Loud noise exposure and acoustic neuroma.

The results from studies of loud noise exposure and acoustic neuroma are conflicting. A population-based case-control study of 451 acoustic neuroma patients and 710 age-, sex-, and region-matched controls was conducted in Sweden between 2002 and 2007. Occupational exposure was based on historical measurements of occupational noise (321 job titles summarized by a job exposure matrix) and compared with self-reported occupational noise exposure. We also evaluated self-reported noise exposure during leisure activity. Conditional logistic regression was used to estimate odds ratios. There was no statistically significant association between acoustic neuroma and persistent occupational noise exposure, either with or without hearing protection. Exposure to loud noise from leisure activity without hearing protection was more common among acoustic neuroma cases (odds ratio = 1.47, 95% confidence interval: 1.06, 2.03). Statistically significant odds ratios were found for specific leisure activities including attending concerts/clubs/sporting events (odds ratio = 1.82, 95% confidence interval: 1.09, 3.04) and participating in workouts accompanied by loud music (odds ratio = 2.84, 95% confidence interval: 1.37, 5.89). Our findings do not support an association between occupational exposure to loud noise and acoustic neuroma. Although we report statistically significant associations between leisure-time exposures to loud noise without hearing protection and acoustic neuroma, especially among women, we cannot rule out recall bias as an alternative explanation.

Comorbid conditions associated with glioblastoma.

To inform clinical management of glioblastoma patients, we estimated the relative prevalence (present at glioblastoma diagnosis) and incidence (newly diagnosed) of comorbid conditions among these patients and their matched controls. We identified 2,424 glioblastoma patients registered in the Swedish National Cancer Registry between 1993 and 2006. Next, 12,120 randomly sampled population-based controls were individually matched to cases on age, sex and calendar year of diagnosis. We then evaluated patient discharge data for selected potential comorbid conditions. Seizures (odds ratio (OR) 31.6, 95% confidence interval (CI) 24.7-40.3) and cerebral edema (OR 25.0, 95% CI 5.5-114) were the most prevalent conditions at diagnosis. Beginning 30 days after diagnosis, increased risks of incident deep vein thrombosis (hazard ratio (HR) 119.7, 95% CI 60.8-211.0) and pulmonary embolism (HR 92.4, 95% CI 48.3-176.6) were observed. Risks of incident cardiovascular diseases including heart failure (HR 4.0, 95% CI 2.6-6.1), coronary artery disease (HR 2.3, 95% CI 1.7-3.2), and myocardial infarction (HR 1.9, 95% CI 1.1-3.4) were also elevated among glioblastoma patients. In this first population-based study of both prevalent and incident comorbid conditions among glioblastoma patients, we have quantified risk of those conditions related to the tumor and its treatment-based on nationwide registry data. However, for incident conditions we cannot distinguish between the effects of the tumor and the effects of treatment. A novel finding was the elevated risk of cardiovascular disease among glioblastoma patients; glioblastoma patients should be monitored for signs of cardiovascular disease.

Inherited variation in immune genes and pathways and glioblastoma risk.

To determine whether inherited variations in immune function single-nucleotide polymorphisms (SNPs), genes or pathways affect glioblastoma risk, we analyzed data from recent genome-wide association studies in conjunction with predefined immune function genes and pathways. Gene and pathway analyses were conducted on two independent data sets using 6629 SNPs in 911 genes on 17 immune pathways from 525 glioblastoma cases and 602 controls from the University of California, San Francisco (UCSF) and a subset of 6029 SNPs in 893 genes from 531 cases and 1782 controls from MD Anderson (MDA). To further assess consistency of SNP-level associations, we also compared data from the UK (266 cases and 2482 controls) and the Mayo Clinic (114 cases and 111 controls). Although three correlated epidermal growth factor receptor (EGFR) SNPs were consistently associated with glioblastoma in all four data sets (Mantel-Haenzel P values = 1 × 10⁻5 to 4 × 10⁻³), independent replication is required as genome-wide significance was not attained. In gene-level analyses, eight immune function genes were significantly (minP < 0.05) associated with glioblastoma; the IL-2RA (CD25) cytokine gene had the smallest minP values in both UCSF (minP = 0.01) and MDA (minP = 0.001) data sets. The IL-2RA receptor is found on the surface of regulatory T cells potentially contributing to immunosuppression characteristic of the glioblastoma microenvironment. In pathway correlation analyses, cytokine signaling and adhesion-extravasation-migration pathways showed similar associations with glioblastoma risk in both MDA and UCSF data sets. Our findings represent the first systematic description of immune genes and pathways that characterize glioblastoma risk.

Bacterial 16S sequence analysis of severe caries in young permanent teeth.

Previous studies have confirmed the association of the acid producers Streptococcus mutans and Lactobacillus spp. with childhood caries, but they also suggested these microorganisms are not sufficient to explain all cases of caries. In addition, health-associated bacterial community profiles are not well understood, including the importance of base production and acid catabolism in pH homeostasis. The bacterial community composition in health and in severe caries of the young permanent dentition was compared using Sanger sequencing of the ribosomal 16S rRNA genes. Lactobacillus species were dominant in severe caries, and levels rose significantly as caries progressed from initial to deep lesions. S. mutans was often observed at high levels in the early stages of caries but also in some healthy subjects and was not statistically significantly associated with caries progression in the overall model. Lactobacillus or S. mutans was found either at low levels or not present in several samples. Other potential acid producers observed at high levels in these subjects included strains of Selenomonas, Neisseria, and Streptococcus mitis. Propionibacterium FMA5 was significantly associated with caries progression but was not found at high levels. An overall loss of community diversity occurred as caries progressed, and species that significantly decreased included the Streptococcus mitis-S. pneumoniae-S. infantis group, Corynebacterium matruchotii, Streptococcus gordonii, Streptococcus cristatus, Capnocytophaga gingivalis, Eubacterium IR009, Campylobacter rectus, and Lachnospiraceae sp. C1. The relationship of acid-base metabolism to 16S rRNA gene-based species assignments appears to be complex, and metagenomic approaches that would allow functional profiling of entire genomes will be helpful in elucidating the microbial pathogenesis of caries.

Occupational exposures and risk of acoustic neuroma.

OBJECTIVES: Acoustic neuroma is a benign tumour accounting for approximately 6-10% of all intracranial tumours and occurs mainly in patients aged ≥50 years. Our aim was to investigate a wide range of occupational exposures, individual occupational titles and socioeconomic status (SES) as potential risk factors for acoustic neuroma. METHODS: We conducted a population-based case-control study of 793 acoustic neuroma cases identified through the Swedish Cancer Registry and 101,762 randomly selected controls. Information on SES and occupation was obtained from censuses and linked to job-exposure matrices. Logistic regression was used to estimate ORs and calculate 95% CIs. RESULTS: An increased OR was seen for mercury exposure <10 years before the reference year (OR 2.9; 95% CI 1.2 to 6.8), and a more modest association for benzene exposure (OR 1.8; 95% CI: 1.0 to 3.2) ≥10 years before the reference year. We observed a threefold increased risk for females working as tailors and dressmakers ≥10 years before the reference year, and a more than threefold significantly elevated OR for those working as truck and conveyor operators <10 years before the reference year. We found no convincing evidence that SES is related to disease development. CONCLUSION: We observed an increased risk of acoustic neuroma associated with occupational exposure to mercury, benzene and textile dust. Men working as truck and conveyor operators <10 years before the reference year had the highest increased risk of acoustic neuroma, but it is unclear what in those occupations might contribute to disease development. Our study also suggested an association between acoustic neuroma and being a class teacher or policeman. However, these findings should be further investigated to exclude the possibility of detection bias.

Occupational noise exposure and risk of acoustic neuroma.

A small number of prior epidemiologic studies of occupational noise exposure based on self-report have suggested an association with acoustic neuroma. The goal of the present study was to further examine the association between noise exposure and acoustic neuroma by using an objective measure of exposure in the form of a job exposure matrix. A total of 793 acoustic neuroma cases aged 21-84 years were identified between 1987 and 1999 from the Swedish Cancer Registry. The 101,756 controls randomly selected from the study base were frequency matched to cases on age, sex, and calendar year of diagnosis. Occupational information, available for 599 of the cases and 73,432 of the controls, was obtained from censuses and was linked to a job exposure matrix based on actual noise measurements. All risk estimates were close to unity, regardless of noise exposure level or parameter. The overall odds ratio for exposure to > or = 85 dB of noise was 0.89 (95% confidence interval: 0.64, 1.23). Contrary to previous study results, the present findings did not demonstrate an increased acoustic neuroma risk related to occupational noise exposure even after allowing for a long latency period. The effect of nondifferential misclassification of exposure must be considered a potential cause of the negative findings.

An international case-control study of glutathione transferase and functionally related polymorphisms and risk of primary adult brain tumors.

BACKGROUND: Glutathione transferases (GST) detoxify environmental and endogenous compounds and levels of two polymorphic GST proteins, GSTM3 and GSTP1, are high in the brain. Previous studies of GSTM3 and GSTP1 polymorphisms and adult brain tumor risk have produced inconsistent results, whereas the GSTM3 -63 variant is newly identified and, therefore, has not yet been studied in this context. We therefore examined associations between GSTM3 -63, GSTM3 *A/*B, GSTP1 105, and GSTP1 114 variants and adult brain tumor risk and the interaction of the effects of these same polymorphisms with cigarette smoking. In addition, the enzymes NQO1 and CYP1A1 alter susceptibility to oxidative brain damage. Because there is less previous evidence for a role of NQO1, CYP1A1, GSTM1, and GSTT1 variants, we restricted analysis of these variants to a small preliminary study. METHODS: We genotyped DNA collected for an international population-based case-control study of 725 glioma cases, 329 of which were glioblastoma cases, 546 meningioma cases and 1,612 controls. Study participants were residents of Sweden, southeast England, Denmark, and Finland. RESULTS: We found no associations between the GSTM3, GSTP1, NQO1, CYP1A1, GSTM1, or GSTT1 polymorphisms and adult brain tumor risk with the possible exception of a weak association between the G-C (Val-Ala) GSTP1 105/114 haplotype and glioma [odds ratio (OR), 0.73; 95% confidence interval (95% CI), 0.54, 0.99], nor was there an interaction between the effects of the GSTM3 or GSTP1 polymorphisms and cigarette smoking. CONCLUSIONS: Overall, we observed no strong evidence for an association between GST or related enzyme polymorphisms and adult brain tumor risk.

An international case-control study of interleukin-4Ralpha, interleukin-13, and cyclooxygenase-2 polymorphisms and glioblastoma risk.

Previous studies found that allergies are inversely related to risk of glioma. In an earlier publication, using data from a Swedish case-control study, Schwartzbaum et al. report an inverse relation between risk of glioblastoma and four single nucleotide polymorphisms (SNP) on two genes [interleukin (IL)-4Ralpha, IL-13] that are associated with allergies. In addition, recent studies suggest that IL-4 and IL-13 induce cyclooxygenase-2 (COX-2) to resolve brain inflammation. To see whether previous Swedish results (110 cases, 430 controls) would be replicated, we estimated the association between glioblastoma and two IL-4Ralpha (rs1805015, rs1801275) and two IL-13 (rs20541, rs1800925) SNPs and their haplotypes and one COX-2 SNP (-765GC) using additional English, Danish, and Finnish data (217 cases, 1,171 controls). Among general population controls, we evaluated associations between these haplotypes, the COX-2 SNP, and self-reported allergies. Our data did not support our original observations relating individual IL-4Ralpha, IL-13, or COX-2 SNPs to glioblastoma risk. However, the T-G IL-4Ralpha haplotype was associated with glioblastoma risk (odds ratio, 2.26; 95% confidence interval, 1.13-4.52) and there was a suggestion of an inverse relation between this haplotype and hayfever prevalence among controls (odds ratio, 0.38; 95% confidence interval, 0.14-1.03). The lack of support for a link between four IL-4Ralpha and IL-13 SNPs and glioblastoma may reflect the absence of associations or may result from uncontrolled confounding by haplotypes related both to those that we examined and glioblastoma. Nonetheless, the association between the T-G IL-4Ralpha haplotype and glioblastoma risk may indicate a role of immune factors in glioblastoma development.

Epidemiology of brain tumors.

Brain tumors seemed to have increased in incidence over the past 30 years, but the rise probably results from use of new neuroimaging techniques. Treatments have not improved prognosis for rapidly fatal brain tumors. Established brain tumor risk factors (exposure to ionizing radiation, rare mutations of penetrant genes, and familial history) explain only a small proportion of brain tumors, and only one of these potentially is modifiable. Genetic and environmental characteristics likely play a role in familial aggregation of glioma and these factors are not identified. New concepts in brain tumor etiology and clinical management are the goal of research, with an aim at eradicating this devastating disease.

Comorbidity among the morbidly obese: a comparative study of 2002 U.S. hospital patient discharges.

BACKGROUND: Increased morbidity is associated with increasing severity of obesity. However, among morbidly obese patients, comorbid prevalence has been reported primarily in the bariatric surgical literature. This study compares demographic characteristics and selected comorbid conditions of morbidly obese patients discharged after surgical obesity procedures and morbidly obese patients discharged after all other hospital procedures. METHODS: The 2002 National Hospital Discharge Survey (a nationally representative sample of hospital discharge records) and the International Classification of Diseases, 9th Revision, Clinical Modification were used to identify and describe all morbidly obese patient discharges (n = 3,473) and to quantify the prevalence of selected obesity-related comorbid conditions. RESULTS: Compared with all other morbidly obese patients, the obesity surgery patients (n = 833) were younger (median, 42 vs 48 years; range, 17 to 67) and more female (82.3% vs. 63.7%), with higher rates of sleep apnea (24.0% vs. 11.8%), osteoarthritis (22.9% vs. 11.8%), and gastroesophageal reflux disease (27.7% vs. 11.7%) (all P < .001). The prevalence of type 2 diabetes mellitus was lower in the obesity surgery patients (16.1% vs. 24.3%; P = .003), whereas the rates of hypertension (45.9% vs. 41.0%; P = .13) and asthma (9.6% vs. 12.0%; P = .26) were similar in the two groups. CONCLUSIONS: Demographic characteristics and comorbid prevalence of morbidly obese patients discharged after obesity surgery are consistent with reports in the bariatric surgical literature. Obesity surgery patients had a higher prevalence of some comorbid conditions. Possible explanations for this include preferential diagnosis, differential diagnostic coding, or increased severity of morbid obesity. Advancing surgical and insurance guidelines for bariatric surgery will require clinical data that accurately describe and quantify the demographic distribution of obesity and the associated burden of disease.

The molecular epidemiology of gliomas in adults.

In this paper the authors highlight recent findings from molecular epidemiology studies of glioma origin and prognosis and suggest promising paths for future research. The reasons for variation in glioma incidence according to time period of diagnosis, sex, age, ancestry and ethnicity, and geography are poorly understood, as are factors that affect prognosis. High-dose therapeutic ionizing irradiation and rare mutations in highly penetrant genes associated with certain rare syndromes--the only two established causes of glioma--can be called upon to explain few cases. Both familial aggregation of gliomas and the inverse association of allergies and immune-related conditions with gliomas have been shown consistently, but the explanations for these associations are inadequately developed or unknown. Several biomarkers do predict prognosis, but only evaluation of loss of 1p and 19q in oligodendroglial tumors are incorporated in clinical practice. Ongoing research focuses on classifying homogeneous groups of tumors on the basis of molecular markers and identifying inherited polymorphisms that may influence survival or risk. Because most cases of glioma have yet to furnish either an environmental or a genetic explanation, the greatest potential for discovery may lie in genomic studies in conjunction with continued evaluation of environmental and developmental factors. Large sample sizes and multidisciplinary teams with expertise in neuropathology, genetics, epidemiology, functional genomics, bioinformatics, biostatistics, immunology, and neurooncology are required for these studies to permit exploration of potentially relevant pathways and modifying effects of other genes or exposures, and to avoid false-positive findings. Improving survival rates for patients harboring astrocytic tumors will probably require many randomized clinical trials of novel treatment strategies.

Childhood brain tumor epidemiology: a brain tumor epidemiology consortium review.

Childhood brain tumors are the most common pediatric solid tumor and include several histologic subtypes. Although progress has been made in improving survival rates for some subtypes, understanding of risk factors for childhood brain tumors remains limited to a few genetic syndromes and ionizing radiation to the head and neck. In this report, we review descriptive and analytical epidemiology childhood brain tumor studies from the past decade and highlight priority areas for future epidemiology investigations and methodological work that is needed to advance our understanding of childhood brain tumor causes. Specifically, we summarize the results of a review of studies published since 2004 that have analyzed incidence and survival in different international regions and that have examined potential genetic, immune system, developmental and birth characteristics, and environmental risk factors. Cancer Epidemiol Biomarkers Prev; 23(12); 2716-36. ©2014 AACR.

The epidemiology of glioma in adults: a "state of the science" review.

Gliomas are the most common primary intracranial tumor, representing 81% of malignant brain tumors. Although relatively rare, they cause significant mortality and morbidity. Glioblastoma, the most common glioma histology (∼45% of all gliomas), has a 5-year relative survival of ∼5%. A small portion of these tumors are caused by Mendelian disorders, including neurofibromatosis, tuberous sclerosis, and Li-Fraumeni syndrome. Genomic analyses of glioma have also produced new evidence about risk and prognosis. Recently discovered biomarkers that indicate improved survival include O6-methylguanine-DNA methyltransferase methylation, isocitrate dehydrogenase mutation, and a glioma cytosine-phosphate-guanine island methylator phenotype. Genome-wide association studies have identified heritable risk alleles within 7 genes that are associated with increased risk of glioma. Many risk factors have been examined as potential contributors to glioma risk. Most significantly, these include an increase in risk by exposure to ionizing radiation and a decrease in risk by history of allergies or atopic disease(s). The potential influence of occupational exposures and cellular phones has also been examined, with inconclusive results. We provide a "state of the science" review of current research into causes and risk factors for gliomas in adults.

Risk factors for oligodendroglial tumors: a pooled international study.

Oligodendroglial tumors are rare subtypes of brain tumors and are often combined with other glial tumors in epidemiological analyses. However, different demographic associations and clinical characteristics suggest potentially different risk factors. The purpose of this study was to investigate possible risk factors for oligodendroglial tumors (including oligodendroglioma, anaplastic oligodendroglioma, and mixed glioma). Data from 7 case-control studies (5 US and 2 Scandinavian) were pooled. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for age group, gender, and study site. Data on 617 cases and 1260 controls were available for analyses. Using data from all 7 studies, history of allergies and/or asthma was associated with a decreased risk of anaplastic oligodendroglioma (OR = 0.6; 95% CI: 0.4-0.9), and history of asthma only was associated with a decreased risk of oligodendroglioma (OR = 0.5; 95% CI: 0.3-0.9) and anaplastic oligodendroglioma (OR = 0.3; 95% CI: 0.1-0.9). A family history of brain tumors was associated with an increased risk of anaplastic oligodendroglioma (OR = 2.2; 95% CI: 1.1-4.5). Having had chicken pox was associated with a decreased risk of oligodendroglioma (OR = 0.6; 95% CI: 0.4-0.9) and anaplastic oligodendroglioma (OR = 0.5; 95% CI: 0.3-0.9) in the US studies. Although there is some overlap in risk factors between oligodendroglial tumors and gliomas as a group, it is likely that additional factors specific to oligodendroglial tumors have yet to be identified. Large, multi-institution international studies will be necessary to better characterize these etiological risk factors.

Allergy and inflammatory transcriptome is predominantly negatively correlated with CD133 expression in glioblastoma.

Allergies and the use of anti-inflammatory medication appear to be associated with reduced glioblastoma risk. However, these observations may merely reflect systemic immunosuppression induced by the tumor. To better understand the effect of this tumor on allergies and inflammation, we used CD133 mRNA expression as an indicator of tumor aggressiveness and systematically examined its relation to mRNA expression levels of 919 allergy- and inflammation-related genes in 142 glioblastoma tissue samples. We found that 69% of these genes are negatively correlated with CD133 expression including allergy-related (eg, interleukin [IL]-4R-alpha; Pearson correlation coefficient [r] = - 0.40; 95% confidence interval [CI] = - 0.53, -0.25) and immunoregulatory genes (eg, TGF-beta1; r = - 0.35; 95% CI = - 0.49, -0.20). Exceptions to this negative trend include the proinflammatory cytokine IL-17-beta (r = 0.22; 95% CI = 0.06, 0.37) and 2 IL-17 receptors. Also positively related to CD133 expression are NCAM-1 (r = 0.45; 95% CI = 0.31, 0.57) and PDGFR-alpha (r = 0.45; 95% CI = 0.30, 0.57). Previous literature suggests that NCAM-1(+) T cells infiltrate glioblastoma and may cause suppression of antitumor immunity, whereas PDGFR-alpha is involved in neurogenesis and amplified in glioblastoma. Ours is the first study to document down-regulation of the majority of allergy- and inflammation-related genes with glioblastoma progression. However, IL-17 and NCAM-1 may play proinflammatory and immunosuppressive roles, respectively, during the late stage of glioblastoma progression. Our findings suggest that immune function continues to change as the tumor progresses.

Brain tumor epidemiology: consensus from the Brain Tumor Epidemiology Consortium.

Epidemiologists in the Brain Tumor Epidemiology Consortium (BTEC) have prioritized areas for further research. Although many risk factors have been examined over the past several decades, there are few consistent findings, possibly because of small sample sizes in individual studies and differences between studies in patients, tumor types, and methods of classification. Individual studies generally have lacked samples of sufficient size to examine interactions. A major priority based on available evidence and technologies includes expanding research in genetics and molecular epidemiology of brain tumors. BTEC has taken an active role in promoting understudied groups, such as pediatric brain tumors; the etiology of rare glioma subtypes, such as oligodendroglioma; and meningioma, which, although it is not uncommon, has only recently been registered systematically in the United States. There also is a pressing need for more researchers, especially junior investigators, to study brain tumor epidemiology. However, relatively poor funding for brain tumor research has made it difficult to encourage careers in this area. In this report, BTEC epidemiologists reviewed the group's consensus on the current state of scientific findings, and they present a consensus on research priorities to identify which important areas the science should move to address.

Exposure to loud noise and risk of acoustic neuroma.

Exposure to occupational loud noise has been previously identified as a possible risk factor for acoustic neuroma in only one relatively small (n = 86 cases) case-control study of men. The goal of the present study was to further examine the role of loud noise in acoustic neuroma etiology. In their population-based case-control study of both sexes conducted from 1999 to 2002 in Sweden, the authors compared reports on type and duration of occupational and nonoccupational loud noise exposure of 146 acoustic neuroma cases and 564 controls. Controls were randomly selected from the study base and were frequency matched on age, sex, and residential area. The authors found that individuals reporting loud noise exposure from any source were at increased risk for acoustic neuroma (odds ratio (OR) = 1.55, 95% confidence interval (CI): 1.04, 2.30). Exposure to loud noise from machines, power tools, and/or construction increased the risk for acoustic neuroma (OR = 1.79, 95% CI: 1.11, 2.89), as did exposure to loud music (OR = 2.25, 95% CI: 1.20, 4.23). The odds ratio for a latency period of 13 or more years since the first loud noise exposure from any source was 2.12 (95% CI: 1.40, 3.20). The findings of an increased risk of acoustic neuroma with loud noise exposure support previous research.