Nature and nurture. Genetic and environmental factors on the relationship between back pain and sleep quality.

BACKGROUND: Chronic low back pain (LBP), neck pain (NP), and sleep quality (SQ) are genetically influenced. All three conditions frequently co-occur and shared genetic aetiology on a pairwise base has been reported. However, to our knowledge, no study has yet investigated if these three conditions are influenced by the same genetic and environmental factors and the extent and pattern of genetic overlap between them, hence the current research. METHODS: The sample included 2134 participants. Lifetime prevalence of NP and LBP were assessed through a dichotomous self-reported question derived from the Spanish National Health Survey. SQ was measured using the Pittsburgh Sleep Quality Index Questionnaire. A common pathway model with sleep quality and back pain as latent factors was fitted. RESULTS: Our results highlight that a latent back pain factor, including both NP and LBP, is explained by both genetic (41%) and environmental (59%) factors. There are also significant unique environmental factors for NP (33%) and LBP (37%) respectively. Yet, specific genetic factors were scant (9%) for NP and negligible for LBP (0%). Genetic and environmental factors affecting SQ only contribute with 3% and 5% of the variance, respectively, to the common latent back pain variable. CONCLUSIONS: NP and LBP share most of their genetic variance, while environmental effects show greater specificity for each of the back pain locations. Associations with SQ were of a limited magnitude. SIGNIFICANCE: Our results confirm a significant association between both chronic NP and LBP and sleep quality. Such relationship comprises both genetic and environmental factors, with a greater relative weight of the latter. A large part of the individual variance for chronic LBP and chronic NP can be accounted for by a latent common factor of 'back pain'. Genetic influences for LBP and NP were mainly shared. However, environmental influences were common for both problems and specific for each of them in similar magnitudes.

An Update of Twin Research in Spain: The Murcia Twin Registry.

The Murcia Twin Registry (MTR) is the only population-based registry in Spain. Created in 2006, the registry has been growing more than a decade to become one of the references for twin research in the Mediterranean region. The MTR database currently comprises 3545 adult participants born between 1940 and 1977. It also holds a recently launched satellite registry of university students (N = 204). Along five waves of data collection, the registry has gathered questionnaire and anthropometric data, as well as biological samples. The MTR keeps its main research focus on health and health-related behaviors from a public health perspective. This includes lifestyle, health promotion, quality of life or environmental conditions. Future short-term development points to the expansion of the biobank and the continuation of the collection of longitudinal data.

Is occupational or leisure physical activity associated with low back pain? Insights from a cross-sectional study of 1059 participants.

BACKGROUND: Low back pain is a highly prevalent and disabling musculoskeletal disorder. Physical activity is widely used as a prevention strategy for numerous musculoskeletal disorders; however, there is still conflicting evidence as to whether physical activity is a protective or risk factor for low back pain or whether activity levels differ between people with and without low back pain. OBJECTIVE: To investigate the association between low back pain and different types (occupational and leisure) and intensities (moderate and vigorous) of physical activity. METHODS: This is cross-sectional observational study. We included in this study a total of 1059 individuals recruited from a Spanish twin registry with data available on low back pain. OUTCOME: Self-reported leisure and occupational physical activity were the explanatory variables. The low back pain outcome used in this study was recurrent low back pain. RESULTS: Our results indicate that leisure physical activity is associated with a lower prevalence of recurrent low back pain. In contrast, occupational physical activity, such as carrying, lifting heavy weight while inclined, awkward postures (e.g. bending, twisting, squatting, and kneeling) are associated with a higher prevalence of recurrent low back pain. There was no statistically significant association between other occupational physical activities, such as sitting or standing, and low back pain. CONCLUSION: Leisure and occupational physical activity are likely to have an opposed impact on low back pain. While leisure physical activity appears to be protective, occupational physical activity appears to be harmful to low back pain. Future longitudinal studies should assist in formulating guidelines addressing specific types and intensity of physical activity aimed at effectively preventing low back pain.

El Registro de Gemelos de Murcia. Un recurso para la investigación sobre conductas relacionadas con la salud / The Murcia Twin Registry. A resource for research on health-related behaviour

Los diseños genéticamente informativos, y en particular los estudios de gemelos, constituyen la metodología más utilizada para analizar la contribución relativa de los factores genéticos y ambientales a la variabilidad interindividual. Básicamente, consisten en comparar el grado de similitud, con respecto a una característica o rasgo determinado, entre gemelos monocigóticos y dicigóticos. Además de la clásica estimación de heredabilidad, este tipo de registros permite una amplia variedad de análisis únicos por las características de la muestra. El Registro de Gemelos de Murcia es un registro de base poblacional centrado en el análisis de conductas relacionadas con la salud. Las prevalencias de problemas de salud observadas son comparables a las de otras muestras de referencia de ámbito regional y estatal, lo que avala su representatividad. En conjunto, sus características facilitan el desarrollo de diversas modalidades de investigación, además de diseños genéticamente informativos y la colaboración con distintas iniciativas y consorcios (AU)

Genetically informative designs and, in particular, twin studies, are the most widely used methodology to analyse the relative contribution of genetic and environmental factors to inter-individual variability. These studies basically compare the degree of phenotypical similarity between monozygotic and dizygotic twin pairs. In addition to the traditional estimate of heritability, this kind of registry enables a wide variety of analyses which are unique due to the characteristics of the sample. The Murcia Twin Registry is population-based and focused on the analysis of health-related behaviour. The observed prevalence of health problems is comparable to that of other regional and national reference samples, which guarantees its representativeness. Overall, the characteristics of the Registry facilitate developing various types of research as well as genetically informative designs, and collaboration with different initiatives and consortia (AU)

[The Murcia Twin Registry. A resource for research on health-related behaviour]. / El Registro de Gemelos de Murcia. Un recurso para la investigación sobre conductas relacionadas con la salud.

Genetically informative designs and, in particular, twin studies, are the most widely used methodology to analyse the relative contribution of genetic and environmental factors to inter-individual variability. These studies basically compare the degree of phenotypical similarity between monozygotic and dizygotic twin pairs. In addition to the traditional estimate of heritability, this kind of registry enables a wide variety of analyses which are unique due to the characteristics of the sample. The Murcia Twin Registry is population-based and focused on the analysis of health-related behaviour. The observed prevalence of health problems is comparable to that of other regional and national reference samples, which guarantees its representativeness. Overall, the characteristics of the Registry facilitate developing various types of research as well as genetically informative designs, and collaboration with different initiatives and consortia.

Does sedentary behavior increase the risk of low back pain? A population-based co-twin study of Spanish twins.

BACKGROUND: The relationship between sedentary lifestyle and low back pain (LBP) remains unclear and previous research has not accounted for genetic and early environmental factors. PURPOSE: Our aim was to investigate if sedentary behavior is associated with the lifetime prevalence of persistent LBP and the risk of developing persistent LBP, care-seeking due to LBP, and activity limiting LBP when genetics and early environmental factors are accounted for. STUDY DESIGN: Both cross-sectional and longitudinal designs with a within-pair twin case-control were implemented. PATIENT SAMPLE: There were 2,148 twins included in the cross-sectional analysis whereas 1,098 twins free of persistent LBP at baseline were included in the longitudinal analysis. OUTCOME MEASURES: Sedentary behavior was the explanatory variable. Lifetime prevalence of LBP was the outcome variable in the cross-sectional analysis. The incidence of persistent LBP, care-seeking due to LBP, and activity limiting LBP were the outcome variables for the longitudinal analysis. METHODS: This observational study was supported by a grant in 2012. No competing interests were declared. RESULTS: In the cross-sectional analysis, sedentary behavior was slightly associated with an increased prevalence of persistent LBP in females but not in males. This association was not apparent when genetics and early environmental factors were accounted for. We acknowledge that the small sample included in the co-twin analyses have yielded wide confidence intervals, and that caution should be exercised when interpreting and an association may not be ruled out. In the longitudinal analysis, sedentary behavior did not significantly increase the risk of persistent LBP, care-seeking due to LBP, or activity limiting LBP. CONCLUSIONS: Sedentary behavior is associated with concurrent LBP. However, this association is weak; it only appears in females and decreases when accounting for genetics. Future studies using a twin design with larger samples should be conducted to further test these findings.

Genetics and the environment affect the relationship between depression and low back pain: a co-twin control study of Spanish twins.

Although the co-occurrence of low back pain (LBP) and depression is common, the nature of this association remains unclear. We aimed to investigate whether symptoms of depression are associated with LBP after adjusting for various confounders, including genetics. We used cross-sectional data from 2148 twins from the Murcia Twin Registry, Spain. All twins answered questions about lifetime prevalence of LBP (outcome variable) and symptoms of depression, collected through two instruments, deriving 3 measures: (1) self-report feelings of depression and anxiety; (2) state depression, and (3) trait depression. First, associations were investigated using logistic regression analysis of the total sample. We performed subsequent matched within-pair twin case-control analyses with all complete twin pairs discordant for LBP regardless of zygosity, and separately for dizygotic and monozygotic pairs. This sequential analysis allows for more precise estimates of the relationship between variables, as in each step, the impact of early shared environment and genetics is further considered. Symptoms of depression and anxiety were associated with higher prevalence of LBP in the total sample analysis (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.31-2.05), and this relationship was stronger in the subsequent case-control analysis (OR, 1.74; 95% CI, 1.13-2.69) and dizygotic case-control analysis (OR, 2.39; 95% CI, 1.39-4.08) but disappeared when the analysis was conducted for monozygotic twins (OR, 0.92; 95% CI, 0.42-2.05). A similar pattern was found for state and trait depression. The depression-LBP relationship disappears when high levels of control for confounding factors are applied and seems to be driven by genetic or environmental factors that influence both conditions.

The Murcia Twin Registry: a population-based registry of adult multiples in Spain.

The Murcia Twin Registry (MTR) was created in 2006, under the auspices of the University of Murcia and the regional Health Authority, aiming to develop a research resource in Spain intended to stimulate current research and new investigation on the analysis of genetic factors related to health and health-related behaviors. The MTR development strategy was designed as a step-by-step process. Initially, it was focused on women's health but nowadays it includes males and opposite-sex twins. The database comprises 2,281 participants born between 1940 and 1966 in the region of Murcia, in Spain. There have been three waves of data collection and today the MTR databases include questionnaire and anthropometric data as well as biological samples. The current main areas of research interest are health and health-related behaviors, including lifestyle, health promotion, and quality of life. Future short-term development points to the completion of the biobank and continuing the collection of longitudinal data.

An initiative in Spain for the study of women's health: the Murcia Twin Registry.

The present article describes the initial steps taken in setting up a twin registry in Spain. The Murcia Twin Registry (MTR) will focus initially on perimenopausal women's health. It will be administered and managed by the University of Murcia and the Murcia Health Council and will start with a database of 452 pairs of female twins born between 1940 and 1965 in the region of Murcia, Spain. Once the MTR is established and has gained some experience, our goal is to expand the age range and include males and opposite-sex twins. The current main areas of research interest are menopause, preventive behaviors, lifestyle and health as well as quality of life.

Efectos moduladores de la personalidad y la valoración subjetiva en la respuesta autonómica ante una tarea de hablar en público en mujeres sanas / Modulating effects of personality and situational appraisal on the autonomic response to a public speaking task in healthy women

El objetivo de este estudio fue examinar en una muestra de 16 mujeres, el efecto los de rasgos de personalidad y la valoración subjetiva ante un estresor social de laboratorio (hablar en público) en la respuesta cardiovascular y electrodérmica. Se midieron las respuestas de conductancia de la piel, la frecuencia cardiaca (FC) y el volumen del pulso periférico (VPP) durante un periodo de descanso, preparación, tarea y recuperación ante un discurso académico. Los sujetos fueron clasificados según sus puntuaciones altas o bajas en el cuestionario de personalidad EPQ, el STAI y en las medidas subjetivas. Los sujetos mostraron un aumento de la activación fisiológica significativo durante las fases de preparación y ejecución del discurso, esta activación estuvo modulada por las variables de personalidad y la valoración subjetiva. Los sujetos más extrovertidos mostraron mayor frecuencia de respuestas electrodérmicas (RED) a lo largo de todo el registro. Los sujetos que percibieron la tarea como más difícil mostraron los valores más altos en frecuencia cardiaca. Por último, aquéllos que percibieron un mayor estrés y esfuerzo mostraron un porcentaje de cambio mayor en volumen de pulso. Estos resultados apoyan el uso de la tarea de hablar en público como un buen estresor de laboratorio y la importancia de la experiencia subjetiva y los rasgos de personalidad del individuo como variables que modulan dicha respuesta. (AU)

Anticipatory autonomic response to a public speaking task in women: the role of trait anxiety.

The aim of this research was to study anticipatory autonomic responses their relationship to trait anxiety. Twenty-three women prepared an evaluated speech (S-condition) and 22 women an evaluated essay (W-condition). Heart rate (HR), finger pulse volume (FPV) and skin conductance were recorded before, during and after preparation of the task and during task performance; state-anxiety was evaluated before and after the task. In the total sample, state-anxiety was higher in the S- than in W-condition and this anxiety increase was accompanied by FPV reductions. However, when the sample was split according to trait anxiety scores, HR during preparation and increases of state-anxiety were greater in S- than W-condition in only in high-anxious women. Results suggest that specificity of anticipatory HR response to a public speaking task in women is moderated by cognitive anxiety.