Ole Birger Pedersen

Heritability of psoriasis in a large twin sample

Previous twin studies have shown greater concordance rates for psoriasis in MZ than in DZ twins, and heritability estimates between 66% and 90%. This supports a genetic influence on psoriasis, but also highlights the fact that genes are not the only explanation for the disease.

The new Scandinavian Donations and Transfusions database (SCANDAT2): a blood safety resource with added versatility

Risks of transfusion‐transmitted disease are currently at a record low in the developed world. Still, available methods for blood surveillance might not be sufficient to detect transmission of diseases with unknown etiologies or with very long incubation periods.

Association of Psoriasis With the Risk for Type 2 Diabetes Mellitus and Obesity

IMPORTANCE Psoriasis has been shown to be associated with overweight and type 2 diabetes mellitus. The genetic association is unclear. OBJECTIVE To examine the association among psoriasis, type 2 diabetes mellitus, and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) in twins. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional, population-based twin study included 34 781 Danish twins, 20 to 71 years of age. Data from a questionnaire on psoriasis was validated against hospital discharge diagnoses of psoriasis and compared with hospital discharge diagnoses of type 2 diabetes mellitus and self-reported BMI. Data were collected in the spring of 2002. Data were analyzed from January 1 to October 31, 2014. MAIN OUTCOMES AND MEASURES Crude and adjusted odds ratios (ORs) were calculated for psoriasis in relation to type 2 diabetes mellitus, increasing BMI, and obesity in the whole population of twins and in 449 psoriasis-discordant twins. Variance component analysis was used to measure genetic and nongenetic effects on the associations. RESULTS Among the 34 781 questionnaire respondents, 33 588 with complete data were included in the study (15 443 men [46.0%]; 18 145 women [54.0%]; mean [SD] age, 44.5 [7.6] years). After multivariable adjustment, a significant association was found between psoriasis and type 2 diabetes mellitus (odds ratio [OR], 1.53; 95% CI, 1.03-2.27; P = .04) and between psoriasis and increasing BMI (OR, 1.81; 95% CI, 1.28-2.55; P = .001 in individuals with a BMI>35.0). Among psoriasis-discordant twin pairs, the association between psoriasis and obesity was diluted in monozygotic twins (OR, 1.43; 95% CI, 0.50-4.07; P = .50) relative to dizygotic twins (OR, 2.13; 95% CI, 1.03-4.39; P = .04). Variance decomposition showed that additive genetic factors accounted for 68% (95% CI, 60%-75%) of the variance in the susceptibility to psoriasis, for 73% (95% CI, 58%-83%) of the variance in susceptibility to type 2 diabetes mellitus, and for 74% (95% CI, 72%-76%) of the variance in BMI. The genetic correlation between psoriasis and type 2 diabetes mellitus was 0.13 (-0.06 to 0.31; P = .17); between psoriasis and BMI, 0.12 (0.08 to 0.19; P < .001). The environmental correlation between psoriasis and type 2 diabetes mellitus was 0.10 (-0.71 to 0.17; P = .63); between psoriasis and BMI, -0.05 (-0.14 to 0.04; P = .44). CONCLUSIONS AND RELEVANCE This study determines the contribution of genetic and environmental factors to the interaction between obesity, type 2 diabetes mellitus, and psoriasis. Psoriasis, type 2 diabetes mellitus, and obesity are also strongly associated in adults after taking key confounding factors, such as sex, age, and smoking, into account. Results indicate a common genetic etiology for psoriasis and obesity.

Smoking and risk for psoriasis: a population-based twin study

Smoking is a potential risk factor for psoriasis. Both psoriasis and smoking habits are partly explained by genetic factors. However, twin studies investigating the association between these traits are limited.

Heritability of health-related quality of life: SF-12 summary scores in a population-based nationwide twin cohort

AIM The present study aims to estimate the relative importance of genetic and environmental factors for health-related quality of life (HRQL) measured by the 12-item Short-Form Health Survey (SF-12). METHODS The study was based on two Danish twin cohorts (46,417 twin individuals) originating from the nationwide, population-based Danish Twin Registry. The twins were approached by a mailed-out questionnaire in 2002. The questionnaire included the SF-12, information on demographic factors, and questions on a variety of specific diseases. Heritability of the SF-12 includes the physical component summary (PCS) and the mental component summary (MCS); and etiologically important variance components were estimated using multivariate biometric models. The respondents were stratified into six groups, based on age and sex. RESULTS A total of 33,794 (73%) individual twins responded to the survey. The SF-12 was completed by 29,619 individuals, which included 9,120 complete twin pairs. Overall, the best-fitting model explaining the variance of HRQL was the ACE model. The estimated heritability of the SF-12 was between 11% and 35%, whereas between 65% and 89% could be explained by unique environmental or stochastic factors in the different sex and age groups. The highest heritability was seen among older twins. In addition, the genetic correlation between MCS and PCS scores was low (0.07 and 0.23 for males and females, respectively) among younger and high (0.26 and 0.45 for males and females, respectively) in the oldest age group. Both the largest genetic influence on HRQL and the largest genetic overlap between the scores were seen in the oldest age group, which consisted of twins older than 55. The unique environmental correlation between MCS and PCS were generally negative. CONCLUSION The heritability of HRQL differs between different age groups. In general, most of the variance in the SF-12 summary components was determined by unique environmental factors.

Genetic Factors Explain Variation in the Age at Onset of Psoriasis: A Population-based Twin Study

The aim of this study was to determine the age at onset of psoriasis in a population-based twin sample. Questionnaire-data in 10,725 twin pairs, 20-71 years of age, from the Danish Twin Registry, was collected, and analysed using survival regression analysis. Median age at onset was 25 and 28 years among women and men, respectively. The correlation between the ages was 0.84 (bootstrap standard error?=?0.044) in monozygotic twin pairs and 0.60 (0.051) in dizygotic twin pairs, permutation p?=?0.001. Age at onset of psoriasis in the index twin did not predict risk of psoriasis in the co-twin, hazard ratio (per year of later onset =?1.01 (0.99-1.03), p?=?0.434. In conclusion, these data support that the age at onset of psoriasis is, in part, an inherited property. Our results do not support that early-onset psoriasis is more genetically determined.

Asthma in patients with psoriasis

DEAR EDITOR, We read with interest the report by Fang et al. of the relationship between psoriasis and asthma in a large retrospective case–control study from Taiwan. The study found a 1 38-fold increased risk of asthma among patients with psoriasis, with an increasing risk according to higher age of the patients. However, although adjustment for age, sex and selected comorbidities was performed, the study lacked important confounder control, particularly for smoking and body mass index. We studied the association between self-reported asthma and psoriasis in a previously well-described population of 34 781 Danish twins, aged 20–71 years, from the nationwide Danish Twin Registry. Psoriasis was identified by the question, ‘Has a doctor ever told you that you have, or have had psoriasis?’, whereas asthma was identified by the question, ‘Do you have, or have you ever had, asthma?’ The prevalences of psoriasis and asthma were 4 2% and 8 7%, respectively. In accordance with the study by Fang et al., we found an increased prevalence of asthma in individuals with psoriasis (10 9% vs. 8 5%), odds ratio (OR) 1 32 [95% confidence interval (CI) 1 11–1 57, P = 0 002], which remained statistically significant after adjustment for sex, age, smoking, body mass index and hospital-diagnosed chronic obstructive pulmonary disease (COPD) (OR 1 27, 95% CI 1 06–1 54; P = 0 011) (Table 1). However, adjusting also for selfreported atopic dermatitis diluted the association further (OR 1 20, 95% CI 0 99–1 45; P = 0 064), possibly due to the strong association between atopic dermatitis and asthma and/ or to recall bias and diagnostic mix-up between atopic dermatitis/other eczemas and psoriasis. Similarly, in line with the study from Taiwan, we found a higher adjusted risk of asthma in the older age group (50– 71 years) (OR 1 61, 95% CI 1 21–2 15; P = 0 001) compared with the younger age group (20–49 years) (OR 1 09, 95% CI 0 85–1 40; P = 0 51; P-value for different risks = 0 021). Furthermore, we found that the association between psoriasis and asthma was due predominantly to an increased risk of nonatopic asthma (adjusted OR 1 47, 95% CI 1 12–1 92; P = 0 005), and not atopic asthma (OR 1 19, 95% CI 0 93– 1 52; P = 0 18), using self-reported allergy to pollen, pets or dust as a proxy for atopic asthma. Finally, we found that the association between psoriasis and asthma was observed predominantly for adult-onset asthma (age at onset of asthma ≥ 18 years of age) (adjusted OR 1 40, 95% CI 1 10–1 79; P = 0 006), and not childhood-onset asthma (OR 1 06, 95% CI 0 78–1 44; P = 0 72). We also identified patients with psoriasis through the Danish National Patient Registry [International Classification of Diseases, 8th revision (ICD-8) codes 68693-4, 69609-10, 69609-19 and 69609-99; and ICD-10 code L40 0-9]. This registry records all hospitalizations and outpatient visits in Denmark. The prevalence of psoriasis by this definition was 0 6%. The risk of asthma was increased among individuals with hospital-diagnosed psoriasis compared with individuals without hospital-diagnosed psoriasis (12 5% vs. 8 7%) (OR 1 50, 95% CI 0 98–2 28; P = 0 058). This was observed particularly among the older age group (50–71 years; OR 2 12, 95% CI 1 22–3 68; P = 0 007), but less so among the younger age group (20–49 years; OR 1 07, 95% CI 0 55–2 05; P = 0 85). The risk of asthma remained statistically significantly increased in the older age group after adjustment for

Socio-demographic characteristics of Danish blood donors

Background Blood transfusion is an essential component of a modern healthcare system. Because knowledge about blood donor demography may inform the design of strategies for donor recruitment and retention, we used nationwide registers to characterize the entire population of blood donors in Denmark in 2010. Methods The study population comprised all Danes in the age range eligible for blood donation (N = 3,236,753) at the end of 2010. From the Scandinavian Donations and Transfusions (SCANDAT) register, we identified 174,523 persons who donated blood in Danish blood banks at least once in 2010. The association between sociodemographic characteristics and blood donor prevalence was examined using regression models. Results The overall prevalence of blood donation was 5.4% among both women and men. The age-specific prevalence of blood donation peaked at 25 years of age (6.8%) for women and 30 years of age (5.7%) for men. Children of any age were associated with lower prevalence of blood donation among women, while the opposite was seen for men. Middle to high income groups, but not the highest income group, had fourfold higher donor prevalence than the lowest income group (6.7% compared to 1.7%). The prevalence of blood donation was considerably lower among men living with their parents (2.9%) or alone (3.9%) than among men cohabitating with a woman (6.2%). Summary Social marginalization, as indicated by low income and being a male living without a woman, was associated with lower prevalence of blood donation. However, individuals with very high incomes and women with children were underrepresented in the Danish blood donor population.

Blood donation and risk of polycythemia vera

It has been suggested that blood donors could have an increased risk of polycythemia vera (PV). However, no study has assessed whether frequent donors have a higher PV risk than less frequent donors.

The heritability of blood donation: a population-based nationwide twin study

Voluntary blood donation is believed to be mostly motivated by altruism. Because studies have suggested that altruistic personality is determined by both genetic and environmental factors, we speculated that willingness to donate blood could also be governed by constitutional factors. This hypothesis was tested in a study among Danish twins.