Accessible and readily utilized software, tables and approximation formulae have been developed to estimate power and sample size for studies of time to event (survival times) when the survival times are assumed to be exponential. These methods can markedly misestimate power when the distribution is Weibull and not exponential. The Weibull distribution with increasing hazard is common in aging research, especially when the whole life span of the subjects is of interest.
The exceptional longevity of centenarians is due in part to inherited genetic factors, as deduced from data that show that first degree relatives of centenarians live longer and have reduced overall mortality. In recent years, a number of groups have performed genetic association studies on long-living individuals (LLI) and young controls to identify alleles that are either positively or negatively selected in the centenarian population as consequence of a demographic pressure. Many of the reported studies have shown genetic loci associated with longevity.
In the Georgia Centenarian Study (Poon et al., Exceptional Longevity, 2006), centenarian cases and young controls are classified according to three categories (age, ethnic origin, and single nucleotide polymorphisms [SNPs] of candidate longevity genes), where each factor has two possible levels. Here we provide methodologies to determine the minimum sample size needed to detect dependence in 2 x 2 x 2 tables based on Fisher's exact test evaluated exactly or by Markov chain Monte Carlo (MCMC), assuming only the case total L and the control total N are known.
BACKGROUND: It has been well established that both genes and non-shared environment contribute substantially to the underlying aetiology of major depressive disorder (MDD). A comprehensive overview of genetic research in MDD is presented. Method Papers were retrieved from PubMed up to December 2011, using many keywords including: depression, major depressive disorder, genetics, rare variants, gene-environment, whole genome, epigenetics, and specific candidate genes and variants. These were combined in a variety of permutations.
During the past two decades, research concerned with the aetiology of psychopathology has generally progressed along two separate paths: investigations that have characterised the roles played by environmental determinants such as childhood adversity in the development of psychopathology, and those that have focused on neurobiological processes involving genetic and intracellular pathways.
BACKGROUND: While families headed by same-sex couples have achieved greater public visibility in recent years, there are still many challenges for these families in dealing with legal and community contexts that are not supportive of same-sex relationships. The Work, Love, Play study is a large longitudinal study of same-sex parents. It aims to investigate many facets of family life among this sample and examine how they change over time.
BACKGROUND: The aim of this study was to identify romantic relationship characteristics, emotional and personality aspects and social adjustment in subjects with pathological jealousy (PJ) and to compare them to control group. METHODS: The participants, 32 individuals with PJ and 31 healthy volunteers completed measures of jealousy intensity, attachment type, love and relationship styles, personality, impulsivity, aggressiveness and social adjustment. Socio-demographic profiles were also obtained.
Twin Research: The Official Journal of the International Society for Twin Studies
Twin research offers the greatest power for the genetic analysis of complex multifactorial traits and diseases in humans. Modern twin analyses extend beyond the classical twin study for estimating the heritability of a trait. The human genome project can fulfil its promises only after functional characterisation of single genes in the context of genetic background and environment. Twin research can make a major contribution in that regard. Twin research is greatly facilitated by the willingness, motivation, cooperation, and generosity of the participants and their families.
BACKGROUND: Recruiting to randomized controlled trials is fraught with challenges; with less than one third recruiting to their original target. In preparation for a trial evaluating the effectiveness of a blood test to screen for lung cancer (the ECLS trial), we conducted a qualitative study to explore the potential barriers and facilitators that would impact recruitment. METHODS: Thirty two people recruited from community settings took part in four focus groups in Glasgow and Dundee (UK). Thematic analysis was used to code the data and develop themes.
The analysis of data from matched pairs binary experiments, often performed with McNemar's test, presents a unique experimental design challenge in dealing with the effect of the discordance probability, p. Most approaches for determining size and power use point estimates or maximization, but this fails to account for the considerable variability across values of the nuisance parameter that occur for all common tests.