Relationship between IL-10 gene -819C/T polymorphism and the risk of inflammatory bowel disease: a meta-analysis.

Background: The -819C/T polymorphism in interleukin 10 (IL-10) gene has been reported to be associated with inflammatory bowel disease (IBD) ,but the previous results are conflicting. Materials and Methods: The present study aimed at investigating the association between this polymorphism and risk of IBD using a meta-analysis.PubMed,Web of Science,EMBASE,google scholar and China National Knowledge Infrastructure (CNKI) databases were systematically searched to identify relevant publications from their inception to April 2016.Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects models. Results: A total of 7 case-control studies containing 1890 patients and 2929 controls were enrolled into this meta-analysis, and our results showed no association between IL-10 gene -819C/T polymorphism and IBD risk(TT vs. CC:OR=0.81,95%CI 0.64- 1.04;CT vs. CC:OR=0.92,95%CI 0.81-1.05; Dominant model: OR=0.90,95%CI 0.80-1.02; Recessive model: OR=0.84,95%CI 0.66-1.06). In a subgroup analysis by nationality, the -819C/T polymorphism was not associated with IBD in both Asians and Caucasians. In the subgroup analysis stratified by IBD type, significant association was found in Crohn���s disease(CD)(CT vs. CC:OR=0.68,95%CI 0.48-0.97). Conclusion: In summary, the present meta-analysis suggests that the IL-10 gene -819C/T polymorphism may be associated with CD risk.

Alcohol consumption and lung cancer risk in never smokers

Objective: The main objective of this study is to analyse the role of alcohol consumption on lung cancer risk in people who have never smoked. Methods: We conducted a systematic review of the scientific literature following the PRISMA statement. We searched Medline, EMBASE and CINAHL using different combinations of MeSH terms and free text. We included cohort studies, pooled cohort studies and case-control studies comprising at least 25 anatomopathologically-confirmed diagnoses of lung cancer cases, a sample size larger than 100 individuals and more than five years of follow-up for cohort studies. We excluded studies that did not specifically report results for never smokers. We developed a quality score to assess the quality of the included papers and we ultimately included 14 investigations with a heterogeneous design and methodology. Results: Results for alcohol consumption and lung cancer risk in never smokers are inconclusive; however, several studies showed a dose-response pattern for total alcohol consumption and for spirits. Heterogeneous results were found for wine and beer. Conclusion: No clear effect is observed for alcohol consumption. Due to the limited evidence, no conclusion can be drawn for beer or wine consumption. There is little research available on the effect of alcohol on lung cancer risk for people who have never smoked, and more studies are urgently needed on this topic.

Drinking water disinfection by-products, genetic polymorphisms, and birth outcomes in a european mother-child cohort study

International audience

Associa����o entre periodontite e artrite reumatoide

Introdu����o: A artrite reumatoide �� uma doen��a inflamat��ria, cr��nica, de etiologia e patog��nese ainda desconhecida, caraterizada pelo envolvimento preferencial da membrana sinovial das articula����o, pelo desenvolvimento de eros��es ��sseas e progressiva destrui����o articular (Fonseca et al., 2002). A periodontite �� uma doen��a infeciosa e cr��nica caraterizada por perda irrevers��vel dos tecidos de suporte periodontais e de osso alveolar (Ziebolz et al., 2002). Liubomorova (1964) foi o primeiro autor a descrever os poss��veis mecanismos inflamat��rios comuns de ambas as doen��as, assistindo-se, nos ��ltimos anos, a um aumento de evid��ncia cient��fica relativa a uma poss��vel associa����o entre a periodontite e a artrite reumatoide. Objetivo: A presente revis��o de literatura teve como objetivo analisar a evid��ncia cient��fica dispon��vel relativa a uma poss��vel associa����o entre a periodontite e a artrite reumatoide, atentando-se em particular �� preval��ncia e severidade da periodontite em pacientes com artrite reumatoide. Materiais e m��todos: Foi realizada uma pesquisa bibliogr��fica na base de dados PubMed, priorizando-se revis��es sistem��ticas e meta-an��lises, estudos coorte e caso-controlo. Foram apenas inclu��dos estudos dispon��veis em ingl��s e publicados entre 2010 a 2016. Resultados: Onze estudos compreenderam os crit��rios para integrar esta revis��o. A grande maioria verificou que pacientes com artrite reumatoide s��o mais suscet��veis a manifestar periodontite e a apresentar piores par��metros periodontais, quando comparados com indiv��duos saud��veis.

Factores asociados al desplazamiento activo en bicicleta al colegio en el Distrito Bogot��, Colombia. Estudio FUPRECOL

Introducci��n: El transporte activo (TA) puede ser una oportunidad para incrementar los niveles de actividad f��sica diarios de los ni��os y adolescentes, adem��s de destacarse como una estrategia pr��ctica, accesible y sostenible a largo plazo. Objetivos: El objetivo del presente estudio es doble: Analizar los patrones de desplazamiento activo en bicicleta al y desde el centro educativo, y b) Identificar los factores asociados al uso de la bicicleta como TA; en una muestra de ni��os y j��venes pertenecientes a escuelas oficiales de Bogot��, Colombia. Material y m��todos: Se trata de un sub-an��lisis del estudio FUPRECOL en 8060 ni��os y adolescentes entre los 9-17 a��os de edad). El modo de desplazamiento del escolar fue determinado a trav��s de la pregunta: �����Durante los ��ltimos 7 d��as, usaste bicicleta para ir al colegio/escuela y volver a la casa?. Dicha respuesta se categoriz�� en activos ���Si��� (si se desplazan en bicicleta) y pasivos ���No��� (si se desplazan en veh��culo motorizado). Se midieron par��metros antropom��tricos de peso, talla y per��metro de cintura. El m��ximo nivel de estudios alcanzados por la madre/padre (no reporta, primaria o secundaria/t��cnico o tecn��logo/universitario o postgrado) y la composici��n del hogar (vive con padre/vive con madre/con ambos padres/con abuelos/otros familiares) se auto-report�� por los padres. Las relaciones entre el TA y los factores anteriormente descritos se analizaron mediante regresi��n log��stica binaria. Resultados: El 21,9% del total de la muestra reporta usar la bicicleta como medio de transporte y el 7,9% acumula m��s de 120 minutos al d��a. Se observ�� una mayor probabilidad de usar la bicicleta como medio de desplazamiento activo a la escuela en los varones, en los j��venes entre 9 y 12 a��os, y en aquellos cuyo padre/madre reportaron mayor grado acad��mico, es decir, ���universitario/postgrado���. 3 Conclusi��n: Los hallazgos del presente estudio sugieren que es necesario promover el TA desde la ni��ez, poniendo mayor ��nfasis en el paso a la adolescencia y en las j��venes, para as�� aumentar los niveles diarios de AF de estos.

Prevalencia y factores asociados al consumo de bebidas azucaradas en escolares de 9 a 17 a��os de Bogot��, Colombia: Estudio FUPRECOL

Objetivo: Determinar la prevalencia y los factores asociados al consumo de bebidas azucaradas en una poblaci��n escolar de Bogot��, Colombia, pertenecientes al estudio FUPRECOL. M��todos: Estudio descriptivo y transversal, realizado en 8136 ni��os y adolescentes en edad escolar entre 9 y 17 a��os de Bogot��, Colombia. El peso, la estatura, el ��ndice de masa corporal (IMC), la circunferencia de cintura y el porcentaje de grasa, se recogieron como marcadores antropom��tricos y de composici��n corporal. El consumo de bebidas azucaradas (bebidas carbonatadas, jugos ultra-procesados y/o T��), y los factores asociados (sexo, edad, obesidad abdominal, clasificaci��n del IMC, grado de estudios de la madre/padre, y nivel nutricional por cuestionario ���Krece plus���), se recogieron por encuesta estructurada. Se establecieron asociaciones mediante la construcci��n de modelos de regresi��n log��stica simple. Resultados: De la poblaci��n general, el 58,4% eran mujeres. En funci��n al sexo, los varones acusaron la mayor ingesta de ���bebidas carbonatadas��� con una frecuencia semanal y diaria de 70,9% y 21,0%, respectivamente, seguido de ���jugos ultra- procesados��� (64,4% semanal vs. 11,3% diario). En ambos sexos, la prevalencia de obesidad abdominal fue mayor en los escolares que respondieron consumir diariamente ���bebidas carbonatadas��� (23,3%), ���jugos ultra-procesados��� (13,2%) y ���bebidas T����� (9,7%). La edad, el grado de educaci��n de los padres y el nivel nutricional, se asociaron como factores predisponentes al consumo diario de ���bebidas carbonatadas���. Conclusi��n: El consumo de bebidas azucaradas cambia por los factores analizados. Se recomiendan intervenciones integrales en las que est��n involucrados los componentes nutricional y educativo entre los ni��os y adolescentes de Bogot��, Colombia.

Modela����o do cancro da mama na regi��o do Alentejo

Estudos epidemiol��gicos s��o estudos estat��sticos onde se procura relacionar ocorr��ncias de eventos de sa��de com uma ou v��rias causas espec��ficas. A import��ncia que os modelos epidemiol��gicos assumem hoje no estudo de doen��as de foro oncol��gico, em particular no estabelecimento das suas etiologias, �� incontorn��vel. Segundo Ogden, J. (1999) o cancro �� "um crescimento incontrol��vel de c��lulas anormais que produzem tumores chamados neoplasias". Estes tumores podem ter origem benigna (n��o se espalham pelo corpo) ou maligna (apresentam metastiza����o de outros ��rg��os). Sendo uma doen��a actual, com uma elevada taxa de incid��ncia em Portugal quando comparada com outras doen��as (Instituto Nacional de Estat��stica- INE, 2009), aumentando esta taxa com a idade tal como refere Marques, L. (2003), podendo ocorrer o diagn��stico desta doen��a em qualquer idade. De acordo com INE (2000) pode dizer-se que o cancro est�� entre as tr��s principais causas de morte em Portugal, registando-se um aumento progressivo do seu peso proporcional, sendo o cancro da mama o tipo de cancro mais comum entre as mulheres e uma das doen��as com maior impacto na nossa sociedade. O objectivo principal deste trabalho �� a estima����o e modela����o do risco de contrair uma doen��a de natureza n��o contagiosa e rara (neste caso, cancro da mama), usando dados da regi��o do Alentejo. Pretende-se fazer um apanhado das metodologias mais empregues nesta ��rea e aplic��-las na pr��tica, com ��nfase nos estudos caso-controlo e nos modelos lineares generalizados (GLM) - mais concretamente regress��o log��stica. Os estudos caso-controlo s��o usados para identificar os factores que podem contribuir para uma condi����o m��dica, comparando indiv��duos que t��m essa condi����o (casos) com pacientes que n��o t��m a condi����o, mas que de resto s��o semelhantes (controlos). Neste trabalho utilizou-se essa metodologia para estudar a associa����o entre o viver em ambiente rural/urbano e o cancro da mama. Tendo em conta que o objectivo principal deste estudo se prende com o estudo da rela����o entre vari��veis, mais propriamente, an��lise de influ��ncia que uma ou mais vari��veis (explicativas) t��m sobre uma vari��vel de interesse (resposta), para esse efeito s��o estudados os modelos lineares generalizados - GLM - unificados na mesma moldura te��rica pela primeira vez por Nelder & Wedderburn (1972) - e, posteriormente aplicados ao conjunto de dados sobre cancro da mama na Regi��o do Alentejo. O presente trabalho pretende assim, ser um contributo na identifica����o de factores de risco do cancro da mama na regi��o do Alentejo. ABSTRACT: Epidemiological studies are statistical studies where attempts to relate occurrences of health events with one or more specific causes. The importance of epidemiological models that are far in the study of diseases of cancer forum, particularly in establishing their etiology, is inescapable. According to Ogden, J. (1999) cancer is "an incontrollable growth of abnormal cells that produce tumors called cancer". These tumors may be benign (not spread throughout the body) or malignant (show metastasis to other organs). Being a current illness with a high incidence rate in Portugal compared with the same respect to other diseases (National Statistics 1nstitute -1NE, 2009) having an increasing rate with age as mentioned Marques, L. (2003), and can possibly be diagnosed at any age. According to 1NE (2000) the cancer is among the top three causes of death in Portugal and there is a progressive increase of its proportional weight. Breast cancer is the most common form of cancer among women and the diseases with major impact in our society. The main objective of this work is to model and estimate the risk of contracting a non-contagious and rare disease (in this case, breast cancer), using data from the Alentejo region. It is intended to summarize some of the methodologies employed in this area and apply them in practice, with emphasis on case-control studies and generalized linear models (GLM) - more specifically the logistic regression. The case-control studies are used to identify factors that may contribute to a medical condition, comparing individuals who have this condition (cases) with patients who have not the condition but that are otherwise similar (controls). ln this work we used this methodology to study the association between living in a rural/urban and breast cancer. Given that the main objective of this study rather relates to the study of the relationship between variables to analyze the influence that one or more variables (explanatory) have on a variable (response), for this purpose we study the generalized linear models - GLM - first unified in the same theoretical framework by Nelder and Wedderburn (1972) and subsequently applied to the data set on breast cancer in the Alentejo region. This work intends to be a contribution in identifying risk factors for breast cancer in the Alentejo region.

Water Delivery Quality and Automatic Control Modes in Irrigation Canals. A Case Study.

Regarding canal management modernization, water savings and water delivery quality, the study presents two automatic canal control approaches of the PI (Proportional and Integral) type: the distant and the local downstream control modes. The two PI controllers are defined, tuned and tested using an hydraulic unsteady flow simulation model, particularly suitable for canal control studies. The PI control parameters are tuned using optimization tools. The simulations are done for a Portuguese prototype canal and the PI controllers are analyzed and compared considering a demand-oriented-canal operation. The paper presents and analyzes the two control modes answers for five different offtake types ��� gate controlled weir, gate controlled orifice, weir with or without adjustable height and automatic flow adjustable offtake. The simulation results are compared using water volumes performance indicators (considering the demanded, supplied and the effectives water volumes) and a time indicator, defined taking into account the time during which the demand discharges are effective discharges. Regarding water savings, the simulation results for the five offtake types prove that the local downstream control gives the best results (no water operational losses) and that the distant downstream control presents worse results in connection with the automatic flow adjustable offtakes. Considering the water volumes and time performance indicators, the best results are obtained for the automatic flow adjustable offtakes and the worse for the gate controlled orifices, followed by the weir with adjustable height.

The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement: Guidelines for reporting observational studies.

Much biomedical research is observational. The reporting of such research is often inadequate, which hampers the assessment of its strengths and weaknesses and of a study's generalisability. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Initiative developed recommendations on what should be included in an accurate and complete report of an observational study. We defined the scope of the recommendations to cover three main study designs: cohort, case-control, and cross-sectional studies. We convened a 2-day workshop in September 2004, with methodologists, researchers, and journal editors to draft a checklist of items. This list was subsequently revised during several meetings of the coordinating group and in e-mail discussions with the larger group of STROBE contributors, taking into account empirical evidence and methodological considerations. The workshop and the subsequent iterative process of consultation and revision resulted in a checklist of 22 items (the STROBE Statement) that relate to the title, abstract, introduction, methods, results, and discussion sections of articles. 18 items are common to all three study designs and four are specific for cohort, case-control, or cross-sectional studies. A detailed Explanation and Elaboration document is published separately and is freely available on the Web sites of PLoS Medicine, Annals of Internal Medicine, and Epidemiology. We hope that the STROBE Statement will contribute to improving the quality of reporting of observational studies.

Gene Set Analysis for improving genetic association studies

Introduction. Genetic epidemiology is focused on the study of the genetic causes that determine health and diseases in populations. To achieve this goal a common strategy is to explore differences in genetic variability between diseased and nondiseased individuals. Usual markers of genetic variability are single nucleotide polymorphisms (SNPs) which are changes in just one base in the genome. The usual statistical approach in genetic epidemiology study is a marginal analysis, where each SNP is analyzed separately for association with the phenotype. Motivation. It has been observed, that for common diseases the single-SNP analysis is not very powerful for detecting genetic causing variants. In this work, we consider Gene Set Analysis (GSA) as an alternative to standard marginal association approaches. GSA aims to assess the overall association of a set of genetic variants with a phenotype and has the potential to detect subtle effects of variants in a gene or a pathway that might be missed when assessed individually. Objective. We present a new optimized implementation of a pair of gene set analysis methodologies for analyze the individual evidence of SNPs in biological pathways. We perform a simulation study for exploring the power of the proposed methodologies in a set of scenarios with different number of causal SNPs under different effect sizes. In addition, we compare the results with the usual single-SNP analysis method. Moreover, we show the advantage of using the proposed gene set approaches in the context of an Alzheimer disease case-control study where we explore the Reelin signal pathway.

Epidemiological studies of childhood and adolescence headache

The main purpose of this study was to examine the changes in the prevalence, incidence, and characteristics of headache in childhood and adolescence. In addition, the predictors of the change in the occurrence of childhood headache and the association between adolescent headache and behavior were studied. The occurrence and characteristics of headache were investigated as part of a prospective follow-up study, where 6-year-old children and their families (n=1132) were followed to the age of 12-years (n=1126). The study design entailed both a cohort and case-control group. The incidence of headache and the association between headache and behavior were studied in another cohort, consisting of 11-year-old twins (n=5393), who were followed to the age of 17 (n=4159). The prevalence rates of headache increased during the follow-up, especially in boys whose mothers suffered from frequent headache. The incidence rates of frequent headache changed the most in girls between ages of 11 and 14. Early-onset migraine and tension-type headache were equal predictors of migraine at age 12. The age-related changes observed in pain localization, concurrent symptoms and triggers were considerable. Headache frequency was significantly associated with externalizing and internalizing problem behaviors and adaptive behaviors as rated by parents, but only with externalizing problem behaviors as rated by teachers. Headache both in children and adolescents is characterized by its changing nature. Its prevention and treatment should take familial, environmental and psychosocial aspects into account.

Innate immunity genes as determinants of resistance/susceptibility to human disease : studies in leukemia patients

La leuc��mie lymphoblastique aigu�� des cellules Pr��-B (B-ALL) reste le type de cancer le plus souvent diagnostiqu�� chez les enfants. Des ��tudes ont montr�� que des d��terminants g��n��tiques jouent un r��le important dans la susceptibilit��/r��sistance au d��veloppement de ce cancer. �� cet ��gard, les g��nes Killer-cell Immunoglobulin-like Receptor (KIR) sont d'une importance particuli��re. Ces g��nes sont fortement polymorphiques et codent pour des r��cepteurs qui contr��lent l���activit�� fonctionnelle des cellules Natural Killer (NK). Notre hypoth��se est que les g��nes activateurs des KIR s���associent avec la r��sistance inn��e pour d��velopper la B-ALL. Afin d'��valuer cette hypoth��se, nous avons entrepris une ��tude de cas-contr��les chez des enfants canadiens-fran��ais dans laquelle nous avons utilis�� l'ADN g��nomique de 100 patients atteints de B-ALL ainsi que l���ADN de 245 individus sains. La pr��sence ou l'absence de chaque g��ne KIR a ��t�� d��tect��e par PCR en utilisant des amorces de s��quences sp��cifiques. Nous avons trouv�� que la pr��sence des g��nes KIR activateurs est significativement diminu��e chez les enfants leuc��miques par rapport aux t��moins. En outre, le nombre de ces g��nes a aussi montr�� une association significative lin��aire avec la r��sistance au d��veloppement d���une B-ALL. Cela sugg��re des effets additifs de ces g��nes permettant de conf��rer une protection contre ce cancer. Ces r��sultats pourraient ��tre utiles afin de d��celer de fa��on pr��coce les enfants ayant un risque de d��velopper cette leuc��mie. Enfin, des strat��gies th��rapeutiques bas��es sur les r��cepteurs KIR pourraient ��tre envisag��es et s'av��rer utiles concernant le traitement de ce cancer chez les enfants.

Functional studies of the deubiquitinating enzymes USP19, USP4 and UCH-L1

El marcaje de prote��nas con ubiquitina, conocido como ubiquitinaci��n, cumple diferentes funciones que incluyen la regulaci��n de varios procesos celulares, tales como: la degradaci��n de prote��nas por medio del proteosoma, la reparaci��n del ADN, la se��alizaci��n mediada por receptores de membrana, y la endocitosis, entre otras (1). Las mol��culas de ubiquitina pueden ser removidas de sus sustratos gracias a la acci��n de un gran grupo de proteasas, llamadas enzimas deubiquitinizantes (DUBs) (2). Las DUBs son esenciales para la manutenci��n de la homeostasis de la ubiquitina y para la regulaci��n del estado de ubiquitinaci��n de diferentes sustratos. El gran n��mero y la diversidad de DUBs descritas refleja tanto su especificidad como su utilizaci��n para regular un amplio espectro de sustratos y v��as celulares. Aunque muchas DUBs han sido estudiadas a profundidad, actualmente se desconocen los sustratos y las funciones biol��gicas de la mayor��a de ellas. En este trabajo se investigaron las funciones de las DUBs: USP19, USP4 y UCH-L1. Utilizando varias t��cnicas de biolog��a molecular y celular se encontr�� que: i) USP19 es regulada por las ubiquitin ligasas SIAH1 y SIAH2 ii) USP19 es importante para regular HIF-1��, un factor de transcripci��n clave en la respuesta celular a hipoxia, iii) USP4 interact��a con el proteosoma, iv) La quimera mCherry-UCH-L1 reproduce parcialmente los fenotipos que nuestro grupo ha descrito previamente al usar otros constructos de la misma enzima, y v) UCH-L1 promueve la internalizaci��n de la bacteria Yersinia pseudotuberculosis.

'Moving On' and Transitional Bridges : Studies on migration, violence and wellbeing in encounters with Somali-born women and the maternity health care in Sweden

During the latest decade Somali-born women with experiences of long-lasting war followed by migration have increasingly encountered Swedish maternity care, where antenatal care midwives are assigned to ask questions about exposure to violence. The overall aim in this thesis was to gain deeper understanding of Somali-born women���s wellbeing and needs during the parallel transitions of migration to Sweden and childbearing, focusing on maternity healthcare encounters and violence. Data were obtained from medical records (paper I), qualitative interviews with Somali-born women (II, III) and Swedish antenatal care midwives (IV). Descriptive statistics and thematic analysis were used. Compared to pregnancies of Swedish-born women, Somali-born women���s pregnancies demonstrated later booking and less visits to antenatal care, more maternal morbidity but less psychiatric treatment, less medical pain relief during delivery and more emergency caesarean sections and small-for-gestational-age infants (I). Political violence with broken societal structures before migration contributed to up-rootedness, limited healthcare and absent state-based support to women subjected to violence, which reinforced reliance on social networks, own endurance and faith in Somalia (II). After migration, sources of wellbeing were a pragmatic ���moving-on��� approach including faith and motherhood, combined with social coherence. Lawful rights for women were appreciated but could concurrently risk creating power tensions in partner relationships. Generally, the Somali-born women associated the midwife more with providing medical care than with overall wellbeing or concerns about violence, but new societal resources were parallel incorporated with known resources (III). Midwives strived for woman-centered approaches beyond ethnicity and culture in care encounters, with language, social gaps and divergent views on violence as potential barriers in violence inquiry. Somali-born women���s strength and contentment were highlighted, and ongoing violence seldom encountered according to the midwives experiences (IV). Pragmatism including ���moving on��� combined with support from family and social networks, indicate capability to cope with violence and migration-related stress. However, this must be balanced against potential unspoken needs at individual level in care encounters.With trustful relationships, optimized interaction and networking with local Somali communities and across professions, the antenatal midwife can have a ���bridging-function��� in balancing between dual societies and contribute to healthy transitions in the new society.

The relationship between obesity, low back pain, and lumbar disc degeneration when genetics and the environment are considered: a systematic review of twin studies

BACKGROUND CONTEXT: The relationships between obesity and low back pain (LBP) and lumbar disc degeneration (LDD) remain unclear. It is possible that familial factors, including genetics and early environment, affect these relationships.PURPOSE: To investigate the relationship between obesity-related measures (eg, weight, body mass index [BMI]) and LBP and LDD using twin studies, where the effect of genetics and early environment can be controlled.STUDY DESIGN: A systematic review with meta-analysis.METHODS: MEDLINE, CINAHL, Scopus, Web of Science, and EMBASE databases were searched from the earliest records to August 2014. All cross-sectional and longitudinal observational twin studies identified by the search strategy were considered for inclusion. Two investigators independently assessed the eligibility, conducted the quality assessment, and extracted the data. Metaanalyses (fixed or random effects, as appropriate) were used to pool studies'estimates of association.RESULTS: In total, 11 articles met the inclusion criteria. Five studies were included in the LBP analysis and seven in the LDD analysis. For the LBP analysis, pooling of the five studies showed that the risk of having LBP for individuals with the highest levels of BMI or weight was almost twice that of people with a lower BMI (odds ratio [OR] 1.8; 95% confidence interval [CI] 1.6-2.0; I-2 = 0%). A dose-response relationship was also identified. When genetics and the effects of a shared early environment were adjusted for using a within-pair twin case-control analysis, pooling of three studies showed a reduced but statistically positive association between obesity and prevalence of LBP (OR 1.5; 95% CI 1.1-2.1; I-2 = 0%). However, the association was further diminished and not significant (OR 1.4; 95% CI 0.8-2.3; I-2 = 0%) when pooling included two studies on monozygotic twin pairs only. Seven studies met the inclusion criteria for LDD. When familial factors were not controlled for, body weight was positively associated with LDD in all five cross-sectional studies. Only two cross-sectional studies investigated the relationship between obesity-related measures and LDD accounting for familial factors, and the results were conflicting. One longitudinal study in LBP and three longitudinal studies in LDD found no increase in risk in obese individuals, whether or not familial factors were controlled for.CONCLUSIONS: Findings from this review suggest that genetics and early environment are possible mechanisms underlying the relationship between obesity and LBP; however, a direct causal link between these conditions appears to be weak. Further longitudinal studies using the twin design are needed to better understand the complex mechanisms underlying the associations between obesity, LBP, and LDD.