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Loneliness and social isolation have negative health consequences and are associated with depression. Personality characteristics are important when studying persons at risk for loneliness and social isolation. The objective of this study was to clarify the association between personality factors, loneliness and social network, taking into account diagnosis of depression, partner status and gender.
Cross-sectional data of an ongoing prospective cohort study, the Netherlands Study of Depression in Older Persons (NESDO), were used.
Setting and participants:
474 participants were recruited from mental health care institutions and general practitioners in five different regions in the Netherlands.
NEO-Five Factor Inventory (NEO-FFI) personality factors and loneliness and social network were measured as well as possible confounders. Multinominal logistic regression analyses were performed to analyse the associations between NEO-FFI factors and loneliness and social network. Interaction terms were investigated for depression, partner status and gender.
Higher neuroticism and lower extraversion in women and lower agreeableness in both men and women were associated with loneliness but not with social network size irrespective of the presence of depression. In the non-depressed group only, lower openness was associated with loneliness. Interaction terms with partner status were not significant.
Personality factors are associated with loneliness especially in women. In men lower agreeableness contributes to higher loneliness. In non-depressed men and women, lower openness is associated with loneliness. Personality factors are not associated with social network size.
We assessed whether paternal demographic, anthropometric and clinical factors influence the risk of an infant being born large-for-gestational-age (LGA). We examined the data on 3659 fathers of term offspring (including 662 LGA infants) born to primiparous women from Screening for Pregnancy Endpoints (SCOPE). LGA was defined as birth weight >90th centile as per INTERGROWTH 21st standards, with reference group being infants ⩽90th centile. Associations between paternal factors and likelihood of an LGA infant were examined using univariable and multivariable models. Men who fathered LGA babies were 180 g heavier at birth (P<0.001) and were more likely to have been born macrosomic (P<0.001) than those whose infants were not LGA. Fathers of LGA infants were 2.1 cm taller (P<0.001), 2.8 kg heavier (P<0.001) and had similar body mass index (BMI). In multivariable models, increasing paternal birth weight and height were independently associated with greater odds of having an LGA infant, irrespective of maternal factors. One unit increase in paternal BMI was associated with 2.9% greater odds of having an LGA boy but not girl; however, this association disappeared after adjustment for maternal BMI. There were no associations between paternal demographic factors or clinical history and infant LGA. In conclusion, fathers who were heavier at birth and were taller were more likely to have an LGA infant, but maternal BMI had a dominant influence on LGA.
Psychiatric patients are at increased risk to become victim of violence. It remains unknown whether subjects of the general population with mental disorders are at risk of victimisation as well. In addition, it remains unclear whether the risk of victimisation differs across specific disorders. This study aimed to determine whether a broad range of mood, anxiety and substance use disorders at baseline predict adult violent (physical and/or sexual) and psychological victimisation at 3-year follow-up, also after adjustment for childhood trauma. Furthermore, this study aimed to examine whether specific types of childhood trauma predict violent and psychological victimisation at follow-up, after adjustment for mental disorder. Finally, this study aimed to examine whether the co-occurrence of childhood trauma and any baseline mental disorder leads to an incrementally increased risk of future victimisation.
Data were derived from the first two waves of the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2): a psychiatric epidemiological cohort study among a nationally representative adult population. Mental disorders were assessed using the Composite International Diagnostic Interview version 3.0. Longitudinal associations between 12 mental disorders at baseline and violent and psychological victimisation at 3-year follow-up (n = 5303) were studied using logistic regression analyses, with adjustment for sociodemographic characteristics and childhood trauma. Furthermore, the moderating effect of childhood trauma on these associations was examined.
Associations with victimisation varied considerably across specific mental disorders. Only alcohol dependence predicted both violent and psychological victimisation after adjustment for sociodemographic characteristics and childhood trauma. Depression, panic disorder, social phobia, generalised anxiety disorder and alcohol dependence predicted subsequent psychological victimisation in the fully adjusted models. All types of childhood trauma independently predicted violent and psychological victimisation after adjustment for any mental disorder. The presence of any childhood trauma moderated the association between any anxiety disorder and psychological victimisation, whereas no interaction between mental disorder and childhood trauma on violent victimisation existed.
The current study shows that members of the general population with mental disorders are at increased risk of future victimisation. However, the associations with violent and psychological victimisation vary considerably across specific disorders. Clinicians should be aware of the increased risk of violent and psychological victimisation in individuals with these mental disorders – especially those with alcohol dependence – and individuals with a history of childhood trauma. Violence prevention programmes should be developed for people at risk. These programmes should not only address violent victimisation, but also psychological victimisation.
Growth rate is a major component of feed efficiency when estimating residual feed intake (RFI). Quantile regression (QR) methodology can be used to identify animals with different growth trajectories. The objective of this study was to evaluate the use of QR to identify phenotypic and genetic differences in pigs selected for low RFI. Using performance data on 750 Yorkshire pigs selected for low RFI, individual average daily gain (ADG), average daily feed intake (ADFI), RFI and Gompertz growth curve parameters (asymptotic weight (a), inflection point (b) and decay parameter (c)) were estimated for each pig. Using QR methodology, three Gompertz growth curves were estimated for the whole population for three quantiles (0.1, 0.5 and 0.9) of the BW data. Each animal was classified into one of the quantile regression groups (QRG) based on their overall Euclidian distance between each observed and estimated BW from the quantile growth curves. These three curves were also estimated using only part of the data (generations −1 to 3, and −1 to 4) in order to evaluate the agreement classification rate of animals from later generations into QRGs. We evaluated the effect of QRG on growth parameters and performance traits. Genetic parameters were estimated for these traits, as well as for QRG. In addition, genetic trends for each QRG were estimated. Three distinct growth curves were observed for animals classified into either quantiles 0.1 (QRG0.1), 0.5 (QRG0.5) or 0.9 (QRG0.9). When only part of the data was used to estimate quantile growth curves, all animals from QRG0.1 were correctly classified in their group. Animals in QRG0.1 had significantly lower ADFI, ADG and RFI, and greater a, b and c than animals in the other groups. Quantile regression groups analysed as a trait was highly heritable (0.41) and had high (0.8) and moderate (0.46) genetic correlations with ADG and RFI, respectively. Selection for reduced RFI increased the number of animals classified as QRG0.1 in the population. Overall, downward genetic trends were observed for all traits as a function of selection for reduced RFI. However, QRG0.1 was the only group that had a positive genetic trend for ADG. Altogether, these results indicate that selection for reduced RFI changes the shape of growth curves in Yorkshire in pigs, and that QR methodology was able to identify animals having different genetic potential for feed efficiency, bringing a new opportunity to improve selection for reduced RFI.
Two highly pathogenic avian influenza (HPAI) outbreaks have affected commercial egg production flocks in the American continent in recent years; a H7N3 outbreak in Mexico in 2012 that caused 70% to 85% mortality and a H5N2 outbreak in the United States in 2015 with over 99% mortality. Blood samples were obtained from survivors of each outbreak and from age and genetics matched non-affected controls. A total of 485 individuals (survivors and controls) were genotyped with a 600 k single nucleotide polymorphism (SNP) array to detect genomic regions that influenced the outcome of highly pathogenic influenza infection in the two outbreaks. A total of 420458 high quality, segregating SNPs were identified across all samples. Genetic differences between survivors and controls were analyzed using a logistic model, mixed models and a Bayesian variable selection approach. Several genomic regions potentially associated with resistance to HPAI were identified, after performing multidimensional scaling and adjustment for multiple testing. Analysis conducted within each outbreak identified different genomic regions for resistance to the two virus strains. The strongest signals for the Iowa H5N2 survivor samples were detected on chromosomes 1, 7, 9 and 15. Positional candidate genes were mainly coding for plasma membrane proteins with receptor activity and were also involved in immune response. Three regions with the strongest signal for the Mexico H7N3 samples were located on chromosomes 1 and 5. Neuronal cell surface, signal transduction and immune response proteins coding genes were located in the close proximity of these regions.
To investigate whether the safety culture of a hospital unit is associated with the ability to improve.
Qualitative investigation of safety culture on hospital units following a before-and-after trial on hand hygiene.
VU University Medical Center, a tertiary-care hospital in the Netherlands.
With support from hospital management, we implemented a hospital-wide program to improve compliance. Over 2 years, compliance was measured through direct observation, twice before, and 4 times after interventions. We analyzed changes in compliance from baseline, and selected units to evaluate safety culture using a positive deviance approach: the hospital unit with the highest hand hygiene compliance and 2 units that showed significant improvement (21% and 16%, respectively) were selected as high performing. Another 2 units showed no improvement and were selected as low performing. A blinded, independent observer conducted interviews with unit management, physicians, and nurses, based on the Hospital Survey on Patient Safety Culture. Safety culture was categorized as pathological (lowest level), reactive, bureaucratic, proactive, or generative (highest level).
Overall, 3 units showed a proactive or generative safety culture and 2 units had bureaucratic or pathological safety cultures. When comparing compliance and interview results, high-performing units showed high levels of safety culture, while low-performing units showed low levels of safety culture.
Safety culture is associated with the ability to improve hand hygiene. Interventions may not be effective when applied in units with low levels of safety culture. Although additional research is needed to corroborate our findings, the safety culture on a unit can benefit from enhancement strategies such as team-building exercises. Strengthening the safety culture before implementing interventions could aid improvement and prevent nonproductive interventions.
Several authors claimed that expression of suicidal ideation is one of the most important predictors of completed suicide. However, the strength of the association between suicidal ideation and subsequent completed suicide has not been firmly established in different populations. Furthermore, the absolute suicide risk after expression of suicidal ideation is unknown. In this meta-analysis, we examined whether the expression of suicidal ideation predicted subsequent completed suicide in various populations, including both psychiatric and non-psychiatric populations.
A meta-analysis of cohort and case–control studies that assessed suicidal ideation as determinant for completed suicide in adults. Two independent reviewers screened 5726 articles for eligibility and extracted data of the 81 included studies. Pooled risk ratios were estimated in a random effects model stratified for different populations. Meta-regression analysis was used to determine suicide risk during the first year of follow-up.
The risk for completed suicide was clearly higher in people who had expressed suicidal ideation compared with people who had not, with substantial variation between the different populations: risk ratio ranging from 2.35 (95% confidence interval (CI) 1.43–3.87) in affective disorder populations to 8.00 (95% CI 5.46–11.7) in non-psychiatric populations. In contrast, the suicide risk after expression of suicidal ideation in the first year of follow-up was higher in psychiatric patients (risk 1.40%, 95% CI 0.74–2.64) than in non-psychiatric participants (risk 0.23%, 95% CI 0.10–0.54). Past suicide attempt-adjusted risk ratios were not pooled due to large underreporting.
Assessment of suicidal ideation is of priority in psychiatric patients. Expression of suicidal ideation in psychiatric patients should prompt secondary prevention strategies to reduce their substantial increased risk of suicide.
Patients with a severe mental illness (SMI) are more likely to experience
victimisation than the general population.
To examine the prevalence of victimisation in people with SMI, and the
relationship between symptoms, treatment facility and indices of
substance use/misuse and perpetration, in comparison with the general
Victimisation was assessed among both randomly selected patients with SMI
(n = 216) and the general population
Compared with the general population, a high prevalence of violent
victimisation was found among the SMI group (22.7% v.
8.5%). Compared with out-patients and patients in a sheltered housing
facility, in-patients were most often victimised (violent crimes: 35.3%;
property crimes: 47.1%). Risk factors among the SMI group for violent
victimisation included young age and disorganisation, and risk factors
for property crimes included being an in-patient, disorganisation and
cannabis use. The SMI group were most often assaulted by someone they
Caregivers should be aware that patients with SMI are at risk of violent
victimisation. Interventions need to be developed to reduce this
The effect of prenatal distress on the risk of a small for gestational age (SGA) infant is uncertain. We have addressed the influences of prenatal stress, anxiety and depression on the risk of SGA. We also examined the effects of infant sex and timing of distress during pregnancy on any observed associations.
The study population comprised 5606 healthy nulliparous pregnant women who participated in the international prospective Screening for Obstetric and Pregnancy Endpoints (SCOPE) study. Women completed the Perceived Stress Scale (PSS), the short form of the Spielberger State–Trait Anxiety Inventory (STAI) and the Edinburgh Postnatal Depression Scale (EPDS) at 15 ± 1 and 20 ± 1 weeks' gestation. SGA was defined as birthweight below the 10th customized percentile. Logistic regression was used for data analysis, adjusting for several potential confounders such as maternal age, body mass index (BMI), smoking, socio-economic status and physical exercise.
The risk of SGA was increased in relation to mild [adjusted odds ratio (aOR) 1.35, 95% confidence interval (CI) 1.07–1.71], moderate (aOR 1.26, 95% CI 1.06–1.49), high (aOR 1.45, 95% CI 1.08–1.95) and very high stress scores (aOR 1.56, 95% CI 1.03–2.37); very high anxiety score (aOR 1.45, 95% CI 1.13–1.86); and very high depression score (aOR 1.14, 95% CI 1.05–1.24) at 20 ± 1 weeks' gestation. Sensitivity analyses showed that very high anxiety and very high depression increases the risk of SGA in males but not in females whereas stress increases the risk of SGA in both males and females.
These findings suggest that prenatal stress, anxiety and depression measured at 20 weeks' gestation increase the risk of SGA. The effects of maternal anxiety and depression on SGA were strongest in male infants.
Endothelial dysfunction (ED), low-grade inflammation (LGI) and oxidative stress (OxS) may be involved in the pathobiology of depression. Previous studies on the association of these processes in depression have yielded contradictory results. We therefore investigated comprehensively, in a population-based cohort study, the association between ED, LGI and OxS on the one hand and depressive symptoms on the other.
We used data from the Hoorn Study and determined biomarkers of ED [flow-mediated dilatation (FMD), von Willebrand factor, soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1, soluble thrombomodulin and soluble endothelial selectin], LGI [C-reactive protein, tumour necrosis factor-α, interleukin 6, interleukin 8, serum amyloid A, myeloperoxidase (MPO) and sICAM-1] and OxS (oxidized low density lipoprotein and MPO). Depressive symptoms were quantified by the Center for Epidemiologic Studies Depression Scale (CES-D) questionnaire (n = 493; age 68 years; 49.9% female). Regression analyses were performed with the use of biomarker Z scores. Adjustments were made for age, sex and glucose metabolism status (cohort stratification variables) and prior cardiovascular disease, hypertension, waist-to-hip ratio, cholesterol levels, education level, physical activity, dietary habits, and the use of antihypertensive and/or lipid-lowering medication and/or metformin (potential confounders).
After adjustment for age, sex and glucose metabolism status, one standard deviation increase in the ED Z score was associated with a 1.9 [95% confidence interval (CI) 0.7–3.1] higher CES-D score. Additional adjustments did not materially change this result. LGI and OxS were not associated with the CES-D score.
ED, as quantified by an array of circulating biomarkers and FMD, was independently associated with depressive symptoms. This study supports the hypothesis that ED plays an important role in the pathobiology of depression.
Accurate food and nutrient intake assessment is essential for investigating diet–disease relationships. In the present study, food and nutrient intake assessment among European adolescents using 24 h recalls (mean of two recalls) and a FFQ (separately and the combination of both) were evaluated using concentration biomarkers. Biomarkers included were vitamin C, β-carotene, DHA+EPA, vitamin B12 (cobalamin and holo-transcobalamin) and folate (erythrocyte folate and plasma folate). For the evaluation of the food intake assessment 390 adolescents were included, while 697 were included for the nutrient intake assessment evaluation. Spearman rank and Pearson correlations, and validity coefficients, which are correlations between intake estimated and habitual true intake, were calculated. Correlations were higher between frequency of food consumption (from the FFQ) and concentration biomarkers than between mean food intake (from the recalls) and concentration biomarkers, especially for DHA+EPA (r 0·35 v. r 0·27). Most correlations were higher among girls than boys. For boys, the highest validity coefficients were found for frequency of fruit consumption (0·88) and for DHA+EPA biomarker (0·71). In girls, the highest validity coefficients were found for fruit consumption frequency (0·76), vegetable consumption frequency (0·74), mean fruit intake (0·90) and DHA+EPA biomarker (0·69). After exclusion of underreporters, correlations slightly improved. Correlations between usual food intakes, adjusted for food consumption frequency, and concentration biomarkers were higher than correlations between mean food intakes and concentration biomarkers. In conclusion, two non-consecutive 24 h recalls in combination with a FFQ seem to be appropriate to rank subjects according to their usual food intake.
The relationship between cannabis use and cognitive functioning in patients with psychosis has yielded contradictory findings. In individuals at genetic high risk for psychosis, information is sparse. The aim of this study was to assess the association between recency and frequency of cannabis use and cognitive functioning in patients with psychosis and their unaffected siblings.
We conducted a cross-sectional study in 956 patients with non-affective psychosis, 953 unaffected siblings, and 554 control subjects. Participants completed a cognitive test battery including assessments of verbal learning, set shifting, sustained attention, processing speed, working memory, acquired knowledge, reasoning and problem solving and social cognition. Cannabis use was assessed by urinalysis and by the Composite International Diagnostic Interview. Using random-effect regression models the main effects of cannabis (recency and frequency) and the interaction with status (patient, sibling, control) on cognitive functioning were assessed.
Current cannabis use was associated with poorer performance on immediate verbal learning, processing speed and working memory (Cohen's d −0.20 to −0.33, p<0.005). Lifetime cannabis use was associated with better performance on acquired knowledge, facial affect recognition and face identity recognition (Cohen's d+0.17 to +0.33, p<0.005). There was no significant interaction between cannabis and status on cognitive functioning.
Lifetime cannabis-using individuals might constitute a subgroup with a higher cognitive potential. The residual effects of cannabis may impair short-term memory and processing speed.
Residual feed intake (RFI), defined as the difference between observed and expected feed intake based on growth and backfat, has been used to investigate genetic variation in feed efficiency in cattle, poultry and pigs. However, little is known about the biological basis of differences in RFI in pigs. To this end, the objective of this study was to evaluate the fifth generation of a line of pigs selected for reduced RFI against a randomly selected Control line for performance, carcass and chemical carcass composition and overall efficiency. Here, emphasis was on the early grower phase. A total of 100 barrows, 50 from each line, were paired by age and weight (22.6 ± 3.9 kg) and randomly assigned to one of four feeding treatments in 11 replicates: ad libitum (Ad), 75% of Ad (Ad75), 55% of Ad (Ad55) and weight stasis (WS), which involved weekly adjustments in intake to keep body weight (BW) constant for each pig. Pigs were individually penned (group housing was used for selection) and were on treatment for 6 weeks. Initial BW did not significantly differ between the lines (P > 0.17). Under Ad feeding, the low RFI pigs consumed 8% less feed compared with Control line pigs (P < 0.06), had less carcass fat (P < 0.05), but with no significant difference in growth rate (P > 0.85). Under restricted feeding, low RFI pigs under the Ad75 treatment had a greater rate of gain while consuming the same amount of feed as Control pigs. Despite the greater gain, no significant line differences in carcass composition or carcass traits were observed. For the WS treatment, low RFI pigs had similar BW (P > 0.37) with no significant difference in feed consumption (P > 0.32). Overall, selection for reduced RFI has decreased feed intake, with limited differences in growth rate but reduced carcass fat, as seen under Ad feeding. Collectively, results indicate that the effects of selection for low RFI are evident during the early grower stage, which allows for greater savings to the producer.
To gain insight into pertussis disease dynamics, we studied age-specific long-term periodicity and seasonality of pertussis in The Netherlands. Hierarchical time-series models were used to analyse the monthly reported pertussis incidence in January 1996–June 2006 by age group. The incidence of pertussis showed a slightly increasing long-term trend with highest incidence rates seen in 1996, 1999, 2001 and 2004. For all age groups the annual peak incidence was found in August, except for the 13–18 years age group where the peak occurred in November. Monthly trends in adults showed high correlation with trends in age groups 0–4 years (0·94) and 5–12 years (0·92). We found no evidence for a relationship between annual rises in pertussis and the opening of schools. Concurrent annual fluctuations of pertussis incidence in adults and infants suggest frequent transmission within and between these age groups. Studying trends offers insight into transmission dynamics and may facilitate decisions on future vaccination strategies.
In an extended twin study we estimated the heritability of fasting HbA1c and blood glucose levels. Blood glucose was assessed in different settings (at home and in the clinic). We tested whether the genetic factors influencing fasting blood glucose levels overlapped with those influencing HbA1c and whether the same genetic factors were expressed across different settings. Fasting blood glucose was measured at home and during two visits to the clinic in 77 healthy families with same-sex twins and siblings, aged 20 to 45 years. HbA1c was measured during the first clinic visit. A 4-variate genetic structural equation model was used that estimated the heritability of each trait and the genetic correlations among traits. Heritability explained 75% of the variance in HbA1c. The heritability of fasting blood glucose was estimated at 66% at home and lower in the clinic (57% and 38%). Fasting blood glucose levels were significantly correlated across settings (0.34 < r < 0.54), mostly due to a common set of genes that explained between 53% and 95% of these correlations. Correlations between HbA1c and fasting blood glucoses were low (0.11 < r < 0.23) and genetic factors influencing HbA1c and fasting glucose were uncorrelated. These results suggest that in healthy adults the genes influencing HbA1c and fasting blood glucose reflect different aspects of the glucose metabolism. As a consequence these two glycemic parameters can not be used interchangeably in diagnostic procedures or in studies attempting to find genes for diabetes. Both contribute unique (genetic) information.
Effectiveness of marker-assisted selection (MAS) and quantitative trait locus (QTL) mapping using population-wide linkage disequilibrium (LD) between markers and QTLs depends on the extent of LD and how it declines with distance between markers and QTLs in a population. Marker–QTL LD can be predicted from LD between markers. Our previous work evaluated LD measures between multi-allelic markers as predictors of usable LD of multi-allelic markers with QTLs. Since single nucleotide polymorphisms (SNPs) are the current marker of choice for high-density genotyping and LD-mapping of QTLs, the objective of this study was to use LD between multi-allelic markers to predict LD among biallelic SNPs or between SNPs and QTLs. Observable LD between multi-allelic markers was evaluated using nine measures. These included two pooled and standardized measures of LD between pairs of alleles at two markers based on Lewontin's LD measure, two pooled measures of squared correlations between alleles, one standardized measure using Hardy–Weinberg heterozygosities, and four measures based on the chi-square statistic for testing for association between alleles at two loci. The standardized chi-square measure that best predicted usable LD between multi-allelic markers and QTLs, based on our previous work, overestimated usable SNP–SNP or SNP–QTL LD. Instead, three other measures were found to be good predictors of usable SNP–SNP or SNP–QTL LD when LD is generated by drift. Therefore, the LD measure between multi-allelic markers that is best for predicting usable LD in a population depends on the type of markers (i.e. multi-allelic or biallelic) that will eventually be used for QTL mapping or MAS.
Since the 1970’s, several developments have raised high expectations for the use of molecular genetic technology to enhance selection in livestock through application of marker-assisted selection (MAS). These include the discovery of technologies that enabled identification and genotyping of large numbers of genetic markers, and research and statistical methods that demonstrated how these technologies can be used to identify genomic regions that control quantitative traits and how the resulting quantitative trait loci (QTL) can be used in MAS. Yet, to date, the application of MAS in livestock has been limited (see e.g. review in Dekkers 2004). Recent further advances in technology, including genome sequencing and the associated discovery and identification of large numbers of single nucleotide polymorphisms (SNPs) that can be used as genetic markers, combined with the development of high-throughput SNP genotyping that allows the genotyping of large numbers of individuals for large numbers of SNPs at substantially reduced costs, have however stimulated a renewed interest in the large-scale application of MAS in livestock.
The combination of the collecting power of an ELT with an ultra-stable high resolution spectrograph opens up the possibility to measure for the first time directly the dynamical effect of the acceleration of the Universe. CODEX will also provide unique opportunities for advance in many other branches of astrophysics. The CODEX design is based on an array of several identical spectrographs. It is highly modular and can be easily adapted to a large range of sky apertures and telescope diameters. CODEX is designed to work as a seeing limited instrument. The requirements for the telescope are moderate and clearly identified.
Effectiveness of marker-assisted selection (MAS) and quantitative trait loci (QTL) mapping using population-wide linkage disequilibrium (LD) between markers and QTL depends on the extent of LD and how it declines with distance in a population. Because marker–QTL LD cannot be observed directly, the objective of this study was to evaluate alternative measures of observable LD between multi-allelic markers as predictors of usable LD of multi-allelic markers with presumed biallelic QTL. Observable LD between marker pairs was evaluated using eight existing measures and one new measure. These consisted of two pooled and standardized measures of LD between pairs of alleles at two markers based on Lewontin's LD measure, two pooled measures of squared correlations between alleles, one standardized measure using Hardy–Weinberg heterozygosities, and four measures based on the chi-square statistic for testing for association between alleles at two loci. In simulated populations with a range of LD generated by drift and a range of marker polymorphism, marker–marker LD measured by a standardized chi-square statistic (denoted χ2′) was found to be the best predictor of useable marker–QTL LD for a group of multi-allelic markers. Estimates of the level and decline of marker–marker LD with distance obtained from χ2′ were linearly and highly correlated with usable LD of those markers with QTL across population structures and marker polymorphism. Corresponding relationships were poorer for the other marker–marker LD measures. Therefore, when LD is generated by drift, χ2′ is recommended to quantify the amount and extent of usable LD in a population for QTL mapping and MAS based on multi-allelic markers.
Objectives: Health services research is a typical instance of applied research, meaning that its research findings should contribute to a more evidence-based health policy. A basic assumption for the usefulness of policy research is that it is of good scientific quality, but evaluation of health services research would be incomplete without an assessment of its societal relevance. However, there is no generally accepted framework in which criteria to assess societal relevance are defined.
Methods: In this study, we made an effort to specify criteria and indicators for policy relevance.
Results and Conclusions: In general, we concluded that it is important to define from the start of a research project, what kind of answers are being sought to the questions at hand, who the intended users of these answers will be, and how they can be reached. Furthermore, a productive dialogue between researchers and policy makers is indispensable for remaining in tune with policy thinking. In addition, we specified domains and a list of potential criteria for assessing policy relevance. For the purpose of quality assurance, these criteria have to be integrated into a quality improvement cycle. This means that the societal output of health services research should be related to the aims and missions at the level of projects, programs, and institutes. Furthermore, it is important that consensus is reached about (the weighting of) relevant indicators and that routines are developed for collecting information on these indicators.