Systematic Review Of Epidemiological Studies Research Articles

Benzene Exposure and Lung Cancer Risk: A Systematic Review and Meta-Analysis of Human Studies.

Lung cancer is a leading cause of death with nearly 1.8 million deaths estimated worldwide in 2020. Although benzene is classified as a human carcinogen (Group 1) on the basis of its association with acute myeloid/non-lymphocytic leukaemia, there is still limited evidence that it may influence lung cancer risk. This study examined the potential link between benzene exposure and risk of lung cancer using a systematic review of epidemiological studies and meta-analysis. We searched through PubMed, Web of Science and Scopus databases up to 10 February 2023 to identify all articles on the association between benzene exposure and lung cancer (incidence or prevalence) and/or mortality. We extracted the risk estimates of the highest and the lowest reported categories of benzene exposure and conducted a meta-analysis using a random-effects model. Heterogeneity and publication bias were analysed using an I2 test and funnel plots asymmetry, respectively. Twenty-one studies were included in the final analysis, with a total of 10,750 lung cancer cases and 2899 lung cancer deaths. Overall, risk estimates of lung cancer prevalence and mortality in association with benzene exposure were 1.20 (n = 14; 95% CI 1.05-1.37) and 1.15 (n = 13; 95% CI 1.02-1.30), respectively. In all cases, heterogeneity was quite large, while no significant publication bias was observed. When only studies that adjusted for smoking habit were selected, the risk for lung cancer increased by up to 34% (n = 9; 95% CI 1.10-1.64). Our data, which show a strong association between benzene exposure and lung cancer risk, may have important public health implications. However, further studies are needed to identify the lung cancer risk associated with benzene exposure considering different smoking conditions.

Huntington's disease prevalence in Asia: a systematic review and meta-analysis.

The epidemiological studies on Huntington's disease (HD) in the Asian population suggest that prevalence rates are significantly lower than in the Western population. We conducted a systematic review of epidemiological studies of HD in Asia to compare the level of impact of the disease on the Asian population. Original articles and reviews about HD prevalence in the Asian population were found through databases such as Embase, Medline, and PsychInfo. Relevant articles were analysed by scrutinising of references, including specific key words. A meta-analysis was performed on prevalence rates to find the degree of similarities with I2. Point Prevalence was measured as the number of people affected by HD in a 100,000 population and expressed as Point Prevalence (PP)= Number of people affected/100,000 with 95% Confidence Intervals (CI95). Results from the random-effect meta-analysis show the highest point prevalence of HD in the Middle East with PP=4.0 (CI95=2.90-5.30). The lowest point prevalence was found in the Chinese population with PP=0.25 (CI95=0.16-0.36). Europe remains at a high prevalence compared to Asian countries with PP=1.00 (CI95=0.82-1.19). The overall prevalence in Asia is PP=0.70 (CI95=0.44-1.0). Our study reveals that HD disease affects the population of Asia to a lesser extent than in Europe. The plausible explanation for differences in prevalence is that in some countries, the affected individuals will not self-refer to HD screening for fear of social stigma, negative influence in marriage, and lack of genetic and neurological testing. Another explanation is that studies that used genetic testing exclusively were able to identify the CAG repeats, subgroups of CAG repeat A1 & A2, and haplogroup C, which has less predisposition to high HD prevalence in Asians compared to the Caucasian population.

A Systematic Review of Epidemiologic Studies on Scabies in the Philippines

A Systematic Review of Epidemiologic Studies on Scabies in the Philippines

Association of vitamin D levels with anthropometric and adiposity indicators across all age groups: a systematic review of epidemiologic studies.

It has not been established whether vitamin D deficiency is associated with anthropometric state; therefore, this systematic review examined the relationship between serum vitamin D levels with anthropometrics and adiposity across different ages. Studies that examined vitamin D deficiency with adiposity measures in different age groups were searched in the PubMed, Scopus, Embase, and Google Scholar databases until November 2023. Two investigators independently reviewed titles and abstracts, examined full-text articles, extracted data, and rated the quality in accordance with the Newcastle-Ottawa criteria. Seventy-two studies, with a total of 59,430 subjects, were included. Of these studies, 27 cross-sectional studies and one longitudinal study (with 25,615 participants) evaluated the possible link between 25(OH)D serum concentrations and anthropometric/adiposity indices in the pediatric population. Forty-two cross-sectional studies and two cohort investigations (with 33,815 participants) investigated the relationship between serum 25(OH)D levels and adiposity measures in adults and/or the elderly population. There is evidence supporting links between vitamin D deficiency and obesity, and revealed an inverse association between vitamin D and adiposity indicators, specifically in female subjects. However, the effects of several confounding factors should also be considered. Most published studies, most of which were cross-sectional, reported a negative association between vitamin D and female adiposity indicators. Therefore, serum vitamin D levels should be monitored in overweight/obese individuals.

PFAS Exposures and the Human Metabolome: A Systematic Review of Epidemiological Studies.

There is a growing interest in understanding the health effects of exposure to per- and polyfluoroalkyl substances (PFAS) through the study of the human metabolome. In this systematic review, we aimed to identify consistent findings between PFAS and metabolomic signatures. We conducted a search matching specific keywords that was independently reviewed by two authors on two databases (EMBASE and PubMed) from their inception through July 19, 2022 following PRISMA guidelines. We identified a total of 28 eligible observational studies that evaluated the associations between 31 different PFAS exposures and metabolomics in humans. The most common exposure evaluated was legacy long-chain PFAS. Population sample sizes ranged from 40 to 1,105 participants at different stages across the lifespan. A total of 19 studies used a non-targeted metabolomics approach, 7 used targeted approaches, and 2 included both. The majority of studies were cross-sectional (n = 25), including four with prospective analyses of PFAS measured prior to metabolomics. Most frequently reported associations across studies were observed between PFAS and amino acids, fatty acids, glycerophospholipids, glycerolipids, phosphosphingolipids, bile acids, ceramides, purines, and acylcarnitines. Corresponding metabolic pathways were also altered, including lipid, amino acid, carbohydrate, nucleotide, energy metabolism, glycan biosynthesis and metabolism, and metabolism of cofactors and vitamins. We found consistent evidence across studies indicating PFAS-induced alterations in lipid and amino acid metabolites, which may be involved in energy and cell membrane disruption.

Per- and Polyfluoroalkyl Substances and Breastfeeding as a Vulnerable Function: A Systematic Review of Epidemiological Studies.

Milk formation in the breast during breastfeeding is a complex hormonally regulated process, potentially sensitive to the effects of endocrine-disrupting chemical exposures. The environmental chemicals, per- and polyfluoroalkyl substances (PFAS) are known endocrine disruptors. PFAS exposure have been associated with insufficient mammary gland development in mice and reduced breastfeeding duration in humans. The aim of this review was to gather the epidemiological evidence on the association between PFAS exposure and breastfeeding duration. Using PubMed and Embase, we performed a systematic literature search (on 23 January 2023) to identify epidemiological studies examining the association between maternal PFAS exposure and breastfeeding duration. Animal studies, reviews, and non-English studies were excluded. The risk of bias was assessed using the risk of bias in non-randomized studies of exposures tool. Estimates describing the association between PFAS exposure and the duration of breastfeeding were identified, and the data were synthesized separately for each type of PFAS and for the duration of exclusive and total breastfeeding. Six studies with between 336 and 2374 participants each were identified. PFAS exposure was assessed in serum samples (five studies) or based on residential address (one study). Five out of six studies found shorter total duration of breastfeeding with higher PFAS exposure. The most consistent associations were seen for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA). The finding of a potential causal association between PFAS exposure and breastfeeding duration is in agreement with findings from experimental studies.

PFAS exposures and the human metabolome: a systematic review of epidemiological studies

PFAS exposures and the human metabolome: a systematic review of epidemiological studies

The Prevalence of Idiopathic or Inherited Isolated Dystonia: A Systematic Review and Meta‐Analysis

ABSTRACTBackgroundA systematic review of epidemiological studies of primary dystonia from 1985 and 2010 found an overall prevalence of 16.43 per 100,000 (95% CI = 12.09–22.32).MethodsWe performed a systematic review of studies from 2010 and 2022 to determine if there are important differences in epidemiology between these time periods.ResultsNineteen studies were included. Incidence of cervical dystonia, blepharospasm, and oromandibular dystonia were each reported in one study; one study reported incidence for all adult onset idiopathic focal dystonias combined. Using data from 11 studies, we performed random effects meta‐analyses of the prevalence of cervical dystonia (9.95 per 100,000; 95% CI = 3.51–28.17), blepharospasm (2.82 per 100,000; 95% CI = 1.12–7.12), laryngeal dystonia (0.40 per 100,000; 95% CI = 0.09–1.83), upper limb dystonia (1.27 per 100,000; 95% CI = 0.36–4.52), oromandibular dystonia (0.57 per 100,000; 95% CI = 0.15–2.15), and idiopathic or inherited isolated dystonia all subtypes combined (30.85 per 100,000; 95% CI = 5.06–187.74). All studies reported more cases of dystonia in females. There was no significant difference in prevalence by subgroup analysis based on time of study publication (1985–2010 vs. 2010–2022). Subgroup analysis of differences in prevalence by dystonia subtype by continent using all studies published (1985–2022) revealed significant regional differences in the prevalence of cervical and laryngeal dystonia.ConclusionThe incidence and prevalence of idiopathic or inherited isolated dystonia in the last decade was not significantly different from earlier reports. Population‐based studies across multiple geographic areas are needed to obtain a clearer understanding of the epidemiology of this condition.

A systematic review on solid fuel combustion exposure and respiratory health in adults in Europe, USA, Canada, Australia and New Zealand.

Epidemiological studies performed in low- and middle-income countries have shown a positive association between solid fuel burning exposure and adverse health effects, including respiratory effects in adults. However, the evidence is less clear in other countries. We performed a systematic review of epidemiological studies conducted in Europe, North America (Canada and USA only), Australia and New Zealand on the association between outdoor and indoor exposure to solid fuel (biomass and coal) combustion and respiratory outcomes in adults. We identified 34 articles. The epidemiological evidence is still limited. Positive associations were found between indoor coal, wood and combined solid fuel combustion exposure and lung cancer risk, although based on a limited number of studies. A significant association was found between indoor solid fuel exposure and COPD risk. Inconsistent results were found considering indoor coal, wood and mixed solid fuel burning exposure and other respiratory outcomes (i.e. lower respiratory infections, upper respiratory infections and other upper respiratory tract diseases, asthma and respiratory symptoms). Inconsistent results were found considering the relationship between the exposure to outdoor wood burning exposure and overall respiratory mortality, asthma, COPD and respiratory symptoms in adults. The available epidemiological evidence between outdoor exposure to residential coal burning and respiratory outcomes suggests an increased risk of adverse respiratory effects. The studies considering the impact of the introduction of measures in order to reduce solid fuel burning on air quality and health showed an improvement in air quality resulting in a reduction of adverse respiratory effects. The identified epidemiological studies have several limitations. Additional and better conducted epidemiological studies are needed to establish whether exposure occurring indoors and outdoors to solid fuel combustion pollutants is associated with adverse respiratory outcomes in adults.

Association of Pneumococcal Serotype With Susceptibility to Antimicrobial Drugs: A Systematic Review and Meta-analysis.

Pneumococcal serotypes differ in antimicrobial susceptibility. However, patterns and causes of this variation are not comprehensively understood. We undertook a systematic review of epidemiologic studies of pneumococci isolated from carriage or invasive disease among children globally from 2000-2019. We evaluated associations of each serotype with nonsusceptibility to penicillin, macrolides, and trimethoprim/sulfamethoxazole. We evaluated differences in the prevalence of nonsusceptibility to major antibiotic classes across serotypes using random-effects meta-regression models and assessed changes in prevalence of nonsusceptibility after implementation of pneumococcal conjugate vaccines (PCVs). We also evaluated associations between biological characteristics of serotypes and their likelihood of nonsusceptibility to each drug. We included data from 129 studies representing 32 187 isolates across 52 countries. Within serotypes, the proportion of nonsusceptible isolates varied geographically and over time, in settings using and those not using PCVs. Factors predicting enhanced fitness of serotypes in colonization as well as enhanced pathogenicity were each associated with higher likelihood of nonsusceptibility to penicillin, macrolides, and trimethoprim/sulfamethoxazole. Increases in prevalence of nonsusceptibility following PCV implementation were evident among non-PCV serotypes, including 6A, 6C, 15A, 15B/C, 19A, and 35B; however, this pattern was not universally evident among non-PCV serotypes. Postvaccination increases in nonsusceptibility for serotypes 6A and 19A were attenuated in settings that implemented PCV13. In pneumococci, nonsusceptibility to penicillin, macrolides, and trimethoprim/sulfamethoxazole is associated with more frequent opportunities for antibiotic exposure during both prolonged carriage episodes and when serotypes cause disease. These findings suggest multiple pathways leading to resistance selection in pneumococci.

Cortisol Co-Secretion and Clinical Usefulness of ACTH Stimulation Test in Primary Aldosteronism: A Systematic Review and Biases in Epidemiological Studies.

The hypothalamus-pituitary-adrenal (HPA) axis plays an important role in primary aldosteronism. Aldosterone biosynthesis is regulated not only by angiotensin II in the renin-angiotensin-aldosterone system, but also by adrenocorticotropic hormone (ACTH), one of the key components of the HPA axis. Although previous studies have reported cortisol cosecretion in primary aldosteronism, particularly aldosterone-producing adenoma (APA), the clinical relevance of such aldosterone and cortisol cosecretion from APA and hypertension or other metabolic disorders has not been fully established. Several somatic mutations including KCNJ5 and CACNA1D are known to induce autonomous production of aldosterone in APA, and the aldosterone responsiveness to ACTH may vary according to each mutation. The ACTH stimulation test has been reported to be a useful tool to distinguish the subtypes of primary aldosteronism (e.g., unilateral vs bilateral) in some studies, but it has not been commonly applied in clinical practice due to limited evidence. Given the recent advancement of imaging, omics research, and computational approach, it is important to summarize the most updated evidence to disentangle the potential impact of cortisol excess in primary aldosteronism and whether the ACTH stimulation test needs to be considered during the diagnostic process of primary aldosteronism. In this article, we conducted a systematic review of epidemiological studies about (i) cortisol cosecretion in primary aldosteronism and (ii) the ACTH stimulation test for the diagnosis of primary aldosteronism (including subtype diagnosis). Then, we discussed potential biases (e.g., confounding bias, overadjustment, information bias, selection bias, and sampling bias) in the previous studies and introduced some advanced epidemiological/statistical methods to minimize these limitations. A better understanding of biases and epidemiological perspective on this topic would allow us to produce further robust evidence and balanced discussion about the causal mechanisms involving the HPA axis and clinical usefulness of the ACTH stimulation test among patients with primary aldosteronism.

Association between prenatal phthalate exposure and gestational metabolic syndrome parameters: a systematic review of epidemiological studies.

The relationship of intrauterine phthalate exposure with gestational metabolic syndrome (GMS) parameters is inconsistently reported. We performed a systematic review to evaluate the association between prenatal phthalate exposure and GMS parameters. A literature search was performed in three databases. According to the defined PECOS statement, eligible studies were identified. The method and result for each study was qualitatively summarized with great emphasis on study design and exposure assessment. Fourteen studies were included in the present systematic review. Two studies used one-spot serum sample for evaluation of phthalate exposure, while others used 1-4 urine samples. Concentrations of phthalate metabolites varied substantially, and the levels in serum were greatly lower than those in urine. These studies observed no interstudy or intrastudy consistency for association between phthalates and GMS in pregnant women cross-sectionally or longitudinally, regardless of phthalates species or GMS indicator. Most reported associations were not significantly different from null result. Besides, positive and negative relationships also existed. The current epidemiological data do not support the hypothesis that prenatal exposure to phthalates increases GMS risk.

Exposure to non-persistent pesticides and puberty timing: a systematic review of the epidemiological evidence

Numerous modern non-persistent pesticides have demonstrated estrogenic/anti-androgenic activity and have been classified as endocrine-disrupting chemicals (EDCs). Processes involved in puberty development are vulnerable to EDCs, such as compounds that interfere with the metabolism or activity of sex steroids. To conduct a systematic review of epidemiological studies on the relationship between early-life exposure to non-persistent pesticides and puberty timing and/or sexual maturation in girls and boys. A systematic search was carried out using MEDLINE and SCOPUS databases, including original articles published up to November 2020. Thirteen studies were selected after excluding non-original and non-human studies. Exposure to different types of pesticides has been associated with altered puberty timing in girls and/or boys in eight studies. In utero exposure to atrazine has been related to earlier age of menarche in girls; exposure to organophosphate (OP) pesticides has been related to delayed sexual development in boys and girls; childhood pyrethroid exposure has been associated with pubertal delay in girls and pubertal advancement in boys; and prenatal/childhood exposure to multiple pesticides has been linked to earlier puberty onset in girls and pubertal delay in boys. Most of the reviewed studies describe a relationship between pesticide exposure and changes in the age of puberty onset or sex hormone levels, although the quality of the evidence is generally low. Further well-designed longitudinal studies are warranted on specific classes of pesticides and on possible interactions between different types of compounds.

Current risk of breast implant-associated anaplastic large cell lymphoma: a systematic review of epidemiological studies.

Recent epidemiological studies have attempted to accurately determine the risk of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). However, comparisons of previously published works are difficult due to widespread variations in reporting. We systematically review the epidemiology in order to better define the current risk of BIA-ALCL. Herein, we report the global epidemiology with an emphasis on the U.S. breast implant population while simultaneously assessing the oncologic safety of smooth-surface devices. In the current manuscript, a systematic review of PubMed and other scientific databases, as well as the grey literature, was conducted for epidemiologic studies on BIA-ALCL. Using analytical and descriptive epidemiology, we estimated the cumulative incidence and incidence rate of BIA-ALCL using a standardized approach. Cumulative incidence was reported at implant and patient-specific levels. The patient-specific cumulative risk within the U.S. market ranges from 1.79 per 1,000 (1:559) to 2.82 per 1,000 (1:355) patients with a textured implant. The implant-specific risk of Allergan textured devices ranges from 1:602–871 to 1:8,500, while the risk of commercially available Mentor Siltex implants is 1:50,000. No epidemiological study or regulatory agency reported a case of BIA-ALCL occurring exclusively with a smooth device. As such, with the removal of Allergan textured breast devices, this study demonstrates substantial gaps in the epidemiological knowledge of BIA-ALCL, including the current risk of commercially available textured breast implants in the U.S. market. Although the risk of BIA-ALCL is low, surgeons should exercise extreme caution when considering the use of a textured breast device for cosmetic or reconstructive purposes.

Epidemiological Studies of Low-Dose Ionizing Radiation and Cancer: Rationale and Framework for the Monograph and Overview of Eligible Studies.

Whether low-dose ionizing radiation can cause cancer is a critical and long-debated question in radiation protection. Since the Biological Effects of Ionizing Radiation report by the National Academies in 2006, new publications from large, well-powered epidemiological studies of low doses have reported positive dose-response relationships. It has been suggested, however, that biases could explain these findings. We conducted a systematic review of epidemiological studies with mean doses less than 100 mGy published 2006-2017. We required individualized doses and dose-response estimates with confidence intervals. We identified 26 eligible studies (eight environmental, four medical, and 14 occupational), including 91 000 solid cancers and 13 000 leukemias. Mean doses ranged from 0.1 to 82 mGy. The excess relative risk at 100 mGy was positive for 16 of 22 solid cancer studies and 17 of 20 leukemia studies. The aim of this monograph was to systematically review the potential biases in these studies (including dose uncertainty, confounding, and outcome misclassification) and to assess whether the subset of minimally biased studies provides evidence for cancer risks from low-dose radiation. Here, we describe the framework for the systematic bias review and provide an overview of the eligible studies.

Mycotoxin exposure and human cancer risk: A systematic review of epidemiological studies.

In recent years, there has been an increasing interest in investigating the carcinogenicity of mycotoxins in humans. This systematic review aims to provide an overview of data linking exposure to different mycotoxins with human cancer risk. Publications (2019 and earlier) of case-control or longitudinal cohort studies were identified in PubMed and EMBASE. These articles were then screened by independent reviewers and their quality was assessed according to the Newcastle-Ottawa scale. Animal, cross-sectional, and molecular studies satisfied criteria for exclusion. In total, 14 articles were included: 13 case-control studies and 1 longitudinal cohort study. Included articles focused on associations of mycotoxin exposure with primary liver, breast, and cervical cancer. Overall, a positive association between the consumption of aflatoxin-contaminated foods and primary liver cancer risk was verified. Two case-control studies in Africa investigated the relationship between zearalenone and its metabolites and breast cancer risk, though conflicting results were reported. Two case-control studies investigated the association between hepatocellular carcinoma and fumonisin B1 exposure, but no significant associations were observed. This systematic review incorporates several clear observations of dose-dependent associations between aflatoxins and liver cancer risk, in keeping with IARC Monograph conclusions. Only few human epidemiological studies investigated the associations between mycotoxin exposures and cancer risk. To close this gap, more in-depth research is needed to unravel evidence for other common mycotoxins, such as deoxynivalenol and ochratoxin A. The link between mycotoxin exposures and cancer risk has mainly been established in experimental studies, and needs to be confirmed in human epidemiological studies to support the evidence-based public health strategies.

Health effects of living near an incinerator: A systematic review of epidemiological studies, with focus on last generation plants

Huge reductions in incinerators' emissions occurred over time, and results of older studies cannot be directly generalized to modern plants. We conducted a systematic review of the epidemiologic evidence of the health effects of incinerators, classifying plants in three generations, according to emission limits.A systematic search identified 63 epidemiologic studies, published in English, investigating health effects of incinerators on humans. We focused on cancer, cardio-cerebrovascular diseases (CVD) and respiratory diseases, pregnancy outcomes and congenital anomalies. Only six studies in the general population were on third generation incinerators providing data on pregnancy outcomes and congenital anomalies. Given the heterogeneity of methods, the abundance of ecological/semi-ecological studies and the lack of reliable quantitative measures of exposure in several studies we did not perform any meta-analysis.No excesses emerged concerning all cancers and lung cancer. An excess of non-Hodgkin lymphoma was reported in some earlier studies, but not for second generation plants. Possible excesses of soft tissue sarcomas were confined to earlier incinerators and the areas closer to the plants. No clear association emerged for CVD and diseases of the respiratory system. Several different pregnancy outcomes were considered, and no consistent association emerged, in spite of a few positive results. Studies were negative for congenital anomalies as a whole. Sporadic excesses were reported in a few studies for specific types of anomalies, but no consistent pattern emerged. Evaluation of the evidence was hindered by heterogeneity in reporting and classification of outcomes across studies.Direct evidence from third generation plants is scarce. Methodological issues in study design (mainly related to exposure assessment, confounding and ecological design) and analysis make interpretation of results complex. In spite of this, the overall evidence suggests that, if there were any excesses at all for older incinerators, they were modest at most. Additional monitoring of third generation plants needs to overcome methodological weaknesses.

Bushfire smoke: urgent need for a national health protection strategy.

This research was undertaken with support from the Australian National University College of Health and Medicine, and the assistance of resources from the Centre for Air pollution, energy and health Research (CAR). We used the CAR Data and Analysis Technology platform (https://cardat.github.io) to analyse data

Situation analysis of onchocerciasis in Cameroon: a protocol for systematic review of epidemiological studies and impact of disease control interventions

BackgroundMany control methods have been implemented to tackle onchocerciasis and great successes have been achieved, leading to a paradigm shift from control of morbidity to interruption of transmission and ultimately elimination. The mandate of the African Programme for Onchocerciasis Control (APOC) ended in 2015, and endemic countries are to plan and conduct elimination activities by themselves, with technical assistance by the Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN). To this end, an elimination expert committee was set up in Cameroon in 2018. This committee identified the need to update the data on the current situation of onchocerciasis. The present study aims to systematically review and report all available epidemiological data, including prevalence, intensity and transmission of onchocerciasis to provide pertinent information that will be useful to design optimal strategies to achieve onchocerciasis elimination in Cameroon.MethodsPubMed/MEDLINE, EMBASE and Web of Science will be searched from inception onwards. Grey literature will be identified through Google Scholar searches, dissertation databases and other relevant documents such as government reports. Eligible studies will be mostly observational, including cohort and cross-sectional surveys. No limitations will be imposed on publication status and study period. The primary outcomes will be (1) the prevalence and intensity of Onchocerca volvulus infection in humans, (2) transmission intensity and (3) impact of interventions on prevalence, intensity and transmission of onchocerciasis. Secondary outcomes will be environmental and socio-demographic factors supporting the primary outcomes. Two reviewers will independently screen all citations, full-text articles and abstract data. Potential conflicts will be resolved through discussion. Methodological quality including bias will be appraised using appropriate approaches. A narrative synthesis will describe quality and content of the epidemiological evidence. Prevalence and intensity of infection estimates will be stratified according to gender, age, geographical location and year of publication.DiscussionThis study will provide the health authorities as well as the scientific community with up-to-date information about the epidemiological situation of onchocerciasis in Cameroon. Understanding the spatiotemporal dynamics of the infection will help to define alternative and complementary strategies to accelerate onchocerciasis elimination in the country. Results of this review will also be used to update existing epidemiological models for onchocerciasis in order to fine-tune predictions of elimination timeframes in the country.Systematic review registrationThis protocol is under registration review in PROSPERO.

Particulate Matter Exposure and Attention-Deficit/Hyperactivity Disorder in Children: A Systematic Review of Epidemiological Studies.

Attention-deficit/hyperactivity disorder (ADHD) is the most common cognitive and behavioural disorder affecting children, with a worldwide-pooled prevalence of around 5%. Exposure to particulate matter (PM) air pollution is suspected to be associated with autism spectrum disorders and recent studies have investigated the relationship between PM exposure and ADHD. In the absence of any synthesis of the relevant literature on this topic, this systematic review of epidemiological studies aimed to investigate the relationship between the exposure of children to PM and ADHD and identify gaps in our current knowledge. In December 2018, we searched the PubMed and EMBASE databases. We only included epidemiological studies carried out on children without any age limit, measuring PM exposure and health outcomes related to ADHD. We assessed the quality of the articles and the risk of bias for each included article using the Newcastle–Ottawa Scale and the Office of Health Assessment and Translation (OHAT) approach, respectively. The keyword search yielded 774 results. Twelve studies with a total number of 181,144 children met our inclusion criteria, of which 10 were prospective cohort studies and 2 were cross-sectional studies. We subsequently classified the selected articles as high or good quality studies. A total of 9 out of the 12 studies reported a positive association between PM exposure to outdoor air pollution and behavioral problems related to attention. Despite these results, we found a significant degree of heterogeneity among the study designs. Furthermore, 11 studies were judged to be at a probably high risk of bias in the exposure assessment. In conclusion, we opine that further high quality studies are still needed in order to clarify the association between PM exposure and ADHD diagnosis.