Nd:YVO4/YVO4 cascaded Raman laser pumped dual-wavelength signal wave MgO:PPLN-OPO with wide range adjustable wavelength interval.

This article presents a dual-wavelength signal wave output system capable of generating a broad range of adjustable wavelength intervals. The setup involved the creation of a dual-wavelength cascaded Raman laser featuring composite cavities operating at 1176 nm and 1313 nm. Experimental investigations were carried out on an external cavity MgO:PPLN-OPO driven by the cascaded Raman laser. By setting the crystal polarization period to 27.6-34.4 µm and the temperature to 50-130°C, adjustable tunable output of dual-wavelength signal wave at 1176 nm-MgO:PPLN-OPO (1550-2294 nm) and 1313 nm-MgO:PPLN-OPO (1768-2189 nm) was achieved with a wavelength interval of 0-218 nm. Under the conditions of a period of 34.4 µm, temperature of 90°C, and an incident Raman power of 2.6 W, the highest conversion efficiency of Raman to dual-wavelength signal wave (2212, 2182 nm) was 34.2%. Furthermore, the maximum output power of dual-wavelength signal wave was recorded at 1.02 W with an incident Raman power of 3.33 W.

Construction and Simulation of High-Quality Development of China's Resource-Based Cities Driven by Innovation Based on System Dynamics.

Innovation is the primary driving force for development; the high-quality development of resource-based cities is ultimately driven by innovation. We constructed an innovation-driven high-quality development system for resource-based cities, including resource, economic, social, and environmental subsystems; according to the interaction between the internal elements of each subsystem, a dynamic model of the innovation-driven high-quality development system of resource-based cities was established, and we selected policy adjustment variables to simulate six policy scenarios. Thus, we simulated high-quality development trends from 2008 to 2035. The results indicate that the policy scenario of increasing innovation investment can promote high-quality development; the policy of increasing innovation investment has a significant effect on economic growth, while it damages the urban ecological environment, and the ideal policy scenario is the environmental priority mode, which appropriately increases innovation investment and reasonably allocates it within the system.

Identification of distinct blood-based biomarkers in early stage of Parkinson's disease.

Parkinson's disease (PD) is a slowly progressive geriatric disease, which can be one of the leading causes of serious socioeconomic burden in the aging society. Clinical trials suggest that prompt treatment of early-stage Parkinson's disease (EPD) may slow down the disease progress and have a better response. Therefore, conducting proteomics study to identify biomarkers for the diagnosis and disease-modifying therapies of EPD is vital. We aimed at identifying distinct protein autoantibody biomarkers of EPD by using the database of GSE62283 based on the platform GPL13669 downloaded from Gene Expression Omnibus database. Differentially expressed proteins (DEPs) between the EPD group (n = 103) and the normal control (NC) group (n = 111) were identified by protein-specific t test. Cluster analysis of DEPs was conducted by protein-protein interaction network to detect hub proteins. The hub proteins were then evaluated to determine the distinct biomarkers by principal component analysis, as well as functional and pathway enrichment analysis. Their biological functions were confirmed by gene ontology functional (GO) and Kyoto encyclopedia of genes and genomes pathway enrichment (KEGG). Two biomarkers, mitochondrial ribosome recycling factor (MRRF) and ribosomal protein S18 (RPS18), distinguished the EPD samples from the NC samples, and they were regarded as high-confidence distinct protein autoantibody biomarkers of EPD. The most significant GO function was protein serine/threonine kinase activity (GO: 0004674) and most of DEPs were enriched in ATP binding in molecular function category (GO: 0005524). These results may help in establishing the prompt and accurate diagnosis of EPD and may also contribute to develop mechanism-based treatments.

Evolution of the Raman beam quality in a folded-coupled-cavity Nd:YVO4/YVO4 Raman laser.

An end-pumped actively $Q$Q-switched ${\rm Nd}\!:\!{{\rm YVO}_4}/{{\rm YVO}_4}$Nd:YVO4/YVO4 Raman laser with a folded coupled cavity is demonstrated to study the evolution of Raman beam quality. The theoretical mechanism of the beam cleanup effect of stimulated Raman scattering is analyzed. The beam quality ($M^2$M2) of the Raman beam and the fundamental beams before and after the Raman conversion are measured experimentally. The results show that with the incident pump power increasing, the ${M^2}$M2 of the fundamental beam increases from 1.85 to 3.08, while the ${M^2}$M2 of the Raman beam increases from 1.21 to 1.69. The beam quality of the Raman laser and its degradation are better than that of the fundamental laser.

IL-18 induced IL-23/IL-17 expression impairs Aß clearance in cultured THP-1 and BV2 cells.

Recent studies have provided overwhelming evidence of the involvement of microglia-related molecular networks in the pathogenesis of Alzheimer's diseases (AD). The potential involvement of pro-inflammatory cytokines interleukin (IL)-18, IL-23 and IL-17 on amyloid (Aß) clearance is still unclear. In this study, we addressed that there might be a net relationship among IL-18, IL-23, and IL-17 and they can affect Aß clearance in cultured macrophage/microglia cells. In human macrophage cell line THP-1, Aß42 incubation could increase the expression of IL-18, IL-23 and IL-17 in a concentration dependent manner. THP-1 cell could clear Aß42 in the culture medium time-dependently, but its capacity of Aß clearance was impaired by IL-18, IL-23 or IL-17 treatment. Similarly, the capacity of the microglia cell line BV2 to clear Aß42 was impaired by IL-18, IL-23 or IL-17 treatment. In co-cultures of BV2 with APP/PS1 neuron, Aß was efficiently cleared by BV2 cell, but Aß clearance was impaired by IL-18, IL-23 or IL-17 treatment. The effects of IL-18, IL-23 and IL-17 could be blocked by their corresponding neutralizing antibodies. In addition, the inhibitory effects of IL-18 were blocked by IL-23 or IL-17 neutralizing antibodies while the inhibitory effects of IL-23 were blocked by IL-17 neutralizing antibodies. Our study provides evidences showing that amyloid induced IL-18/IL-23/IL-17 axis could impair macrophage and microglia-mediated Aß clearance. Thus, IL-18/IL-23/IL-17 axis might be a therapeutic target in AD.

TRPC6 mRNA levels in peripheral leucocytes of patients with Alzheimer's disease and mild cognitive impairment: A case-control study.

BACKGROUND: Transient receptor potential canonical (TRPC) 6 inhibits Aß in Alzheimer's disease (AD) mouse brain and improves the behavioral performance. AIMS: To evaluate the association of TRPC6 expression in peripheral leucocytes from AD and mild cognitive impairment (MCI) patients and to explore its potential value in early diagnosis of AD. METHODS: TRPC6 mRNA levels in peripheral leucocytes were detected by quantitative real-time PCR. The Spearman correlation test was used to ascertain the associations between TRPC6 and the scores of MMSE, ADL, CSDD, CDR. The Receiver Operating Characteristic (ROC) curve was drawn to evaluate the diagnostic potential of TRPC6 for AD and MCI. RESULTS: There were 108 CE, 136 MCI, 164 Con and 60 PD in the study. The expression of TRPC6 mRNA level in peripheral leucocytes was significantly lower: 1) in patients with AD and MCI compared to Con; 2) in AD compared to MCI; 3) in hospitalized AD compared to AD from communities. There was a significantly positive correlation between TRPC6 mRNA and MMSE score (p = .001, R = 0.327). Significantly inverse correlations were found between TRPC6 and CDR score (p < 0.001, R = -0.303) as well as between TRPC6 and ADL score (p = .001, R = -0.342) for all AD. The area under curve of ROC was 0.881 for the classification of AD, and 0.706 for the classification of MCI, respectively. CONCLUSION: TRPC6 expression is inversely correlated with cognitive performance of AD. TRPC6 in peripheral leucocytes may be a potential biomarker for the diagnosis of AD.

Association of neck circumference and cognitive impairment among Chinese elderly.

Objectives: To investigate the association between neck circumference (NC) and cognitive impairment and interactions between relevant variables to the risk of cognitive impairment. Methods: A population-based survey was conducted among elderly inhabitants aged 60 years and over from a community in Shanghai suburb. Multivariate logistic regression analyses were performed to evaluate associations and log likelihood ratio tests to examine interactions. Results: Cognitive impairment was identified in 269 (10.8%) subjects from 2,500 participants. Higher BMI (OR = 1.55; 95% CI = 1.11-2.16), higher WHR (OR = 1.44; 95% CI = 1.07-1.95), and higher total cholesterol (TC) (OR = 1.52; 95% CI = 1.09-2.13) were significantly associated with the increased risk of cognitive impairment. Significant interactions were observed between TC and a few other relevant variables, respectively. Conclusions: NC was associated with the high risk of cognitive impairment. Additive effects of NC with TC on cognitive impairment were observed.

Serum haptoglobin in Chinese patients with Alzheimer's disease and mild cognitive impairment: A case-control study.

BACKGROUND: Serum level of Haptoglobin (Hp) maybe associated with Alzheimer's disease (AD) and mild cognitive impairment (MCI). OBJECTIVE: To investigate associations between serum Hp and AD, as well as between Hp and MCI. METHODS: Serum levels of Hp were measured and analyzed for 51 patients with AD, 139 patients with MCI and their healthy controls matched with sex and age. All study subjects were from a survey among residents aged 60 years and over in a community located in the southwest suburb of Shanghai. RESULTS: Serum levels of Hp were observed significantly higher in AD and MCI cases than controls (both p < 0.0001). A significant positive correlation was found between Hp and Activities of Daily Living (ADL) score (rs = 0.430, p = 0.007), as well as between Hp and Clinical Dementia Rating (CDR) score (rs = 0.359, p = 0.027) in all AD patients. According to the receiver operating characteristic (ROC) curve analysis, the optimal cut-off point for Hp was found to be 67.50 µg/ml (sensitivity, 0.902; specificity, 0.745) in AD patients, and 44.76 µg/ml (sensitivity, 0.986; specificity, 0.403) in MCI patients. CONCLUSION: Elevated serum levels of Hp were observed in AD and MCI patients than controls. In addition, Hp may correlate with the severity of AD.

Metabolic Syndrome and Mild Cognitive Impairment: A Case-Control Study among Elderly in a Shanghai Suburb.

BACKGROUND: Metabolic syndrome (MetS) maybe associated with mild cognitive impairment (MCI). OBJECTIVE: To investigate the relationship between MetS, with its individual or combined components, and MCI among elderly. METHODS: A case-control study was conducted among the elderly aged 65 years and over in a community located in the southwestern suburb of Shanghai, China. The Chinese version of the Mini-Mental Status Examination (C-MMSE) was used to screen subjects with MCI. Associations of MetS with its individual or combined components and MCI were analyzed using conditional regression analyses with or without adjustment for gender, education, current smoking, current drinking, and physical activities. RESULTS: There were 379 subjects with MCI and 379 gender- and age-matched healthy controls in the study. Compared with healthy controls in univariate analyses, subjects with MCI were more likely to have less time spent on physical activity, lower C-MMSE score, heavier weight, larger waistline and hipline, higher diastolic blood pressure, higher body mass index, higher abdominal obesity index, higher serum glycated hemoglobin, higher serum triglycerides, higher serum cholesterol, higher serum uric acid, and higher serum alanine aminotransferase. After multivariable adjustment, MetS was significantly associated with an increased risk of MCI (OR = 2.277; 95% CI: 1.086-4.773). Among MetS components, abdominal obesity (OR = 2.101; 95% CI: 1.224-3.608) and hypertension (OR = 2.075; 95% CI: 1.170-3.678) showed a significant association with MCI, respectively; while these two components were combined, the association was stronger (OR = 2.459; 95% CI: 1.360-4.447). CONCLUSION: MetS and its components, particularly abdominal obesity and hypertension, were found to be significantly associated with the risk of MCI.

Peripheral Blood MicroRNA Expression Profiles in Alzheimer's Disease: Screening, Validation, Association with Clinical Phenotype and Implications for Molecular Mechanism.

A series of investigations have been performed regarding microRNA (miRNA, miR) of Alzheimer's disease (AD) patients. However, most of these used microarray with neither validation by PCR nor any follow-up on the biological mechanism implicated by findings. Further, there were rarely any analyses linking clinical phenotype of de novo, drug-naive patients to cellular pathogenic mechanism(s) to date. Microarray screening followed by validation via quantitative PCR (Q-PCR) assays and the relationship between miRNAs and phenotypic indices were evaluated. Additionally, the cellular mechanism of miRNAs through effects of ß-site amyloid precursor protein (APP) cleaving enzyme (BACE1) was assessed. We identified 2 specific differentially expressed (DE) miRNAs (miR-339 and miR-425) as potential diagnostic biomarkers for AD and revealed that these DE miRNAs could be involved in modulating the pathogenesis of AD via BACE1 protein inhibition. The findings presented here reveal a detailed snapshot of the profile of peripheral blood mononuclear cells (PBMC) miRNA changes in AD patients, association with clinical phenotype, and potential roles in cellular pathogenesis.

Increased serum levels of interleukin-18, -23 and -17 in Chinese patients with Alzheimer's disease.

AIMS: To evaluate the serum levels of interleukin (IL)-18, IL-23 and IL-17 in Chinese patients with Alzheimer's disease (AD), and explore correlations between the three cytokines and relevant parameters. METHODS: Serum concentrations of IL-18, IL-23 and IL-17 were measured by ELISA for 53 AD patients and 53 sex- and age-matched healthy controls in a community of elderly individuals in a Shanghai suburb. RESULTS: Serum concentrations of IL-18, IL-23 and IL-17 were significantly higher in AD patients than controls. The serum level of IL-23 was observed to be significantly higher (p = 0.049) in female AD patients than male AD patients. In addition, a significantly inverse correlation was found between IL-18 and MMSE score (rs = -0.356, p = 0.011) for all AD patients. CONCLUSION: Elevated IL-18, IL-23 and IL-17 levels are observed in AD patients and differences may exist between males and females. Besides, IL-18 may correlate with the severity of AD.

Cognitive impairment among elderly individuals in Shanghai suburb, China: association of C-reactive protein and its interactions with other relevant factors.

OBJECTIVES: To investigate the association between serum C-reactive protein (CRP) concentration and cognitive impairment as well as interactions between CRP and other relevant factors. METHODS: Patients with cognitive impairment and 1 to 2 age- and sex-matched controls nested from a population-based study among residents aged 60 years and older in Shanghai suburb. The associations of serum CRP concentration and other relevant factors were examined with logistic regression analysis. RESULTS: The mean CRP in patients with cognitive impairment was higher than that in controls (P < .001). The highest quartile of CRP (>4.77 mg/L), abdomen obesity, hypertriglyceridemia, and hyperglycemia was associated with cognitive impairment. Significant interactions were found between increased CRP and hypertriglyceridemia as well as between increased CRP and hyperglycemia on cognitive impairment; and the attributable proportion due to interaction was 82% (P < .0001) and 37% (P = .007), respectively. CONCLUSIONS: Increased CRP was associated with cognitive impairment, and additive effects of increased CRP with hypertriglyceridemia and hyperglycemia on cognitive impairment were observed among elderly individuals.

Dementia among elderly in Shanghai suburb: a rural community survey.

The number of elderly in the world is increasing rapidly, especially in China. The prevalence of dementia among elderly was investigated in a community of Sheshan town, located in the Southwest suburb of Shanghai, China. Face-to-face interviews were conducted to collect relevant information with prepared questionnaires. The Chinese version of the Mini-Mental Status Examination was used to screen subjects with cognitive impairment (CI). Physical examinations and neuropsychological assessments were carried out. Dementia and its major subtypes, Alzheimer's disease (AD) and vascular dementia (VaD), were diagnosed by senior neurologists according to relevant diagnostic criteria. In addition, magnetic resonance imaging and EEG (with P300) were performed for a number of cases with AD or VaD. There were 1,472 participants (666 males and 806 females) aged 60 years and over in the study. A total of 167 subjects with CI were screened. Among them, dementia was recognized in 79 cases with a prevalence of 5.37% (95% confidence intervals: 4.22%-6.52%). The diagnosis of AD was made for 53 cases (16 males and 37 females) with a prevalence of 3.60% (95% confidence intervals: 2.65%-4.55%), and VaD for 21 cases (5 males and 16 females) with a prevalence of 1.43% (95% confidence intervals: 0.82%-2.03%); while the ratio of AD to VaD was 2.52. The prevalence rates of dementia among elderly from our study are higher than that previously reported from China, but in line with that reported from most world regions. A nationwide survey and surveillance system on the prevalence of dementia is recommended.

Suicide mortality trends in the Nordic countries 1980-2009.

BACKGROUND AND AIM: The Nordic countries provide a suitable setting for comparing trends in suicide mortality. The aim of this report is to compare suicide trends by age, gender, region and methods in Denmark, Finland, Iceland, Norway and Sweden 1980-2009. METHODS: Suicide statistics 1980-2009 were analyzed for men and women aged 15 years and above and the age group 15-24 years. Regional suicide rates in 2009 were presented in maps. RESULTS: The suicide rates across the Nordic countries declined from 25-50 per 100,000 in 1980 to 20-36 in 2009 for men and from 9-26 in 1980 to 8-11 in 2009 for women. The rates in Finland were consistently higher than those of the other countries. A significant increase of suicides in young women in Finland and Norway and a lack of a decline among young women in Sweden were noted. The male- female ratio of suicide converged to approximately 3:1 across the region during the study period. Rural areas in Finland, Norway and Sweden saw the highest suicide rates, whereas the rates in the capital regions of Denmark, Norway and Sweden were lower than the respective national rates. CONCLUSIONS: We hold that the overall decline of suicide rates in the Nordic countries reflects the socio-economic development and stability of the region, including the well-functioning healthcare. The increasing rates in Finland and Norway and the unchanged rate in Sweden of suicide in young women are an alarming trend break that calls for continued monitoring.

The association of weight status with cognitive impairment in the elderly population of a Shanghai suburb.

OBJECTIVE: A population-based survey was conducted to analyze the association of under-weight, blood pressure, glucose and lipid metabolism with cognitive impairment in people, 60 years and over, living in 2 towns of Shanghai. METHODS: Face-to-face interviews were carried out to collect relevant information with questionnaires. Anthropometric indices of height, weight, waist circumference (WC) and hip circumference were measured. Multivariable logistic regression analyses were performed to evaluate the association of weight status with cognitive impairment. RESULTS: Cognitive impairment were diagnosed in 198 (7.0%) of the 2 809 participants. Compared to the normal BMI category, the under-weight category was significantly associated with the risk of cognitive impairment (OR= 2.47, 95%CI: 1.46-5.23). Subjects with a high WC were 1.5 times (OR= 1.42, 95%CI: 1.10-2.67) more likely and subjects with a high WHR were 1.7 times (OR= 1.68, 95%CI: 1.05-2.84) more likely to be associated with cognitive impairment than the subjects in the reference group. This study demonstrates a significant interaction between hypertension, lipid disorder and WC or WHR on the risk of cognitive impairment in a rural population in Shanghai. CONCLUSIONS: Central obesity was significantly associated with the risk of cognitive impairment. A low BMI may be a risk factor for cognitive impairment. A significant interaction between hypertension, lipid disorder and WC or WHR on the risk of cognitive impairment in Shanghai rural population was found.

Serum level of interleukin-6 in Chinese patients with multiple sclerosis.

The aim of this study was to investigate the serum concentration of interleukin (IL)-6 in patients with relapsing-remitting MS (RR-MS), compare the difference between males and females, and explore the correlation between the serum concentration of IL-6 and clinical parameters like the current age, the age at onset, disease duration, disability (expanded disability status scale, EDSS), and the number of relapse. We compared the serum concentration of IL-6 in 39 patients with MS and 39 healthy controls matched with sex and age. The serum IL-6 concentration was measured by FlowCytomix. Compared to healthy controls, both the frequency of subjects with detectable level of IL-6 (P=0.005) and the serum concentration of IL-6 (P=0.004) were significantly higher in MS patients. When data were analyzed by gender, statistical significances between MS patients and healthy controls were observed only in females, although the frequency with detectable level and the serum concentration of IL-6 were higher in male MS patients than male controls. The serum level of IL-6 was found to be significantly positively correlated with the number of relapse for female MS patients (r(s)=0.511, P=0.009), with the current age for male MS patients (r(s)=0.700, P=0.005), and with the age at onset for all MS patients (r(s)=0.351, P=0.028). Our results may support that IL-6 is involved in the pathogenesis of MS and indicate that differences exist between male and female patients.

Serum levels of interleukin (IL)-18, IL-23 and IL-17 in Chinese patients with multiple sclerosis.

It has been reported that cytokines play an important role in the pathogenesis of multiple sclerosis (MS). The aim of this study was to evaluate the serum levels of interleukin (IL)-18, IL-23 and IL-17 in Chinese patients with MS. We compared the serum concentrations of pro-inflammatory cytokines IL-18, IL-23 and IL-17 in 39 patients with MS and 39 healthy controls matched with sex and age. Serum cytokines were measured by FlowCytomix, a kind of cytometric bead-based assay. Correlations between the serum levels of the three cytokines and disability (expanded disability status scale, EDSS), disease duration, current age and age at onset were examined. Serum concentrations of all IL-18, IL-23 and IL-17 were significantly higher in MS patients than healthy controls. There were no significant differences of the three cytokines' levels between female and male healthy controls, while the serum IL-18 level was observed significantly higher (P=0.049) in male MS patients than female MS patients. No significant correlations were observed between any of the three cytokines' levels and EDSS, disease duration and current age. However, IL-23 was found negatively correlated with age at onset in male MS patients (r(s)=-0.775, P=0.041). Our data suggest that all IL-18, IL-23 and IL-17 may be involved in the pathogenesis of MS. However, the relationships of the three cytokines and clinical characteristics of MS need to be further investigated in the future.

Evaluation of anthropometric indices for metabolic syndrome in Chinese adults aged 40 years and over.

BACKGROUND: The prevalence of metabolic syndrome (MetS) is increasing worldwide with a marked impact in cardiovascular disease (CVD) and diabetes risk. AIM OF THE STUDY: To evaluate the anthropometric indices for metabolic syndrome (MetS) and determine the optimal cut-off values of waist circumference (WC), body mass index (BMI), and waist height ratio (WHtR) for MetS in Chinese adults aged 40 years and over. METHODS: A sample of Chinese adults aged 40 years and over including 430 men and 638 women was investigated. Blood pressure, weight, height, and WC were measured; HDL-cholesterol (HDL-C), Triglyceride (TG), and plasma glucose were examined. Receiver operating characteristics (ROC) curve analyses were used to evaluate the optimal cut-off point of WC, BMI, and WHtR for MetS. RESULTS: According to the ROC curve analysis, the optimal cut-off point for WC was found to be 84.0 cm in men and 80.0 cm in women; for BMI, it was 26.0 in men and 25.0 in women; and for WHtR, it was 0.5 in both men and women. WHtR has the highest predictive value for fast plasma glucose in women, while BMI has the better prediction of dyslipidemia in men. CONCLUSIONS: Anthropometric indices (WC, BMI, and WHtR) are useful screening tools for obesity, MetS, and CVD risk factors. BMI may be a better indicator than the others for screening obesity, dyslipidemia, and other risk components in Chinese men aged 40 years and over, while WHtR may be better for Chinese women, especially among those aged 70 years and over.

Serotonin transporter gene polymorphism in Chinese patients with poststroke depression: a case-control study.

BACKGROUND AND PURPOSE: We sought to compare the distribution of the serotonin transporter gene SLC6A4 polymorphism between depressed and nondepressed poststroke patients. METHODS: Patients with cerebral stroke admitted to hospital during a 1-year period were enrolled in a 1:1 case-control study. All cases and controls were genotyped for polymorphism of the serotonin transporter-linked promoter region and the single-nucleotide polymorphism rs25531. RESULTS: Among 367 patients with cerebral stroke, 57 (15.5%) were diagnosed with poststroke depression at 1 month after stroke. In the patients with poststroke depression, 7 genotypes of the serotonin transporter gene SLC6A4 were detected, and the frequency of S/S homozygotes was significantly higher (P=0.049) than that in controls. CONCLUSIONS: S/S homozygosity may be positively associated with the occurrence of poststroke depression in Chinese patients.

Glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms, smoking, and their interaction in oral cancer: a HuGE review and meta-analysis.

The association between glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) null polymorphisms and oral cancer is not consistent across studies, and data on their interaction with smoking in oral cancer are lacking. The authors systematically searched PubMed and SciVerse Scopus for case-control studies examining the association between null genotypes of the GSTM1 and GSTT1 genes and oral cancer. Twenty-eight case-control studies published in English were identified. Summary odds ratios were derived via random-effects models. The summary odds ratio for the GSTM1 null genotype was 1.43 in Asians (95% confidence interval (CI): 1.14, 1.78; P < 0.01, I (2) = 73%) and 0.98 in Caucasians (95% CI: 0.76, 1.28; P = 0.91, I (2) = 0%). Case-only analysis of 6 studies (552 cases) showed an inverse multiplicative interaction between GSTM1 null polymorphisms and smoking (ever/high levels of smoking vs. never/low levels) (odds ratio (OR) = 0.51, 95% CI: 0.32, 0.82; P = 0.01, I (2) = 34%). The GSTT1 null genotype was not significantly associated with oral cancer in Asians (OR = 1.07, 95% CI: 0.82, 1.38; P = 0.63, I (2) = 65%) or Caucasians (OR = 1.04, 95% CI: 0.41, 2.65; P = 0.93, I (2) = 55%). In conclusion, the GSTM1 null genotype may be associated with a higher risk of oral cancer in Asians but not in Caucasians, and this effect may be modified by smoking status. The GSTT1 null genotype may not be associated with oral cancer.