Comparison of Serum Folate between Schizophrenic Patients and Healthy Controls in Chinese Han Adult Population: A Systematic Review and Meta-Analysis.

AIM AND OBJECTIVE: To assess the relationship between serum folate and schizophrenia (SZ) risk in the Chinese Han adult population in different papers, a systematic review and metaanalysis were conducted. MATERIALS AND METHODS: We searched for this meta-analysis on three English databases (PubMed, Embase, and Web of science) and four Chinese databases (CNKI, SinoMed, Wanfang, and CQVIP) on March 27, 2021. INCLUSION CRITERIA: studies provided folate levels in serum of cases and controls as mean and standard deviation. EXCLUSION CRITERIA: subjects were not Chinese Han adult population. The Newcastle-Ottawa Scale score was used to assess the risk of bias in the included studies. Standard mean difference (SMD) was used to measure the difference between SZ patients and healthy controls. Subgroup analyses by measurement time, duration, and age were performed, respectively. RESULTS: This meta-analysis included 19 publications involving 1571 SZ cases and 1283 healthy controls. In total studies, the pooled result showed that SZ patients had decreased serum folate levels compared with healthy controls (SMD [95%CI] = -1.37[-1.83,-0.90], PSMD<0.001), and in most of the subgroups, the associations reached decreased significantly; while in the subgroup of drugs use, the association was not reached significantly. CONCLUSION: Dose-response analysis and subgroup analyses by gender were not performed due to the lack of data. Folate deficiency is associated with the patients, and antipsychotic drugs might have positive effects on improving serum folate levels in Chinese Han adult SZ.

Serum folate, vitamin B12 levels and diabetic peripheral neuropathy in type 2 diabetes: A meta-analysis.

The association between serum folate and vitamin B12 levels and the risk of diabetic peripheral neuropathy (DPN) remains unclear. This meta-analysis included 16 studies of serum folate levels (1190 cases and 1501 controls) and 18 studies of serum vitamin B12 levels (1239 cases and 1562 controls) in patients with type 2 diabetes mellitus (T2DM). Reduced serum levels of folate and vitamin B12 were found in patients with T2DM and DPN compared with patients with T2DM but without DPN; weighted mean difference (WMD) = -1.64 (95% confidence interval [CI] = -2.46, -0.81) and WMD = -70.86 (95% CI = -101.55, -40.17), respectively. A subgroup analysis confirmed these associations in the Chinese population, but not in the Caucasian and mixed populations. In conclusion, these findings support the need for further controlled studies in defined patient populations and the importance of monitoring serum folate and vitamin B12 levels in patients with T2DM.

Glutathione S-transferase M1 polymorphisms and Parkinson's disease risk: a meta-analysis.

OBJECTIVES: Studies examining whether glutathione S-transferase M1 (GSTM1) polymorphisms are associated with Parkinson's disease (PD) have reported inconsistent results. To clarify those inconsistencies, a meta-analysis was performed. METHODS: The electronic databases were searched for all publications regarding the association. Studies were included if they met the eligibility criteria. The strength of the association between GSTM1 polymorphisms and PD risk was measured by odds ratios (ORs) and 95% confidence intervals (CIs) in the recessive genetic model (null genotype vs. present genotype). Subgroup analyses by ethnicity and OR type were performed. RESULTS: A total of 22 publications (23 studies) were included. There were 14, 7 and 2 studies with Caucasians, Asians and Latinos, respectively. OR types were 15 and 8 studies with crude and adjusted ORs, respectively. The combined results of the overall analysis showed that the GSTM1 null genotype was not significantly associated with PD risk (ORrandom-effects = 1.06, 95% CI = 0.95-1.19). In subgroup analyses by ethnicity, no significant associations were found in Caucasians, Asians or Latinos individually. Similarly, there were no associations in the subgroup analyses by OR type. There were no obvious publication biases in any of the comparisons. DISCUSSION: The results of this meta-analysis suggest that the GSTM1 null genotype is not significantly associated with PD risk.

Serum folate levels in schizophrenia: A meta-analysis.

To clarify the relationship between serum folate and schizophrenia (SZ) risk, the meta-analysis was conducted. PubMed, Embase, and Web of Science were searched without language restrictions. Weighted mean difference (WMD) as a summary statistic was used in this meta-analysis. Subgroup analyses by publication language (English and non-English), ethnicity (Caucasian, Asian, African, Latino, and mixed population), duration (acute, chronic, patients including both acute and chronic SZ, and not mentioned about either chronic or acute), measurement time (before drugs using and after drugs using), gender (male and female) and age (<50 years old and >50 years old) were performed. Power analysis was also conducted to detect the reliability of the meta-analyses' results. In summary, the subgroups which failed to detect significant decreased associations were always with lower statistic power and could not be confirmed. The results supported that decreased serum folate was associated with SZ risk in total studies and subgroups of English publications, Caucasians, Asians, acute SZ patients, measurement after drugs using in SZ patients, and age<50 with the great enough powers, respectively. In conclusion, the present meta-analysis found that folate deficiency is associated to SZ, and subgroups which did not reach enough statistical power need further investigation in the future.

Null genotype of GSTT1 contributes to increased Parkinson's disease risk in Caucasians: evidence from a meta-analysis.

Conflicting results in previous case-control studies on the association between Glutathione S-transferase T1 (GSTT1) gene polymorphism and Parkinson's disease (PD) risk have been reported, so we conducted this meta-analysis. We searched and extracted data from 3 Chinese and 3 English web-based electronic databases to evaluate the associations by odds ratio (OR) and its 95% confidence interval (CI) under the recessive genetic comparison model (null genotype vs. present genotype). We also conducted subgroup analyses by ethnicity and adjusted status of OR, respectively. Meta-analyses and subgroup analyses of larger studies (sample size ≥300) were also reanalyzed. When 18 eligible studies (3,963 PD cases and 5,472 controls) were pooled to analyze the association, we found no statistically significant result (OR 1.24, 95% CI 0.96-1.60). In the subgroup analyses by ethnicity, there was statistically significant association between the null genotype of GSTT1 and PD risk among Caucasians, while the associations were not found among Asians and Latinos. In the subgroup analyses by adjusted status of OR, there were no significant associations both in studies with crude OR and adjusted OR. Meta-analyses and subgroup analyses of larger studies (sample size ≥300) were also confirmed the associations mentioned above. Power analysis indicated only meta-analysis of Caucasians had enough evidence to claim the association. In conclusion, the meta-analysis suggests that the null genotype of GSTT1 contributes to PD risk in Caucasians, and no association in Asians is needed more studies to confirm.

Serum 25-hydroxyvitamin D and breast cancer risk: a meta-analysis of prospective studies.

There were some case-control studies, nested case-control studies, and cohort studies with controversial results on the association between serum 25-hydroxyvitamin D [25(OH)D] and breast cancer risk. Case-control studies are prone to selection bias, which limit the strength and quality of the evidence. To overcome the shortcoming of the case-control studies, the meta-analysis of prospective studies including nested case-control studies and cohort studies was conducted. PubMed, Embase, and Web of Science databases were searched, and the last retrieval date was March 24, 2013. For the highest versus the lowest level of serum 25(OH)D, the relative risks (RRs) and its 95% confidence intervals (CIs) from each study were used to estimate summary RR and its 95% CI. Subgroup analyses by geographic region, menopausal status, and adjusted status of RR were also performed, respectively. A dose-response association between serum 25(OH)D concentration and breast cancer risk was assessed. Fourteen articles with 9,110 breast cancer cases and 16,244 controls were included in the meta-analysis. Overall, serum 25(OH)D levels were inversely significantly associated with breast cancer risk (RR = 0.845, 95% CI = 0.750-0.951). Inversely statistically significant associations were observed in North American studies, postmenopausal women, and studies with adjusted and unadjusted RR, respectively. No statistically significant associations were observed in European studies and premenopausal women, respectively. Dose-response analysis showed that every 10 ng/mL increment in serum 25(OH)D concentration was associated with a significant 3.2% reduction in breast cancer risk. This meta-analysis provides evidence of a significantly inverse association between serum 25(OH)D concentration and breast cancer risk.

GSTM1 and GSTT1 polymorphisms and colorectal cancer risk in Chinese population: a meta-analysis.

PURPOSE: Studies investigating the associations between GSTM1 and GSTT1 polymorphisms and colorectal cancer (CRC) risk in Chinese population have reported controversial results. Thus, a meta-analysis was performed. METHODS: Four hundred and seven relevant records were identified through a literature search up to September 7, 2011, and 19 studies were finally included, involving a total of 3,130 CRC cases and 6,423 controls. Subgroup analyses were performed by language and study design. Statistical analysis was performed with the software programs Review Manager (version 5.1.2) and STATA (version 11.0). RESULTS: For the GSTM1 polymorphism, the null genotype of GSTM1 was not associated with CRC risk in Chinese population (OR = 1.12, 95% CI = 0.97-1.28). Similar associations were found for GSTT1 polymorphism (OR = 1.10, 95% CI = 0.94-1.29) and the dual null genotype of GSTM1/GSTT1 (OR = 1.26, 95% CI = 0.93-1.71). For subgroup analyses, studies published in English and population-based studies further identified these associations for the three aspects above in Chinese population. CONCLUSIONS: This meta-analysis suggests that the null genotypes of GSTM1 and GSTT1 and the dual null genotype of GSTM1/GSTT1 were all not risk factors in CRC in Chinese population.

[Application of Stata software to test heterogeneity in meta-analysis method].

To introduce the application of Stata software to heterogeneity test in meta-analysis. A data set was set up according to the example in the study, and the corresponding commands of the methods in Stata 9 software were applied to test the example. The methods used were Q-test and I2 statistic attached to the fixed effect model forest plot, H statistic and Galbraith plot. The existence of the heterogeneity among studies could be detected by Q-test and H statistic and the degree of the heterogeneity could be detected by I2 statistic. The outliers which were the sources of the heterogeneity could be spotted from the Galbraith plot. Heterogeneity test in meta-analysis can be completed by the four methods in Stata software simply and quickly. H and I2 statistics are more robust, and the outliers of the heterogeneity can be clearly seen in the Galbraith plot among the four methods.