectious diseases in individuals in the general population.

Arterial and venous thrombosis by high platelet count and high hematocrit: 108 521 individuals from the Copenhagen General Population Study

BACKGROUND

It is unclear whether high platelet count or high hematocrit predict risk of thrombosis in individuals from the general population.

OBJECTIVES

We tested the hypothesis that individuals from the general population with high platelet count or high hematocrit have high risk of arterial and venous thrombosis.

METHODS

We prospectively followed 108 521 individuals from The Copenhagen General Population Study for a median of 8 years. Platelet count and blood hematocrit were measured at study entry.

RESULTS AND CONCLUSION

Multivariable adjusted hazard ratios for individuals with platelet counts in the top 5 percentiles (>398 × 109 /L) vs in the 25th-75th percentiles (231-316 × 109 /L) were 1.77 (95% confidence interval [CI], 1.38-2.24) for arterial thrombosis in the brain (38 and 26 events/10 000 person-years) and 0.82 (95%, 0.61-1.11) for arterial thrombosis in the heart (23 and 28 events/10 000 person-years). For individuals with hematocrit values in the top 5 percentiles (women/men: >45/>48%) vs the 25th-75th percentiles (women/men: 38.1-42/41.1-45%), hazard ratios were 1.27 (95% CI, 0.91-1.75) for arterial thrombosis in the brain (40 and 26 events/10 000 person-years) and 1.46 (95% CI, 1.06-2.00) for arterial thrombosis in the heart (43 and 25 events/10 000 person-years). Neither high platelet count nor high hematocrit was associated with risk of venous thromboembolism. When excluding individuals with myeloproliferative neoplasia from the main analyses, results on risk of thrombosis were similar. In this prospective study, high platelet counts were associated with 1.8-fold risk of arterial thrombosis in the brain, whereas high hematocrit was associated with 1.5-fold risk of arterial thrombosis in the heart.

Measured and genetically predicted plasma YKL-40 levels and melanoma mortality

PURPOSE

High plasma levels of YKL-40 might be associated with mortality in patients with melanoma, and it is unknown if YKL-40 is causally related to mortality.

EXPERIMENTAL DESIGN

We studied two cohorts: 2618 patients with melanoma from hospital clinics and 1413 general population patients with melanoma, totalling 4031 patients followed up for mortality end-points for up to 20 years. All were genotyped for CHI3L1 rs4950928, highly predictive of lifelong plasma YKL-40, and plasma YKL-40 levels were measured in 2165 patients. We tested the hypotheses that measured and genetically predicted high plasma YKL-40 are associated with increased mortality in patients with melanoma.

RESULTS

For the hospital melanoma cohort, age- and sex-adjusted hazard ratios for death in individuals with measured plasma YKL-40 in the 96-100th percentile versus 1-95th percentile and per 10-percentile increase were 1.52 (95% confidence interval, 1.07-2.16) and 1.07 (1.02-1.11), respectively, most pronounced for patients with localised melanomas. Each C-allele of the CHI3L1 rs4950928 genotype was associated with plasma YKL-40 level increases of 32% in the hospital melanoma cohort (p = 6 × 10^-48) and 43% in the general population melanoma cohort (p = 7 × 10^-13). Multifactorially adjusted ratios for these increases in the combined cohorts were 1.04 (1.00-1.09) observationally for measured plasma YKL-40 and 0.98 (0.86-1.12) for the genetically predicted plasma YKL-40.

CONCLUSION

Measured, but not genetically predicted, increasing plasma YKL-40 was associated with increased mortality in patients with melanoma. Plasma YKL-40 is a marker but less likely to be a cause of increased mortality in patients with melanoma.

Bone marrow mononuclear cell telomere length in acute myeloid leukaemia and high-risk myelodysplastic syndrome

OBJECTIVE

Short telomere length is a known risk factor for developing clonal haematopoietic stem cell disorders, probably due to chromosomal instability. We tested the hypotheses that bone marrow mononuclear cell telomere length change from diagnosis through chemotherapy-induced remission and relapse, and that long telomere length is associated with low risk of relapse and all-cause mortality in patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome.

METHODS

We measured telomere length in bone marrow mononuclear cells from 233 patients at diagnosis, 112 patients at chemotherapy-induced remission and 58 patients at relapse of disease.

RESULTS

In patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome, bone marrow mononuclear cell telomere length was similar at diagnosis and relapse, but increased after chemotherapy-induced remission. Furthermore, bone marrow mononuclear cell telomere length was longer in patients with higher age at diagnosis. There was no association between telomere length at diagnosis, remission or relapse and all-cause mortality, nor did we find any association between telomere length at diagnosis or remission and risk of relapse.

CONCLUSION

In patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome, bone marrow mononuclear cell telomere length increased from diagnosis to remission. Furthermore, telomere length paradoxically was longer at higher age at diagnosis, even after adjusting for known risk factors of disease severity. Finally, we did not detect any prognostic information in telomere length.

Lymphopenia and risk of infection and infection-related death in 98,344 individuals from a prospective Danish population-based study

BACKGROUND

Neutropenia increases the risk of infection, but it is unknown if this also applies to lymphopenia. We therefore tested the hypotheses that lymphopenia is associated with increased risk of infection and infection-related death in the general population.

METHODS AND FINDINGS

Of the invited 220,424 individuals, 99,191 attended examination. We analyzed 98,344 individuals from the Copenhagen General Population Study (Denmark), examined from November 25, 2003, to July 9, 2013, and with available blood lymphocyte count at date of examination. During a median of 6 years of follow-up, they developed 8,401 infections and experienced 1,045 infection-related deaths. Due to the completeness of the Danish civil and health registries, none of the 98,344 individuals were lost to follow-up, and those emigrating (n = 385) or dying (n = 5,636) had their follow-up truncated at the day of emigration or death. At date of examination, mean age was 58 years, and 44,181 (44.9%) were men. Individuals with lymphopenia (lymphocyte count < 1.1 × 109/l, n = 2,352) compared to those with lymphocytes in the reference range (1.1-3.7 × 109/l, n = 93,538) had multivariable-adjusted hazard ratios of 1.41 (95% CI 1.28-1.56) for any infection, 1.31 (1.14-1.52) for pneumonia, 1.44 (1.15-1.79) for skin infection, 1.26 (1.02-1.56) for urinary tract infection, 1.51 (1.21-1.89) for sepsis, 1.38 (1.01-1.88) for diarrheal disease, 2.15 (1.16-3.98) for endocarditis, and 2.26 (1.21-4.24) for other infections. The corresponding hazard ratio for infection-related death was 1.70 (95% CI 1.37-2.10). Analyses were adjusted for age, sex, smoking status, cumulative smoking, alcohol intake, body mass index, plasma C-reactive protein, blood neutrophil count, recent infection, Charlson comorbidity index, autoimmune diseases, medication use, and immunodeficiency/hematologic disease. The findings were robust in all stratified analyses and also when including only events later than 2 years after first examination. However, due to the observational design, the study cannot address questions of causality, and our analyses might theoretically have been affected by residual confounding and reverse causation. In principle, fluctuating lymphocyte counts over time might also have influenced analyses, but lymphocyte counts in 5,181 individuals measured 10 years after first examination showed a regression dilution ratio of 0.68.

CONCLUSIONS

Lymphopenia was associated with increased risk of hospitalization with infection and increased risk of infection-related death in the general population. Notably, causality cannot be deduced from our data.

Mononuclear Cell Telomere Attrition Is Associated with Overall Survival after Nonmyeloablative Allogeneic Hematopoietic Cell Transplantation for Hematologic Malignancies

After allogeneic hematopoietic cell transplantation (allo-HCT), transplanted cells rapidly undergo multiple rounds of division. This may cause extensive telomere attrition, which could potentially prohibit further cell division and lead to increased mortality. We therefore characterized the development in telomere length after nonmyeloablative allo-HCT in 240 consecutive patients transplanted because of hematologic malignancies and tested the hypothesis that extensive telomere attrition post-transplant is associated with low overall survival. Telomere length was measured using quantitative PCR in mononuclear cells obtained from donors and recipients pretransplant and in follow-up samples from recipients post-transplant. Telomere attrition at 9 to 15 months post-transplant was calculated as the difference between recipient telomere length at 9 to 15 months post-transplant and donor pretransplant telomere length, divided by donor pretransplant telomere length. Although allo-HCT led to shorter mean telomere length in recipients when compared with donors, recipients had longer mean telomere length 9 to 15 months post-transplant than they had pretransplant. When compared with donor telomeres, recipients with extensive telomere attrition at 9 to 15 months post-transplant had low overall survival (10-year survival from 9 to 15 months post-transplant and onward: 68% in the tertile with least telomere attrition, 57% in the middle tertile, and 39% in the tertile with most attrition; log-rank P = .01). Similarly, after adjusting for potential confounders, recipients with extensive telomere attrition had high all-cause mortality (multivariable adjusted hazard ratio, 1.84 per standard deviation of telomere attrition at 9 to 15 months post-transplant; 95% confidence interval, 1.25 to 2.72; P = .002) and high relapse-related mortality (subhazard ratio, 2.07; 95% confidence interval, 1.14 to 3.76; P = .02). Taken together, telomere attrition may be a clinically relevant marker for identifying patients at high risk of mortality.

Asthma, other atopic conditions and risk of infections in 105 519 general population never and ever smokers

BACKGROUND

Individuals with atopic conditions may have increased susceptibility to infections outside the organs directly affected by their atopic condition.

OBJECTIVE

We tested the hypothesis that atopic conditions overall, and stratified by smoking history, are associated with increased risk of hospitalization for infections.

METHODS

We collected information on smoking history and self-reported atopic conditions from 105 519 individuals from the general population and followed them for up to 23 years for infectious disease hospitalizations and deaths. For asthma, we focused on never smokers with asthma diagnosed before age 50 (early asthma) to minimize confounding by chronic obstructive pulmonary disease.

RESULTS

During follow-up, 11 160 individuals had infections. Never smokers with early asthma versus no atopic conditions had significantly increased risks of any infection (hazard ratio 1.65; 95% confidence interval 1.40-1.94), pneumonia (2.44; 1.92-3.11) and any non-respiratory tract infection (1.36; 1.11-1.67); results were similar in ever smokers. Never smokers with any asthma had significantly increased risks of any infection (1.44; 1.24-1.66) and pneumonia (1.99; 1.62-2.44). Neither atopic dermatitis (1.00; 0.91-1.10) nor hay fever (1.00; 0.93-1.07) was associated with risk of any infection. In never smokers, risk estimates for any infection were comparable between asthma and diabetes, as were the population attributable fractions of 2.2% for any asthma and 2.9% for diabetes.

CONCLUSION

Early asthma was associated with significantly increased risks of any infection, pneumonia and any non-respiratory tract infection in never and ever smokers. In never smokers, risk estimates as well as population attributable fractions for any infection were comparable between asthma and diabetes, suggesting that asthma may be a substantial risk factor for infections in the general population.

Shorter leukocyte telomere length is associated with higher risk of infections: a prospective study of 75,309 individuals from the general population

In the general population, older age is associated with short leukocyte telomere length and with high risk of infections. In a recent study of allogeneic hematopoietic cell transplantation for severe aplastic anemia, long donor leukocyte telomere length was associated with improved survival in the recipients. These findings suggest that leukocyte telomere length could possibly be a marker of immune competence. Therefore, we tested the hypothesis that shorter leukocyte telomere length is associated with higher risk of infectious disease hospitalization and infection-related death. Relative peripheral blood leukocyte telomere length was measured using quantitative polymerase chain reaction in 75,309 individuals from the general population and the individuals were followed for up to 23 years. During follow up, 9228 individuals were hospitalized with infections and infection-related death occurred in 1508 individuals. Shorter telomere length was associated with higher risk of any infection (hazard ratio 1.05 per standard deviation shorter leukocyte telomere length; 95% confidence interval 1.03–1.07) and pneumonia (1.07; 1.03–1.10) after adjustment for conventional infectious disease risk factors. Corresponding hazard ratios for infection-related death were 1.10 (1.04–1.16) for any infection and 1.11 (1.04–1.19) for pneumonia. Telomere length was not associated with risk of skin infection, urinary tract infection, sepsis, diarrheal disease, endocarditis, meningitis or other infections. In conclusion, our findings indicate that leukocyte telomere length may be a marker of immune competence. Further studies are needed to determine whether risk of infections in allogeneic hematopoietic cell transplantation recipients can be reduced by considering donor leukocyte telomere length when selecting donors.

Smoking Cessation and the Microbiome in Induced Sputum Samples from Cigarette Smoking Asthma Patients

Asthma is a common disease causing cough, wheezing and shortness of breath. It has been shown that the lung microbiota in asthma patients is different from the lung microbiota in healthy controls suggesting that a connection between asthma and the lung microbiome exists. Individuals with asthma who are also tobacco smokers experience more severe asthma symptoms and smoking cessation is associated with improved asthma control. In the present study we investigated if smoking cessation in asthma patients is associated with a change in the bacterial community in the lungs, examined using induced sputum. We found that while tobacco smokers with asthma have a greater bacterial diversity in the induced sputum compared to non-smoking healthy controls, smoking cessation does not lead to a change in the microbial diversity.

IgE and risk of cancer in 37 747 individuals from the general population

BACKGROUND

Immunoglobulin E (IgE) is produced by plasma cells, often as part of an allergic immune response. It is currently unknown whether plasma IgE levels are associated with risk of cancer in individuals from the general population. We tested the hypothesis that high levels of plasma total IgE are associated with overall risk of cancer and with risk of specific cancers.

MATERIALS AND METHODS

Plasma total IgE was measured in 37 747 individuals from the general population, and the participants were followed prospectively for up to 30 years. All statistical tests were two-sided.

RESULTS

During a mean follow-up of 7 years, a first cancer was diagnosed in 3454 participants. The multivariable adjusted hazard ratio for a 10-fold higher level of IgE was 1.05 [95% confidence interval (CI) 1.00-1.11; P = 0.04] for any cancer, 0.44 (0.30-0.64; P = 0.00002) for chronic lymphocytic leukemia (CLL), 0.53 (0.33-0.84; P = 0.007) for multiple myeloma, 1.54 (1.04-2.29; P = 0.03) for other non-Hodgkin lymphoma, 1.38 (1.04-1.84; P = 0.03) for cancer of the oral cavity and pharynx, and 1.12 (1.00-1.25; P = 0.05) for lung cancer. The findings for CLL and multiple myeloma were generally robust; however, after correcting for 27 multiple comparisons only the finding for CLL remained significant.

CONCLUSION

High levels of plasma total IgE were associated with low risk of CLL and possibly of multiple myeloma, without convincing evidence for high risk of any cancer type.

Predictors of neutrophilic airway inflammation in young smokers with asthma

INTRODUCTION

Asthma is one of the most widespread chronic diseases worldwide. In spite of numerous detrimental effects on asthma, smoking is common among asthma patients. These smoking-induced aggravations of asthma may be attributed to changes in airway inflammation, which is characterized by a higher degree of neutrophilic inflammation than in non-smokers. A state of neutrophilic inflammation may lead to increased steroid resistance and an accelerated loss of lung function owing to tissue destruction. The aim of this study was to elucidate predictors of neutrophilic inflammation in young asthmatic smokers not on steroid treatment, including analysis of tobacco history and bacterial colonization.

METHODS

In a cross-sectional study, 52 steroid-free, current smokers with asthma were examined with induced sputum, fractional exhaled nitric oxide (FeNO), lung function, ACQ6 score, mannitol and methacholine challenge. A sample from the sputum induction was taken for bacterial analysis using 16S gene PCR technique and sequencing.

RESULTS

Using one-way analysis of variance and binary and linear regression models, only age and ACQ6 score were found to be significant predictors for airway neutrophilia. The investigation also included analysis for effect of pack years, current tobacco consumption, body mass index, lung function, FeNO; methacholine and mannitol responsiveness, atopy, gender, asthma history and presence of bacteria. The most common potentially pathogenic bacteria found were Streptococcus spp., Haemophilus spp. and Mycoplasma spp.

CONCLUSION

In this study, no tobacco-related predictors of airway neutrophilia were found, indicating that in the younger years of asthma patients who smoke, the amount of tobacco smoked in life does not influence the degree of neutrophilia. Conversely, for asthmatic smokers, neutrophilia may be induced when a certain threshold of tobacco consumption is reached.