Person: Madrid Valero, Juan José
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Disparity between central and peripheral refraction inheritance in twins
The last decades have witnessed a sudden increase in myopia incidence among youngsters that have been related to modern lifestyle along with the use of emerging technologies affecting visual exposure. Increasing exposures to known risk factors for myopia, such as time spent indoors, close-distance work, or low-light conditions are thought to be responsible for this public health issue. In most cases, development of myopia is secondary to a vitreous chamber enlargement, although the related mechanisms and the potential interaction between central and peripheral retinal area remain unclear. For a better understanding, we performed a classical twin study where objective refractive error along 70° of horizontal retinal arc was measured in 100 twin pairs of university students, 78% of which showed manifest myopia. We found the variance of shared environmental origin (range 0.34 to 0.67) explained most of the objective refractive error variance within central 42° of the retina (22° temporal to 19° nasal), whereas additive genetic variance (range 0.34 to 0.76) was predominant in the peripheral retinal areas measured. In this sample of millennial university students, with a large prevalence of myopia, environmental exposures were mostly responsible for inter-individual variation in the retinal horizontal area surrounding the macula, while their relative weight on phenotypic variance was gradually descending, and replaced by the variance of genetic origin, towards the retinal periphery.
Comunicaciones Orales.-Relación entre la calidad de sueño y el Índice de masa corporal
Impact of Genetic and Environmental Factors on Peripheral Refraction
Investigate genetic and environmental influences on refractive errors in monozygotic (MZ) and dizygotic (DZ) twin pairs. We assessed foveal and peripheral refractions in 54 MZ and 46 DZ twins, capturing three scans across the retina. The study focused on spherical equivalent (M) at the fovea (MLOS) and changes in midperipheral (δMmid-periphery), and peripheral (δMperiphery) defocus, along with nasal-temporal asymmetry (root mean squared error [RMSEASY]) and image shell contour (RMSEAVG). Genetic and environmental contributions were analyzed using structural equation models. No significant differences were observed between MZ and DZ twins for the examined variables. Intraclass correlations (ICC) indicated an important difference in genetic influence between MLOS, with the MZ twin pairs showing a higher correlation (0.83) than DZ (0.69) pairs, and δMperiphery, because the ICC for the MZ doubled (0.87) that of the DZ (0.42) pairs. Heritability estimates from the ACE model confirmed the large difference on genetic factors' influence on the variance for MLOS (0.13) and δMperiphery (0.77) change in refractive error. RMSEASY and RMSEAVG metrics showed significant genetic impact, particularly pronounced in the peripheral measurements, revealing high genetic control. The study delineates a marked environmental impact on central refractive errors, whereas genetic factors had a more significant influence on peripheral refractive variance and retinal image traits. Findings of the ACE model highlight the intricate genetic and environmental interplay in refractive error development, with a notable genetic dominance in peripheral vision characteristics. This suggests potential genetic targets for interventions in myopia management and emphasizes the need for personalized approaches based on genetic predispositions. Understanding the impact of genetics and environment on peripheral refraction is essential for deepening our fundamental knowledge of myopia and guiding the development of advanced myopia control strategies.
Factores genéticos y ambientales implicados en la calidad del sueño
Esta tesis doctoral partió con el objetivo de investigar las influencias genéticas y ambientales implicadas en la calidad de sueño. Para ello hace uso de diversas metodologías, incluyendo estudios epidemiológicos clásicos y análisis de genética cuantitativa, y tiene como recurso principal los registros de gemelos. Los datos disponibles sobre prevalencia en población española eran escasos y no actualizados. Por lo tanto, el estudio 1 se dirigió a conocer cómo es la calidad de sueño en la población española y qué efecto tienen factores como la edad, el sexo o el estatus menopáusico sobre la misma. Para ello, se utilizó una muestra representativa de la población de la Región de Murcia que puede ser comparable a la población española. Esta muestra estuvo formada por 2144 participantes en el RGM. En este estudio se comprobó que un alto porcentaje de la población en esta franja de edad presenta una pobre calidad de sueño. Además, se comprobó que las mujeres tenían casi el doble de probabilidad de presentar una pobre calidad de sueño respecto a los varones. La edad fue otro factor fundamental para la calidad de sueño. El estudio 2 trata de dar respuesta al porqué de las diferencias individuales en calidad de sueño. Por tanto, el objetivo principal de este estudio fue determinar las influencias genéticas y ambientales en población española y ver, si existían diferencias en la distribución de la varianza en función del sexo. Nuestros resultados mostraron que un porcentaje sustancial de la varianza en calidad de sueño se debe a factores genéticos, siendo el resto debido a factores ambientales no compartidos. Además, no se encontraron diferencias de sexo. El estudio 3 por su parte tuvo como objetivo estudiar la relación que existe entre la calidad de sueño y el índice de masa corporal (IMC). Estudios previos han demostrado que existe una estrecha relación entre la calidad de sueño y el IMC. Sin embargo, la direccionalidad y causalidad de esta relación es confusa. Se utilizó un diseño caso-control con gemelos, que nos permite altos niveles de control para posibles variables de confusión (incluyendo factores genéticos). Nuestros resultados confirman la estrecha relación que existe entre la calidad de sueño y el índice de masa corporal y además apuntan a una posible direccionalidad de la misma donde la calidad de sueño tiene un efecto significativo sobre el IMC, pero no al revés. El estudio 4 se centró en estudiar la relación existente entre diferentes características del sueño y el comportamiento antisocial en niños. Se utilizó una muestra del registro de gemelos de la Universidad Estatal de Michigan. Esta muestra estuvo formada por 1030 pares de gemelos con edades comprendidas entre 6 y 12 años. Las características de sueño y las dos dimensiones del comportamiento antisocial se evaluaron mediante el cuestionario CBCL. Se corroboró la fuerte asociación que existe entre el sueño y el comportamiento antisocial, encontrando puntuaciones muy superiores tanto en agresividad como en ruptura de las normas en aquellos niños que presentan problemas de sueño. Todos los fenotipos mostraron una fuerte influencia genética. Sin embargo, el patrón de relaciones encontrado fue diferente para cada una de las dimensiones del comportamiento antisocial y las distintas variables de sueño. Se encontró un importante solapamiento genético entre las medidas de sueño y agresividad, mientras que para la variable ruptura de las normas este solapamiento genético fue de menor magnitud y no significativo en la mayoría de los casos. Estos cuatro estudios aportan información novedosa sobre la calidad de sueño. Destacan la importancia de los factores genéticos a la hora de explicar su etiología e importancia para la salud general y el comportamiento
Inheritance of Refractive Error in Millennials
Over the last decades, the prevalence of myopia has suddenly increased, and at this rate, half of the world's population will be myopic by the year 2050. Contemporary behavioural and lifestyle circumstances, along with emergent technology, are thought to be responsible for this increase. Twin studies mostly reported a high heritability of refractive error across ethnicities. However, heritability is a population statistic and could vary as a result of changing environmental conditions. We studied the variance of refractive error in millennials with 100 twin pairs of university students in southeast Spain. The study population presented a high prevalence of myopia (77%). Statistical analysis showed the variance of refractive error in this group of young twins was mainly driven by the shared environment and, to a lesser extent, by additive genetic factors. We found an increase in myopia prevalence accompanied by a decrease in heritability in this sample of millennials in contrast with results from a previous generation group from the same ethnic origin.
Heritability of sleep quality in a middle-aged twin sample from Spain
Study objectives: Sleep quality is associated with health throughout the life span, which is particularly salient in middle-age and older adulthood. Sleep quality appears to be influenced by both genetic and environmental factors. However, there is still limited information about genetic influences on sleep quality in middle-aged adults, and particularly in those from certain geographical locations. We estimated the magnitude of genetic and environmental influences on sleep quality in a representative sample of middle-aged Spanish twins. Methods: The sample comprised 2150 individuals born between 1939 and 1966, who participate in the Murcia Twin Registry. In order to estimate the heritability of sleep quality variables we performed univariate analyses for the global score on the Pittsburgh sleep quality index and for each of its components. Results: We found moderate but significant heritability (34%) for sleep quality. The genetic variance of the components of the Pittsburgh index ranged from 30% to 45%, except for sleep efficiency for which no genetic influence could be detected. In summary, there was a moderate genetic influence on most dimensions of sleep quality in a sample of adult male and female twins. Shared environment influences were not found. Conclusions: This study adds new information regarding the underlying determinants of sleep quality by providing heritability estimates in a middle-aged population-based representative sample from a geographical location that has not been included in studies of this type previously. This could provide a reference point for future research regarding sleep research in middle-age.