Improving sentiment analysis on clinical narratives by exploiting UMLS semantic types.

Sentiments associated with assessments and observations recorded in a clinical narrative can often indicate a patient's health status. To perform sentiment analysis on clinical narratives, domain-specific knowledge concerning meanings of medical terms is required. In this study, semantic types in the Unified Medical Language System (UMLS) are exploited to improve lexicon-based sentiment classification methods. For sentiment classification using SentiWordNet, the overall accuracy is improved from 0.582 to 0.710 by using logistic regression to determine appropriate polarity scores for UMLS 'Disorders' semantic types. For sentiment classification using a trained lexicon, when disorder terms in a training set are replaced with their semantic types, classification accuracies are improved on some data segments containing specific semantic types. To select an appropriate classification method for a given data segment, classifier combination is proposed. Using classifier combination, classification accuracies are improved on most data segments, with the overall accuracy of 0.882 being obtained.

Correction: Associations of sexually transmitted infections and bacterial vaginosis with abnormal cervical cytology: A cross-sectional survey with 9090 community women in China.

[This corrects the article DOI: 10.1371/journal.pone.0230712.].

Associations of sexually transmitted infections and bacterial vaginosis with abnormal cervical cytology: A cross-sectional survey with 9090 community women in China.

BACKGROUND: Although it is well acknowledged that persistent infection with high-risk human papillomavirus types in genital sites plays a crucial role in the development of squamous cell cervical carcinoma, there is no unanimous consensus on the association between non-HPV sexually transmitted infections and abnormal cervical cytology. METHODS: In the present study, we evaluated cervical cytology status, sexually transmitted infections and bacterial vaginosis status, and collected social-demographic information among recruited participants to explore the association of STIs and bacterial vaginosis with abnormal cervical cytology. RESULTS: 9,090 women's specimens were successfully tested, with a total of 8,733 (96.1%) women had normal cytology and 357 (3.9%) women exhibited abnormal cytology. The prevalence of HPV, Chlamydia trachomatis, Neisseria gonorrhoeae, and bacterial vaginosis was significantly higher in the ≥ASC-US group than the NILM group (P<0.05). Women with Neisseria gonorrhoeae infection (AOR = 5.30, 95% CIs = 1.30-21.51, P = 0.020) or bacterial vaginosis (AOR = 1.94, 95% CIs = 1.08-3.47, P = 0.026) exhibited an increased risk of abnormal cervical cytology after adjusted for carcinogenic HPV-positive status. CONCLUSIONS: Our results demonstrated that Neisseria gonorrhoeae infection in genital sites and/or bacterial vaginosis may independently increase the risk for cervical cytology abnormalities after adjusted for carcinogenic HPV-positive status. Besides, these results improved our understanding of the etiology of abnormal cervical cytology and may be useful for the management of women with ASC-US cytology.

Side-Chain Engineering of Donor-Acceptor Conjugated Small Molecules As Dopant-Free Hole-Transport Materials for Efficient Normal Planar Perovskite Solar Cells.

Simultaneously improving efficiency and stability, which are particularly crucial factors for the commercialization of perovskite solar cells (PSCs), remains a major challenge. For high-efficiency normal PSCs, the development of stable dopant-free hole-transport materials (HTMs) seems imperative. Here, we developed potential donor-acceptor small molecules (BTTI) as HTMs for normal planar PSCs. Through tailoring its alkyl side-chain length as BTTI-C6, BTTI-C8, and BTTI-C12, our results show that upon shortening the side chain of BTTI, the hole mobility, film-forming capability, and resultant device performance were remarkably improved, with the device conversion efficiencies of 19.69% for BTTI-C6, 18.89% for BTTI-C8, and 17.49% for BTTI-C12. Meanwhile, compared to those made with the routine doped Spiro-OMeTAD, devices based on our dopant-free HTMs exhibited significantly improved stability. This work paves the way to the development of effective dopant-free HTMs for high-performance PSCs.

A Narrow-Bandgap n-Type Polymer Semiconductor Enabling Efficient All-Polymer Solar Cells.

Currently, n-type acceptors in high-performance all-polymer solar cells (all-PSCs) are dominated by imide-functionalized polymers, which typically show medium bandgap. Herein, a novel narrow-bandgap polymer, poly(5,6-dicyano-2,1,3-benzothiadiazole-alt-indacenodithiophene) (DCNBT-IDT), based on dicyanobenzothiadiazole without an imide group is reported. The strong electron-withdrawing cyano functionality enables DCNBT-IDT with n-type character and, more importantly, alleviates the steric hindrance associated with typical imide groups. Compared to the benchmark poly(naphthalene diimide-alt-bithiophene) (N2200), DCNBT-IDT shows a narrower bandgap (1.43 eV) with a much higher absorption coefficient (6.15 × 104 cm-1 ). Such properties are elusive for polymer acceptors to date, eradicating the drawbacks inherited in N2200 and other high-performance polymer acceptors. When blended with a wide-bandgap polymer donor, the DCNBT-IDT-based all-PSCs achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm. Such efficiency greatly outperforms those of N2200 (6.13%) and the naphthalene diimide (NDI)-based analog NDI-IDT (2.19%). This work breaks the long-standing bottlenecks limiting materials innovation of n-type polymers, which paves a new avenue for developing polymer acceptors with improved optoelectronic properties and heralds a brighter future of all-PSCs.

Dopant-Free Small-Molecule Hole-Transporting Material for Inverted Perovskite Solar Cells with Efficiency Exceeding 21.

Hole-transporting materials (HTMs) play a critical role in realizing efficient and stable perovskite solar cells (PVSCs). Considering their capability of enabling PVSCs with good device reproducibility and long-term stability, high-performance dopant-free small-molecule HTMs (SM-HTMs) are greatly desired. However, such dopant-free SM-HTMs are highly elusive, limiting the current record efficiencies of inverted PVSCs to around 19%. Here, two novel donor-acceptor-type SM-HTMs (MPA-BTI and MPA-BTTI) are devised, which synergistically integrate several design principles for high-performance HTMs, and exhibit comparable optoelectronic properties but distinct molecular configuration and film properties. Consequently, the dopant-free MPA-BTTI-based inverted PVSCs achieve a remarkable efficiency of 21.17% with negligible hysteresis and superior thermal stability and long-term stability under illumination, which breaks the long-time standing bottleneck in the development of dopant-free SM-HTMs for highly efficient inverted PVSCs. Such a breakthrough is attributed to the well-aligned energy levels, appropriate hole mobility, and most importantly, the excellent film morphology of the MPA-BTTI. The results underscore the effectiveness of the design tactics, providing a new avenue for developing high-performance dopant-free SM-HTMs in PVSCs.

Causality Assessment of Adverse Drug Reaction: Controlling Confounding Induced by Polypharmacy.

BACKGROUND: Post-marketing pharmaceutical surveillance, a.k.a. pragmatic clinical trials (i.e., PCT), plays a vital role in preventing accidents in practical treatment. The most important and difficult task in PCT is to assess which drug causes adverse reactions (i.e., ADRs) from clinical texts. The confounding (i.e., factors cause confusions in causality assessment) is generated by the polypharmacy (i.e., multiple drugs use), which makes most of existing methods poor for detecting drugs that capably cause observed ADRs. OBJECTIVE: We aim to improve the performance of detecting drug-ADR causal relations from clinical texts. To this end, a mechanism for reducing the impact of confounding on the detecting process is needful. METHODS: We proposed a novel model which is called the analogy-based active voting (i.e., AAV) for improving the ability of detecting causal drug-ADR pairs, in case multiple drugs are prescribed for treating the comorbidity. This model is inspired by the analogy principle which was proposed by Bradford Hill. RESULTS: The experimental results show the improvement of recognizing causal relations between drugs and ADRs that are confirmed by the SIDER. In addition, the proposed model is promising to detect infrequently observed causal drug-ADR pairs when the drug is not commonly used. CONCLUSION: The proposed model demonstrates its ability for controlling the polypharmacy-induced confounding, to improve the quality of causality assessment of ADRs. Additionally, this also shows that the analogy principle is applicable for the assessment.

Understanding the Impact of Cu-In-Ga-S Nanoparticles Compactness on Holes Transfer of Perovskite Solar Cells.

Although a compact holes-transport-layer (HTL) film has always been deemed mandatory for perovskite solar cells (PSCs), the impact their compactness on the device performance has rarely been studied in detail. In this work, based on a device structure of FTO/CIGS/perovskite/PCBM/ZrAcac/Ag, that effect was systematically investigated with respect to device performance along with photo-physics characterization tools. Depending on spin-coating speed, the grain size and coverage ratio of those CIGS films on FTO substrates can be tuned, and this can result in different hole transfer efficiencies at the anode interface. At a speed of 4000 r.p.m., the band level offset between the perovskite and CIGS modified FTO was reduced to a minimum of 0.02 eV, leading to the best device performance, with conversion efficiency of 15.16% and open-circuit voltage of 1.04 V, along with the suppression of hysteresis. We believe that the balance of grain size and coverage ratio of CIGS interlayers can be tuned to an optimal point in the competition between carrier transport and recombination at the interface based on the proposed mechanism. This paper definitely deepens our understanding of the hole transfer mechanism at the interface of PSC devices, and facilitates future design of high-performance devices.

Novel Molecular Doping Mechanism for n-Doping of SnO2 via Triphenylphosphine Oxide and Its Effect on Perovskite Solar Cells.

Molecular doping of inorganic semiconductors is a rising topic in the field of organic/inorganic hybrid electronics. However, it is difficult to find dopant molecules which simultaneously exhibit strong reducibility and stability in ambient atmosphere, which are needed for n-type doping of oxide semiconductors. Herein, successful n-type doping of SnO2 is demonstrated by a simple, air-robust, and cost-effective triphenylphosphine oxide molecule. Strikingly, it is discovered that electrons are transferred from the R3P+ O- σ-bond to the peripheral tin atoms other than the directly interacted ones at the surface. That means those electrons are delocalized. The course is verified by multi-photophysical characterizations. This doping effect accounts for the enhancement of conductivity and the decline of work function of SnO2 , which enlarges the built-in field from 0.01 to 0.07 eV and decreases the energy barrier from 0.55 to 0.39 eV at the SnO2 /perovskite interface enabling an increase in the conversion efficiency of perovskite solar cells from 19.01% to 20.69%.

Extraction of Temporal Information from Clinical Narratives.

The existence of massive quantity of clinical text in electronic medical records (EMRs) has created significant demand for clinical text processing and information extraction in the field of health care and medical research. Detailed clinical observations of patients are typically recorded chronologically. Temporal information in such clinical texts consist of three elements: temporal expressions, temporal events, and temporal relations. Due to the implicit expression of temporal information, lack of writing quality, and domain-specific nature in the clinical text, extraction of temporal information is much more complex than for newswire texts. In spite of these difficulties, to extract temporal information using the annotated corpora, few research works reported rule-based, machine-learning, and hybrid methods. On the other hand, creating the annotated corpora is expensive, time-consuming, and demands significant human effort; the processing quality is inevitably affected by the small size of corpora. Motivated by this issue, in this research work, we present a novel method to effectively extract the temporal information from EMR clinical texts. The essential idea of this method is first to build a feature set appropriately for clinical expressions, followed by the development of a semi-supervised framework for temporal event extraction, and finally detection of temporal relations among events with a newly formulated hypothesis. Comparative experimental evaluation on the I2B2 data set has clearly shown improved performance of the proposed methods. Specifically, temporal event and relation extraction is possible with an F-measure 89.98 and 67.1% respectively.

[Association of single nucleotide polymorphisms of transcription factors with congenital heart diseases in the Chinese population: a Meta analysis].

OBJECTIVE: To study the association of single nucleotide polymorphisms (SNPs) of transcription factors (NKX2.5, GATA4, TBX5, and FOG2) with congenital heart disease (CHD) in the Chinese population. METHODS: PubMed, Google Scholar, CNKI, Wanfang Data, and Weipu Data were searched for articles on the association of SNPs of target genes with CHD in the Chinese population. If one locus was mentioned in at least two articles, the random or fixed effect model was used to perform a pooled analysis of study results and to calculate the pooled OR and its 95%CI. If a locus was mentioned in only one article, related data were extracted from this article to analyze the association between the SNPs of this locus and CHD. RESULTS: Twenty-three articles were included. The Meta analysis showed that there were significant differences between the CHD and control groups in the genotype and allele frequencies of GATA4 rs1139244 and rs867858 and the genotype frequency of GATA4 rs904018, while there were no significant differences in the SNPs of the other genetic loci between the two groups. The single-article analysis showed that there were significant differences between the two groups in the allele frequencies of NKX2.5 rs118026695/rs703752, GATA4 rs884662/rs12825/rs12458/rs3203358/rs4841588, and TBX5 rs6489956. There were no significant differences in the SNPs of FOG2 locus between the two groups. CONCLUSIONS: The SNPs of some loci in NKX2.5, GATA4, and TBX5 are associated with CHD in the Chinese population, but the association between the SNPs of FOG2 locus and the development of CHD has not been found yet.

Molecule-Doped Nickel Oxide: Verified Charge Transfer and Planar Inverted Mixed Cation Perovskite Solar Cell.

Both conductivity and mobility are essential to charge transfer by carrier transport layers (CTLs) in perovskite solar cells (PSCs). The defects derived from generally used ionic doping method lead to the degradation of carrier mobility and parasite recombinations. In this work, a novel molecular doping of NiOx hole transport layer (HTL) is realized successfully by 2,2'-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6TCNNQ). Determined by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy, the Fermi level (EF ) of NiOx HTLs is increased from -4.63 to -5.07 eV and valence band maximum (VBM)-EF declines from 0.58 to 0.29 eV after F6TCNNQ doping. The energy level offset between the VBMs of NiOx and perovskites declines from 0.18 to 0.04 eV. Combining with first-principle calculations, electrostatic force microscopy is applied for the first time to verify direct electron transfer from NiOx to F6TCNNQ. The average power conversion efficiency of CsFAMA mixed cation PSCs is boosted by ≈8% depending on F6TCNNQ-doped NiOx HTLs. Strikingly, the champion cell conversion efficiency of CsFAMA mixed cations and MAPbI3 -based devices gets to 20.86% and 19.75%, respectively. Different from passivation effect, the results offer an extremely promising molecular doping method for inorganic CTLs in PSCs. This methodology definitely paves a novel way to modulate the doping in hybrid electronics more than perovskite and organic solar cells.

Worldwide prevalence of adverse pregnancy outcomes associated with in vitro fertilization/intracytoplasmic sperm injection among multiple births: a systematic review and meta-analysis based on cohort studies.

PURPOSE: To perform a systematic review and meta-analysis of reported estimates of adverse pregnancy outcomes among multiple births conceived with in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). METHODS: PubMed, Google Scholar, Cochrane Libraries and Chinese databases were searched through May 2016 for cohort studies assessing adverse pregnancy outcomes associated with IVF/ICSI multiple births. Random-effects meta-analyses were used to calculate pooled estimates of adverse pregnancy outcomes and, where appropriate, heterogeneity was explored in group-specific analyses. RESULTS: Sixty-four studies, with 60,210 IVF/ICSI multiple births and 146,737 spontaneously conceived multiple births, were selected for analysis. Among IVF/ICSI multiple births, the pooled estimates were 51.5% [95% confidence interval (CI): 48.7-54.3] for preterm birth, 12.1% (95% CI: 10.4-14.1) for very preterm birth, 49.8% (95% CI: 47.6-52.0) for low birth weight, 8.4% (95% CI: 7.1-9.9) for very low birth weight, 16.2% (95% CI: 12.9-20.1) for small for gestational age, 3.0% (95% CI: 2.5-3.7) for perinatal mortality and 4.7% (95% CI: 4.0-5.6) for congenital malformations. When the data were restricted to twins, the pooled estimates also showed a high prevalence of adverse outcomes. There was a similar prevalence of poor outcomes among multiple births conceived with IVF/ICSI and naturally (all P ≥ 0.0792). Significant differences in different continents, countries, and income groups were found. CONCLUSIONS: The IVF/ICSI multiple pregnancies have a high prevalence of adverse pregnancy outcomes. However, population-wide prospective adverse outcomes registries covering the entire world population for IVF/ICSI pregnancies are needed to determine the exact perinatal prevalence.

Single-dose intra-articular bupivacaine plus morphine versus bupivacaine alone after arthroscopic knee surgery: a meta-analysis of randomized controlled trials.

PURPOSE: The purpose of this meta-analysis was to compare the efficacy and safety of single-dose intra-articular bupivacaine plus morphine versus bupivacaine alone for pain management following arthroscopic knee surgery. METHOD: A comprehensive literature search was conducted to identify randomized controlled trials that used single-dose intra-articular bupivacaine plus morphine and bupivacaine alone for post-operative pain, using MEDLINE (1966-2014), Cochrane Library and EMBASE databases. The weighted mean difference (WMD), relative risk (RR) and their corresponding 95 % confidence intervals (CIs) were calculated using RevMan statistical software. RESULT: A total of twenty-nine trials (n = 1167) were included. The post-operative visual analog scale (VAS) pain score of the bupivacaine plus morphine group compared with the bupivacaine alone group was significantly lower (WMD -1.15, 95 % CI -1.67 to -0.63, p < 0.0001). As far as safety, there was no significant difference in side effects between the two groups (RR 1.10, 95 % CI 0.59-2.04, n.s.). Sensitivity analyses suggested that the results of these two primary outcomes were stable and reliable. However, the current evidence did not suggest a superior effect with respect to the time to first analgesic request (WMD 51.33, 95 % CI -110.99 to 213.65, n.s.) and the number of patients requiring supplementary analgesia (RR 1.13, 95 % CI 0.92-1.39, n.s.). CONCLUSIONS: On the basis of the currently available literature, this study is the first to suggest that single-dose intra-articular bupivacaine plus morphine was shown to be significantly better than bupivacaine alone at relieving post-operative pain after arthroscopic knee surgery without increasing the short-term side effects. Routine use of single-dose intra-articular bupivacaine plus morphine is an effective way for pain management after arthroscopic knee surgery. LEVEL OF EVIDENCE: II.

Worldwide prevalence of adverse pregnancy outcomes among singleton pregnancies after in vitro fertilization/intracytoplasmic sperm injection: a systematic review and meta-analysis.

PURPOSE: The worldwide prevalence of adverse pregnancy outcomes (APOs) in singleton pregnancies after in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) is suggested to vary; however, a complete overview is missing. The aim of this review is to estimate the worldwide prevalence of APOs associated with IVF/ICSI singleton pregnancies. METHODS: PubMed, Google Scholar, Cochrane Libraries, and Chinese databases were searched for studies assessing APOs among IVF/ICSI singleton births through March 2016. The prevalence estimates were summarized and analyzed by meta-analysis. RESULTS: Fifty-two cohort studies, with 181,741 IVF/ICSI singleton births and 4,636,508 spontaneously conceived singleton births, were selected for analysis. Among IVF/ICSI singleton pregnancies, pooled estimates were 10.9% [95% confidence interval (CI) 10.0-11.8] for preterm birth, 2.4% (95% CI 1.9-3.0) for very preterm birth, 8.7% (95% CI 7.4-10.2) for low birth weight, 2.0% (95% CI 1.5-2.6) for very low birth weight, 7.1% (95% CI 5.5-9.2) for small for gestational age, 1.1% (95% CI 0.9-1.3) for perinatal mortality, and 5.7% (95% CI 4.7-6.9) for congenital malformations. The IVF/ICSI singleton pregnancies have higher prevalence of APOs compared with those conceived naturally (all P = 0.000). Significant differences in different continents, countries, income groups, and type of assisted conception were found. CONCLUSIONS: The IVF/ICSI singleton pregnancies are at a higher prevalence of adverse perinatal outcomes compared with those conceived naturally. Important geographical differences were found. Yet, population-wide prospective APO registries covering the entire world population for IVF/ICSI pregnancies are needed to determine the exact perinatal prevalence.

Guidelines for Developing and Reporting Machine Learning Predictive Models in Biomedical Research: A Multidisciplinary View.

BACKGROUND: As more and more researchers are turning to big data for new opportunities of biomedical discoveries, machine learning models, as the backbone of big data analysis, are mentioned more often in biomedical journals. However, owing to the inherent complexity of machine learning methods, they are prone to misuse. Because of the flexibility in specifying machine learning models, the results are often insufficiently reported in research articles, hindering reliable assessment of model validity and consistent interpretation of model outputs. OBJECTIVE: To attain a set of guidelines on the use of machine learning predictive models within clinical settings to make sure the models are correctly applied and sufficiently reported so that true discoveries can be distinguished from random coincidence. METHODS: A multidisciplinary panel of machine learning experts, clinicians, and traditional statisticians were interviewed, using an iterative process in accordance with the Delphi method. RESULTS: The process produced a set of guidelines that consists of (1) a list of reporting items to be included in a research article and (2) a set of practical sequential steps for developing predictive models. CONCLUSIONS: A set of guidelines was generated to enable correct application of machine learning models and consistent reporting of model specifications and results in biomedical research. We believe that such guidelines will accelerate the adoption of big data analysis, particularly with machine learning methods, in the biomedical research community.

Prognostic value and predictive threshold of tumor volume for patients with locally advanced nasopharyngeal carcinoma receiving intensity-modulated radiotherapy.

BACKGROUND: Gross target volume of primary tumor (GTV-P) is very important for the prognosis prediction of patients with nasopharyngeal carcinoma (NPC), but it is unknown whether the same is true for locally advanced NPC patients treated with intensity-modulated radiotherapy (IMRT). This study aimed to clarify the prognostic value of tumor volume for patient with locally advanced NPC receiving IMRT and to find a suitable cut-off value of GTV-P for prognosis prediction. METHODS: Clinical data of 358 patients with locally advanced NPC who received IMRT were reviewed. Receiver operating characteristic (ROC) curves were used to identify the cut-off values of GTV-P for the prediction of different endpoints [overall survival (OS), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS)] and to test the prognostic value of GTV-P when compared with that of the American Joint Committee on Cancer T staging system. RESULTS: The 358 patients with locally advanced NPC were divided into two groups by the cut-off value of GTV-P as determined using ROC curves: 219 (61.2%) patients with GTV-P ≤46.4 mL and 139 (38.8%) with GTV-P >46.4 mL. The 3-year OS, LRFS, DMFS, and DFS rates were all higher in patients with GTV-P ≤46.4 mL than in those with GTV-P > 46.4 mL (all P < 0.05). Multivariate analysis indicated that GTV-P >46.4 mL was an independent unfavorable prognostic factor for patient survival. The ROC curve verified that the predictive ability of GTV-P was superior to that of T category (P < 0.001). The cut-off values of GTV-P for the prediction of OS, LRFS, DMFS, and DFS were 46.4, 57.9, 75.4 and 46.4 mL, respectively. CONCLUSION: In patients with locally advanced NPC, GTV-P >46.4 mL is an independent unfavorable prognostic indicator for survival after IMRT, with a prognostic value superior to that of T category.

Association among dietary magnesium, serum magnesium, and diabetes: a cross-sectional study in middle-aged and older adults.

BACKGROUND: A number of studies have reported the association between magnesium (Mg) and diabetes. However, the various conclusions were inconsistent and the data on the Chinese population was limited. The objective of this study was to evaluate the association among dietary Mg, serum Mg, and diabetes in Chinese adults. METHODS: A cross-sectional study that contained 2904 subjects was conducted. Biochemical test results and dietary intakes of subjects were collected for analysis. The adjusted odds ratios (ORs) and the corresponding 95 % confidence intervals (95 % CIs) were used to determine the relationship between Mg status and diabetes by logistic regression. RESULTS: The prevalence of diabetes of the investigated population was 10.1 %. Dietary Mg intake was not significantly correlated with diabetes (P > 0.05). The significant negative association between serum Mg and diabetes existed, and the multivariate adjusted OR was 0.34 (95 % CI 0.24, 0.49) in model 3 for the highest quartile of serum Mg compared with the lowest. The P values for trend were all less than 0.001 for the relationship between serum Mg and diabetes. Dietary Mg intake and serum Mg were not significantly correlated in the diabetes population (P = 0.936). CONCLUSIONS: Dietary Mg was not significantly correlated with diabetes, while serum Mg was inversely correlated with diabetes in the Chinese population. Meanwhile, dietary Mg intake and serum Mg were not significantly correlated in the diabetes population.

Association between serum selenium level and type 2 diabetes mellitus: a non-linear dose-response meta-analysis of observational studies.

BACKGROUND: The association between serum selenium levels and type 2 diabetes mellitus (T2DM) is controversial. We performed a systematic review and non-linear dose-response meta-analysis of observational studies to investigate the association in the present study. METHODS: A comprehensive literature search was conducted using MEDLINE and EMBASE databases. A pooled odds ratio (OR) and related 95 % confidence interval (95 % CI) for T2DM between the highest and lowest serum selenium categories, and a non-linear dose-response relationship between selenium and T2DM were estimated. RESULTS: A total of five studies (of 13,460 participants) were identified as meeting the inclusion criteria. The pooled OR indicated that there was a significantly higher prevalence of T2DM in the highest category of blood selenium compared with the lowest (OR = 1.63, 95 % CI: 1.04-2.56, P = 0.033). Moreover, a significant non-linear dose-response relationship was observed between serum selenium levels and T2DM (P < 0.001). Serum selenium levels were positively associated with T2DM in populations with relatively low serum selenium levels (<97.5 µg/l) and those with high serum selenium levels (>132.5 µg/l). CONCLUSIONS: The positive association between serum selenium levels and T2DM existed in populations with relatively low levels and high levels of serum selenium, indicating a likely U-shaped non-linear dose-response relationship between serum selenium and T2DM.