Sibling risks in cancer: clues to recessive or X-linked genes?

Lung cancer risk between maternal and paternal half-siblings points to main environmental causation and targets for prevention

INTRODUCTION

Familial risk of lung cancer (LC) is at the level of many common cancers (ca 2.0) but as cigarette smoking is the main cause of LC, it has remained undefined to what extent smoking contributes to the familial risk. We take advantage of the natural experiment of divorce. In Sweden, it has been customary that children stay with their mother after divorce. We thus hypothesize that only maternal half-siblings share the childhood environment to the same extent than full siblings.

METHODS

We used Swedish nation-wide data on family structures and cancers up to year 2021 to determined LC risk (standardized incidence ratio, SIR with 95% confidence intervals) in maternal and paternal half-siblings and in full siblings.

RESULTS

Familial risk for LC in maternal half-siblings was 2.21 (1.76-2.77) which was not different from that of full siblings 2.23 (2.22-2.44). For paternal half-siblings the risk was 1.56 (1.21-2.01). For adenocarcinoma the risks were for full siblings 2.36 (2.23-2.51), for maternal half-siblings 2.55 (1.93-3.35) and for paternal half-siblings 1.33 (0.94-1.87).

CONCLUSIONS

The results showed that familial risk for LC was equal in full siblings and in maternal half-siblings; the risks for paternal half-siblings were lower and for adenocarcinoma significantly lower than those for full siblings. The results suggest that smoking is a major contributor to familial risk of LC in this setting. Smoking starts at an early age and anti-smoking campaigns should target childhood environment for prevention of smoking initiation.

Sex specific familial risk in lung cancer through changing histologies in Sweden

Familial clustering of lung cancer (LC) is related to shared smoking habits but the contribution of other potential factors such as sex or histology is not well known, and these are the subjects of the present study in Sweden. Family relationships (from Multigeneration register) and diagnosed cancers (from Cancer registry) were obtained from the national registers from 1961 to 2021. The overall familial risk for LC was constant from the 1990s but the male familial risk decreased while the female familial risk doubled at the same time when female incidence doubled. The female familial risk for mother-daughter pairs was higher (SIR = 2.2 [2.0-2.3], N = 716) than for father-son pairs (SIR = 1.6 [1.5-1.8], N = 962). The histology-specific familial risks for adenocarcinoma, squamous cell carcinoma, small cell and large cell carcinoma were highest for concordant histology but also present for discordant histology. The number of family members diagnosed with LC was a strong determinant of familial risk. The novel results showed that familial risk of LC depends on the background incidence of LC and is higher for women compared to men. We demonstrated further an increased familial risk for each of the four histological types of LC which was higher for concordant than discordant histologies but was even detected between discordant histologies suggesting that LC histology is not a genetic trait.

Identification of genes associated with testicular germ cell tumor susceptibility through a transcriptome-wide association study

Transcriptome-wide association studies (TWASs) have the potential to identify susceptibility genes associated with testicular germ cell tumors (TGCTs). We conducted a comprehensive TGCT TWAS by integrating genome-wide association study (GWAS) summary data with predicted expression models from normal testis, TGCT tissues, and a cross-tissue panel that encompasses shared regulatory features across 22 normal tissues, including the testis. Gene associations were evaluated while accounting for variant-level effects from GWASs, followed by fine-mapping analyses in regions exhibiting multiple TWAS signals, and finally supplemented by colocalization analysis. Expression and protein patterns of identified TWAS genes were further examined in relevant tissues. Our analysis tested 19,805 gene-disease links, revealing 165 TGCT-associated genes with a false discovery rate of less than 0.01. We prioritized 46 candidate genes by considering GWAS-inflated signals, correlations between neighboring genes, and evidence of colocalization. Among these, 23 genes overlap with 22 GWAS loci, with 7 being associations not previously implicated in TGCT risk. Additionally, 23 genes located within 21 loci are at least 1 Mb away from published GWAS index variants. The 46 prioritized genes display expression levels consistent with expected expression levels in human gonadal cell types and precursor tumor cells and significant enrichment in TGCTs. Additionally, immunohistochemistry revealed protein-level accumulation of two candidate genes, ARID3B and GINM1, in both precursor and tumor cells. These findings enhance our understanding of the genetic predisposition to TGCTs and underscore the importance of further functional investigations into these candidate genes.

A lean additive frailty model: With an application to clustering of melanoma in Norwegian families

Additive frailty models are used to model correlated survival data. However, the complexity of the models increases with cluster size to the extent that practical usage becomes increasingly challenging. We present a modification of the additive genetic gamma frailty (AGGF) model, the lean AGGF (L-AGGF) model, which alleviates some of these challenges by using a leaner additive decomposition of the frailty. The performances of the models were compared and evaluated in a simulation study. The L-AGGF model was used to analyze population-wide data on clustering of melanoma in 2 391 125 two-generational Norwegian families, 1960-2015. Using this model, we could analyze the complete data set, while the original model limited the analysis to a restricted data set (with cluster sizes≤ 7 $$ \le 7 $$ ). We found a substantial clustering of melanoma in Norwegian families and large heterogeneity in melanoma risk across the population, where 52% of the frailty was attributed to the 10% of the population at highest unobserved risk. Due to the improved scalability, the L-AGGF model enables a wider range of analyses of population-wide data compared to the AGGF model. Moreover, the methods outlined here make it possible to perform these analyses in a computationally efficient manner.

Familial Risk for Moyamoya Disease Among First-Degree Relatives, Based on a Population-Based Aggregation Study in Korea

BACKGROUND AND PURPOSE

Genetic factors have been known to play a role in the etiology of moyamoya disease (MMD); however, population-level studies quantifying familial risk estimates are unavailable. We aimed to quantify familial incidence and risk for MMD in first-degree relatives (FDR) in the general population of Korea.

METHODS

By using the Korean National Health Insurance database which has complete population coverage and confirmed FDR information, we constructed a cohort of 21 940 795 study subjects constituting 12 million families with blood-related FDR and followed them for a familial occurrence of MMD from 2002 to 2017. Incidence risk ratios were calculated as MMD incidence in individuals with affected FDR compared with those without affected FDR, according to age, sex, and family relationships.

RESULTS

Among total study subjects, there were 22 459 individuals with affected FDR, of whom 712 familial cases developed MMD with an incidence of 21.8/10⁴ person-years. Overall, the familial risk for MMD was 132-fold higher in individuals with versus without affected FDR. Familial risk (incidence risk ratio; incidence/10⁴ person-years) increased with the degree of genetic relatedness, being highest in individuals with an affected twin (1254.1; 230.0), followed by a sibling (212.4; 35.6), then mother (87.7; 14.4) and father (62.5; 10.4). Remarkably, there was no disease concordance between spouses. The risks were age-dependent and were particularly high in younger age groups. Familial risks were similar in males and females, and the risk of disease transmission was higher in same-sex parent-offspring and sibling pairs.

CONCLUSIONS

Our study indicates that genetic predisposition is the predominant driver in MMD pathogenesis, with minimal contribution of environmental factors. These results could be utilized to direct future genetic studies and clinical risk counseling.

Risk of Stroke in Patients With Atrial Fibrillation Is Associated With Stroke in Siblings: A Nationwide Study

Background

It remains unclear whether heritable factors can contribute to risk stratification for ischemic stroke in patients with atrial fibrillation (AF). We examined whether having a sibling with ischemic stroke was associated with increased risk of ischemic stroke and mortality in patients with AF.

Methods and Results

In this nationwide study of the Swedish population, patients with AF and their siblings were identified from the Swedish patient registers and the Swedish MGR (Multi‐Generation Register). Ischemic stroke events were retrieved from the Swedish patient registers and CDR (Cause of Death Register). Risk of ischemic stroke was compared between patients with AF with and without a sibling affected by ischemic stroke, AF, or both ischemic stroke and AF. The total study population comprised 113 988 subjects (mean age, 60±12 years) diagnosed with AF between 1989 and 2012. In total, 11 709 of them were diagnosed with a first ischemic stroke and 20 097 died during a mean follow‐up time of 5.5 years for ischemic stroke and 5.9 years for mortality. After adjustment for covariates having a sibling with ischemic stroke, or both ischemic stroke and AF, was associated with increased risk of ischemic stroke (hazard ratio, 1.31; 95% CI, 1.23–1.40 or hazard ratio, 1.36; 95% CI, 1.24–1.49, respectively). Furthermore, ischemic stroke in a sibling was associated with all‐cause mortality (hazard ratio, 1.09; 95% CI, 1.05–1.14). In contrast, the risk of stroke was only marginally increased for patients with AF with a spouse affected by ischemic stroke.

Conclusions

Having a sibling affected by ischemic stroke confers an increased risk of ischemic stroke and death independently of traditional risk factors in patients with AF.

Familial Risks of Glaucoma in the Population of Sweden

BACKGROUND

Glaucoma has a familial component but detailed data on the modification of familial risks are lacking. The aim of the study was to determine detailed familial risks for medically diagnosed glaucoma based on nationwide hospital and population records.

MATERIALS AND METHODS

Subjects were obtained from the multigeneration register, contains the Swedish population in families, and glaucoma patients were identified from the hospital discharge register (1987-2012) and the outpatient register (2001-2012). Standardized incidence ratios (SIRs) were calculated as the ratio of observed to expected number of cases.

RESULTS

Familial risks were increased in both male and female individuals. Concordant familial risks were generally higher than discordant risks. For example, familial concordant risks were SIR=3.25 (95% confidence interval, 3.16-3.35) for primary open-angle glaucoma, 9.93 (95% confidence interval, 7.30-13.22) for primary angle-closure glaucoma. Very high familial risks were observed if ≥2 relatives were affected, for example, the high-risk group of multiple affected siblings with an SIR>20. The spouse risk was modestly increased 1.20.

CONCLUSIONS AND RELEVANCE

Family history of glaucoma is a strong predictor for glaucoma, and is a potential useful tool in clinical risk assessment. Our data emphasize the contribution of familial factors to the glaucoma.

Familial Aggregation of Aortic Valvular Stenosis: A Nationwide Study of Sibling Risk

BACKGROUND

Aortic valvular stenosis (AS) is the most common cause of cardiac valvular replacement surgery. During the last century, the pathogenesis of AS has undergone transitions in developed countries, from rheumatic heart disease to a degenerative calcific pathogenesis. Although a familial component has been described for a subset of cases with a bicuspid valve, data are limited on the overall familial aggregation of this disease.

METHODS AND RESULTS

Contemporary information on 6 117 263 Swedish siblings, of which 13 442 had a clinical diagnosis of AS, was collected from the nationwide Swedish Multi-Generation Register and the National Patient Register. A total of 4.8% of AS cases had a sibling history of AS. Having at least 1 sibling with AS was associated with a hazard ratio of 3.41 (95% confidence interval, 2.23-5.21) to be diagnosed with AS in an adjusted model. Individuals with >1 sibling with AS had an exceptionally high risk (hazard ratio, 32.84) but were uncommon (34 siblings from 11 sibships). In contrast, spouses of subjects with AS were only slightly more likely to be diagnosed with AS compared with subjects without spousal AS (hazard ratio 1.16 for husbands and 1.18 for wives).

CONCLUSIONS

A sibling history of clinically diagnosed AS was associated with increased risk of AS. Spouses of patients with AS only had a modest risk increase, suggesting that shared adult environmental factors contribute less to the development of AS than genetic factors.

Linc00441 interacts with DNMT1 to regulate RB1 gene methylation and expression in gastric cancer

Recent studies revealed that several Long noncoding RNAs (LncRNAs) are associated with progression of gastric cancer (GC), while the functional role and molecular mechanism of many GC-associated lncRNAs remain undetermined. The tumor suppressor-gene retinoblastoma gene (RB1) was decreased in several human cancers including gastric cancer (GC). In this study, we investigated whether Linc00441 was involved in the suppression of RB1. Our findings showed that the up-regulated Linc00441 was inversely correlated with RB1 expression in human GC tumor samples. The gain- and loss-of-function investigation revealed that Linc00441 could promote the proliferation of GC cells. Furthermore, RNA pull down and RIP assays demonstrated that Linc00441 could recruit DNMT1 to the RB1 promoter and suppressed RB1 expression in GC cells. In conclusion, our findings revealed that Linc00441 played crucial role in GC progression and suggested that Linc00441 was potentially an effective target for GC therapy in the future.

Determination of age-specific and sex-specific familial risks for the different manifestations of venous thromboembolism: A nationwide family study in Sweden

This nationwide study aimed to determine whether differences exist in age-specific and sex-specific familial risks for pulmonary embolism (PE), venous thrombosis of the lower limbs (VT) and other forms of venous thromboembolism (OVTE) among offspring, siblings and spouses of affected individuals. The Swedish Multi-Generation Register was linked to the Hospital Discharge Register data for the period 1987–2007. Standardised incidence ratios (SIRs) were calculated for individuals whose relatives were hospitalised for venous thromboembolism (VTE), as determined by the International Classification of Diseases (ICD), and those whose relatives were unaffected by VTE. The total number of hospitalised VTE patients was 45,362. All VTE patients were categorised as PE, VT or OVTE according to ICD at first hospitalisation. For example, the parental SIRs for PE, VT and OVTE in offspring at age 10–19 years were 2.89 (95% CI 1.48–5.06), 4.99 (95% CI 3.22–6.10) and 3.89 (95% CI 2.51–5.75), respectively. The low spousal risks of PE (1.08; 95% CI 1.02–1.13), VT (1.06; 95% CI 1.011.12) and OVTE (1.07; 95% CI 1.00–1.15) suggest the familial risks to be largely genetic. In both men and women, familial relative risks were increased for all the different manifestations of VTE with the exception of those older than 70 years. Familial history is a risk indicator in both sexes, and is potentially useful for clinical risk assessment for the different manifestations of VTE.

Site-specific familial risk and survival of familial and sporadic head and neck cancer

The vast majority of head and neck cancers (HNCs) are sporadic squamous cell carcinomas, smoking and heavy drinking being the main risk factors. However, little is known about the possible role of family history and the importance of inherited factors versus shared environment. We used Swedish population-based registries to study the family history of HNC. In order to estimate the risk for family members to get the same cancer, and the risk for cancer-specific death in patients with a family history of HNC compared with patients without a family history, multivariate Cox proportional hazards analyses were performed. A 1.43-fold increased risk for developing HNC in the first-degree relatives (FDRs) of HNC patients [hazard ratio (HR), 1.43; 95% CI, 1.28-1.61] was found, when compared with relatives of healthy controls. In spouses of patients with HNC, the risk for developing any HNC was moderately increased (HR, 1.25; 95% CI, 1.01-1.53), compared with spouses of healthy controls. In addition, a 1.34-fold increased risk for death of HNC was found in HNC patients with a family history of HNC (HR, 1.34; 95% CI, (1.03-1.73) compared with HNC patients without a family history. We found an increased risk for HNC in relatives and spouses of HNC patients, when compared with family members of healthy controls. This suggests that in addition to inherited factors, shared environmental factors have a significant role in the development of the cancer. Family history of HNC was associated with worse survival in a newly diagnosed HNC patient.

Association of Family History of Type 2 Diabetes with Prostate Cancer: A National Cohort Study

Background

Personal history of type 2 diabetes mellitus (T2DM) is associated with a lower incidence of prostate cancer, but the underlying mechanisms are largely unknown. We hypothesized that genetic factors that are involved in the development of T2DM might protect against prostate cancer.

Methods

We used a few Swedish registers, including the Swedish Multigeneration Register and the Cancer Register, to examine the risk of prostate cancer among men with a family history of T2DM. Standardized incidence ratios were used to calculate the relative risk.

Results

The overall risk of prostate cancer among men with a familial history of T2DM was 0.87 (95% CI: 0.86–0.89) as compared to matched controls. The risk was even lower for those multiple affected relatives with T2DM, and it was 0.86 for those with two affected relatives and 0.67 for those with three and more affected relatives.

Conclusion

Family history of T2DM was associated with a lower incidence of prostate cancer, and the risk was even lower for those with more than one affected relative. Our study strongly suggests that genetic factors or shared familial factors, such as obesity, that contributed to T2DM may protect against prostate cancer.

Familial risks of glomerulonephritis - a nationwide family study in Sweden

OBJECTIVE

Familial risks of glomerulonephritis (acute, chronic and unspecified glomerulonephritis) have not been studied. This study aims to determine the familial risks of glomerulonephritis.

METHODS

Individuals born from1932 onwards diagnosed with glomerulonephritis (acute [n = 7011], chronic [n = 10,242] and unspecified glomerulonephritis [n = 5762]) were included. The familial risk (Standardized incidence ratio = SIR) was calculated for individuals whose parents/full-siblings were diagnosed with glomerulonephritis compared to those whose parents/full-siblings were not. The procedure was repeated for spouses. Familial concordant risk (same disease in proband and exposed relative) and discordant risk (different disease in proband and exposed relative) of glomerulonephritis were determined.

RESULTS

Familial concordant risks (parents/full-sibling history) were: SIR = 3.57 (95% confidence interval, 2.77-4.53) for acute glomerulonephritis, SIR = 3.84 (3.37-4.36) for chronic glomerulonephritis and SIR = 3.75 (2.85-4.83) for unspecified glomerulonephritis. High familial risks were observed if two or more relatives were affected; the SIR was 209.83 (150.51-284.87) in individuals with at least one affected parent as well as one full-sibling. The spouse risk was only moderately increased (SIR = 1.53, 1.33-1.75).

CONCLUSIONS

Family history of glomerulonephritis is a strong predictor for glomerulonephritis, and is a potentially useful tool in clinical risk assessment. Our data emphasize the contribution of familial factors to the glomerulonephritis burden in the community. Key Messages The familial risks (full-sibling/parent history) of glomerulonephritis (acute, chronic and unspecified glomerulonephritis) have not been determined previously. The familial risks of glomerulonephritis were increased among individuals with family history of acute, chronic or unspecified glomerulonephritis. The familial risks of glomerulonephritis were slightly increased among spouses indicating a modest non-genetic contribution. Very high familial risks were observed in multiplex families, i.e. with one or more affected first-degree relatives.

Incidence and familial risk of pleural mesothelioma in Sweden: a national cohort study

Familial clustering of pleural mesothelioma was reported previously, but none of the reports quantified the familial risk of mesothelioma or the association with other cancers. The contributions of shared environmental or genetic factors to the aggregation of mesothelioma were unknown.We used a number of Swedish registers, including the Swedish Multigeneration Register and the Swedish Cancer Register, to examine the familial risk of mesothelioma in offspring. Standardised incidence ratios (SIRs) were used to calculate the risk. Age standardised incidence rates of mesothelioma were calculated from the Swedish Cancer Registry.The incidence of mesothelioma reached its peak rate in 2000 and decreased thereafter. Risk of mesothelioma was significantly increased when parents or siblings were diagnosed with mesothelioma, with SIRs of 3.88 (95% CI 1.01-10.04) and 12.37 (95% CI 5.89-22.84), respectively. Mesothelioma was associated with kidney (SIR 2.13, 95% CI 1.16-3.59) and bladder cancers (SIR 2.09, 95% CI 1.32-3.14) in siblings. No association was found between spouses.Family history of mesothelioma, including both parental and sibling history, is an important risk factor for mesothelioma. Shared genetic factors may contribute to the observed familial clustering of mesothelioma, but the contribution of shared environmental factors could not be neglected. The association with kidney and bladder cancers calls for further study to explore the underlying mechanisms.

Family history of cancer and the risk of squamous cell carcinoma of oesophagus: a case-control study in Kashmir, India

Background:

Only a few studies have examined the association between family history of cancer (FHC) and the risk of oesophageal squamous cell carcinoma (ESCC) in high incidence areas of ESCC. We conducted a case–control study to evaluate the relationship between FHC and ESCC risk in Kashmir, India, with analysis of detailed epidemiological data and information on multiple gene polymorphisms.

Methods:

We collected detailed information on FHC and a number of socio-demographic and lifestyle factors, and also obtained blood samples for genetic analysis from 703 histopathologically confirmed ESCC cases and 1664 individually matched controls. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results:

Participants who had FHC showed a strong association with ESCC risk, and the risk was stronger when first-degree relatives (FDRs) had FHC (OR=6.8; 95% CI=4.6–9.9). Having a sibling with a cancer showed the strongest association (OR=10.8; 95% CI=6.0–19.3), but having a child with a cancer was not associated with ESCC risk. A history of any cancer in the spouse was also associated with ESCC risk (OR=4.1; 95% CI=1.6–10.2). Those with two or more relatives with FHC were at a higher risk of ESCC. After restricting FHC to familial ESCC only, the above associations were strengthened, except when spouses were affected with ESCC (OR=2.5; 95% CI=0.7–8.9). When we examined the associations between several single-nucleotide polymorphisms and ESCC in those with and without FHC, the associations of variant genotypes in cytochrome P450 (CYP) 2C19 and CYP2D6 and the wild genotype of CYP2E1 with ESCC were much stronger in those with FHC. The FHC had an additive interaction with several risk factors of ESCC in this population.

Conclusion:

Our results showed that FHC was strongly associated with ESCC risk in Kashmir. It seems both genetic factors and shared environment are involved in this association.

Familial risks of kidney failure in Sweden: a nationwide family study

Background

The value of family history as a risk factor for kidney failure has not been determined in a nationwide setting.

Aim

This nationwide family study aimed to determine familial risks for kidney failure in Sweden.

Methods

The Swedish multi-generation register on 0–78-year-old subjects were linked to the Swedish patient register and the Cause of death register for 1987–2010. Individuals diagnosed with acute kidney failure (n = 10063), chronic kidney failure (n = 18668), or unspecified kidney failure (n = 3731) were included. Kidney failure patients with cystic kidney disease, congenital kidney and urinary tract malformations, urolithiasis, and rare inherited kidney syndromes, and hyperoxaluria were excluded. Standardized incidence ratios (SIRs) were calculated for individuals whose parents/siblings were diagnosed with kidney failure compared to those whose parents or siblings were not.

Results

The concordant (same disease) familial risks (sibling/parent history) were increased for chronic kidney failure SIR = 2.02 (95% confidence interval, CI 1.90–2.14) but not for acute kidney failure SIR = 1.08 (95% CI 0.94–1.22) and for unspecified kidney failure SIR = 1.25 (95% CI 0.94–1.63). However, the discordant (different disease) familial risk for acute kidney failure SIR = 1.19 (95% CI 1.06–1.32) and unspecified kidney failure SIR = 1.63 (95% CI 1.40–1.90) was significantly increased in individuals with a family history of chronic kidney failure. The familial risk for chronic kidney failure was similar for males SIR = 2.04 (95% CI 1.90–2.20) and females SIR = 1.97 (95% CI 1.78–2.17). Familial risks for chronic kidney failure were highest at age of 10–19 years SIR = 6.33 (95% CI 4.16–9.22).

Conclusions

The present study shows that family history is an important risk factor for chronic kidney failure but to a lower degree for acute kidney failure and unspecified kidney failure.

Most common 'sporadic' cancers have a significant germline genetic component

Common cancers have been demarcated into 'hereditary' or 'sporadic' ('non-hereditary') types historically. Such distinctions initially arose from work identifying rare, highly penetrant germline mutations causing 'hereditary' cancer. While rare mutations are important in particular families, most cases in the general population are 'sporadic'. Twin studies have suggested that many 'sporadic' cancers show little or no heritability. To quantify the role of germline mutations in cancer susceptibility, we applied a method for estimating the importance of common genetic variants (array heritability, h(2)g) to twelve cancer types. The following cancers showed a significant (P < 0.05) array heritability: melanoma USA set h(2)g = 0.19 (95% CI = 0.01-0.37) and Australian set h(2)g = 0.30 (0.10-0.50); pancreatic h(2)g = 0.18 (0.06-0.30); prostate h(2)g = 0.81 (0.32-1); kidney h(2)g = 0.18 (0.04-0.32); ovarian h(2)g = 0.30 (0.18-0.42); esophageal adenocarcinoma h(2)g = 0.24 (0.14-0.34); esophageal squamous cell carcinoma h(2)g = 0.19 (0.07-0.31); endometrial UK set h(2)g = 0.23 (0.01-0.45) and Australian set h(2)g = 0.39 (0.02-0.76). Three cancers showed a positive but non-significant effect: breast h(2) g = 0.13 (0-0.56); gastric h(2)g = 0.11 (0-0.27); lung h(2)g = 0.10 (0-0.24). One cancer showed a small effect: bladder h(2)g = 0.01 (0-0.11). Among these cancers, previous twin studies were only able to show heritability for prostate and breast cancer, but we can now make much stronger statements for several common cancers which emphasize the important role of genetic variants in cancer susceptibility. We have demonstrated that several 'sporadic' cancers have a significant inherited component. Larger genome-wide association studies in these cancers will continue to find more loci, which explain part of the remaining polygenic component.

Familial testicular germ cell tumors (FTGCT) - overview of a multidisciplinary etiologic study

This Review summarizes the cumulative results of the National Cancer Institute Clinical Genetics Branch Multidisciplinary Etiologic Study of Familial Testicular Germ Cell Tumors (FTGCT). Initiated 12 years ago, this protocol enrolled 724 subjects from 147 unrelated families with either ≥2 affected men (n = 90) with TGCT or a proband with bilateral TGCT and a negative family history for this cancer (n = 57). Data were collected directly from 162 subjects evaluated at the NIH Clinical Center, and 562 subjects provided information from their home communities (Field Cohort). The primary study aims included (i) ascertaining, enrolling eligible FTGCT kindred, (ii) characterizing the clinical phenotype of multiple-case families, (iii) identifying the underlying genetic mechanism for TGCT susceptibility in families, (iv) evaluating counseling, psychosocial, and behavioral issues resulting from membership in an FTGCT family, and (v) creating an annotated biospecimen repository to permit subsequent translational research studies. Noteworthy findings include (i) documenting the epidemiologic similarities between familial and sporadic TGCT, (ii) demonstrating significantly younger age-at-diagnosis for familial vs. sporadic TGCT, (iii) absence of a dysmorphic phenotype in affected family members, (iv) shifting the focus of gene discovery from a search for rare, highly penetrant susceptibility variants to the hypothesis that multiple, more common, lower penetrance genes underlie TGCT genetic risk, (v) implicating testicular microlithiasis in FTGCT risk, and (vi) observing that aberrant methylation may contribute to FTGCT risk. A clinically based, biospecimen-intensive, multidisciplinary research strategy has provided novel, valuable insights into the etiology of FTGCT, and created a research resource which will support FTGCT clinical and laboratory studies for years to come.

Venous thromboembolism and varicose veins share familial susceptibility: a nationwide family study in Sweden

Background

Varicose veins (VVs) have been associated with venous thromboembolism (VTE), but whether these diseases share familial susceptibility has not been determined. This nationwide study aimed to determine whether VTE shares familial susceptibility with VVs.

Methods and Results

Swedish Multigeneration Register data for persons aged 0 to 76 years during the period 1964–2008 were linked to the Swedish Inpatient and Outpatient Registers. Familial risks (standardized incidence ratios [SIRs]) of VTE and VVs were examined in 2 ways (ie, bidirectionally): risk of VTE in subjects whose siblings had been diagnosed with VVs and risk of VVs in persons whose siblings had been diagnosed with VTE. The analyses were repeated for spouses to determine the importance of shared adult family environment. In total, 96 810 siblings had VVs and 87 564 had VTE. An increased risk of VTE was observed in persons whose siblings had VVs (SIR 1.30, 95% CI 1.26 to 1.33), whereas persons whose siblings had VTE had an increased risk of VVs (SIR 1.30, 95% CI 1.27 to 1.34). If 2 or more siblings were affected by VTE, the risk for VVs was 1.70 (95% CI 1.53 to 1.88). Conversely, if 2 or more siblings were affected by VVs, the risk for VTE was 1.52 (95% CI 1.38 to 1.67). In spouses of VTE patients, a minor increased risk of VVs was observed (SIR 1.05 for husbands, SIR 1.06 for wives). The risk of VTE in spouses of VV patients was similarly small (SIR 1.01 for husbands, SIR 1.05 for wives).

Conclusions

VVs and VTE share familial susceptibility. This novel finding suggests the existence of shared familial and possibly genetic factors.

A hierarchical frailty model for familial testicular germ-cell tumors

Using a 2-level hierarchical frailty model, we analyzed population-wide data on testicular germ-cell tumor (TGCT) status in 1,135,320 two-generational Norwegian families to examine the risk of TGCT in family members of patients. Follow-up extended from 1954 (cases) or 1960 (unaffected persons) to 2008. The first-level frailty variable was compound Poisson-distributed. The underlying Poisson parameter was randomized to model the frailty variation between families and was decomposed additively to characterize the correlation structure within a family. The frailty relative risk (FRR) for a son, given a diseased father, was 4.03 (95% confidence interval (CI): 3.12, 5.19), with a borderline significantly higher FRR for nonseminoma than for seminoma (P = 0.06). Given 1 affected brother, the lifetime FRR was 5.88 (95% CI: 4.70, 7.36), with no difference between subtypes. Given 2 affected brothers, the FRR was 21.71 (95% CI: 8.93, 52.76). These estimates decreased with the number of additional healthy brothers. The estimated FRRs support previous findings. However, the present hierarchical frailty approach allows for a very precise definition of familial risk. These FRRs, estimated according to numbers of affected/nonaffected family members, provide new insight into familial TGCT. Furthermore, new light is shed on the different familial risks of seminoma and nonseminoma.

Shared and nonshared familial susceptibility to surgically treated inguinal hernia, femoral hernia, incisional hernia, epigastric hernia, and umbilical hernia

BACKGROUND

The familial risk of abdominal wall hernia (AWH) is largely unknown. In addition, it is unknown whether inguinal hernia (IH), femoral hernia (FH), incisional hernia (INH), epigastric hernia (EH), and umbilical hernia (UH) share familial susceptibility. The aim of this nationwide study was to determine the familial risks of concordant AWH (same disease in proband and exposed relative) and discordant AWH (different disease in proband and exposed relative).

STUDY DESIGN

Data from the Swedish Multigeneration Register on individuals aged 0 to 78 years were linked to the Swedish hospital discharge register and the Swedish outpatient register for the period from 1964 to 2010. Standardized incidence ratios (SIRs) and 95% CIs for surgically treated IH (n = 209,814 cases), FH (n = 4,576), INH (n = 19,494), EH (n = 8,257), and UH (n = 22,761) were calculated for siblings of individuals with hernia compared with the siblings of unaffected individuals. The procedure was repeated for spouses.

RESULTS

All concordant and most discordant familial sibling risks were increased. Familial concordant SIRs for siblings were IH = 1.97 (95% CI, 1.94-1.99), FH = 3.40 (95% CI, 2.44-4.62), INH = 2.24 (95% CI, 2.04-2.46), EH = 5.57 (95% CI, 4.64-6.64), and UH = 3.61 (95% CI, 3.33-3.91). Concordant familial risks were higher than discordant risks. For example, when the proband sibling had IH, the discordant SIRs were FH = 1.74 (95% CI, 1.61-1.88), INH = 1.22 (95% CI, 1.16-1.28), EH = 1.30 (95% CI, 1.20-1.40), and UH = 1.35 (95% CI, 1.29-1.41). Concordant SIRs for spouses were lower: IH = 1.23 (95% CI, 1.20-1.26), FH = 0.97 (95% CI, 0.64-1.36), INH = 1.56 (95% CI, 1.41-1.71), EH = 1.70 (95% CI, 1.09-2.45), and UH = 1.31 (95% CI, 1.09-1.56).

CONCLUSIONS

Family history of surgically treated AWH is an important risk factor for surgical treatment of AWH. The 5 forms of AWH studied share familial susceptibility, but site-specific familial factors might exist. Several spouse risks were increased, suggesting the possibility of a nongenetic contribution to familial risks.

Familial risk of small intestinal carcinoid and adenocarcinoma

BACKGROUND & AIMS

Small intestinal cancer (SIC) is rare, and its etiology is poorly understood. We compared clusters of families with SICs of different histologic subtypes.

METHODS

By using the nationwide family cancer data sets of Sweden and Finland, we identified a cohort of 9964 first-degree relatives of 1799 patients with SIC, diagnosed from 1961 through 2009. Data were collected from time periods as long as 47 years (mean, 35.4 y), and cancer incidence was determined. Standardized incidence ratios (SIRs) were calculated and stratified by sex, age, time period, and cancer type, using the incidence rates for the entire national population as the reference.

RESULTS

Among the 1799 SIC cases, 1.1% had a sibling with SIC, so the SIR was 11.8 (95% confidence interval [CI], 7.2-18.2); 1.1% had a parent or child with SIC (SIR, 3.5; 95% CI, 2.0-5.6). The SIR of concordant carcinoid histology of SIC among siblings was 28.4 (95% CI, 14.7-49.6; n = 12) and in parent-child pairs was 9.9 (95% CI, 5.4-16.6; n = 14). The familial risk of concordant histologic subtypes increased for siblings diagnosed with adenocarcinoma, but only 2 familial cases were identified. In family members of patients with SIC of the adenocarcinoma subtype, risks of colorectal and bladder cancer were modestly but significantly increased compared with the general population. Family members of patients with SIC of the carcinoid subtype had an increased risk for kidney cancer and polycythemia vera.

CONCLUSIONS

Based on data from our population-based study, first-degree relatives of patients with small intestinal carcinoid tumors have developed these tumors with high incidence. Because of the rareness of this tumor, the absolute risk remains moderate even within families. Gastroenterologists could inform patients with small intestinal carcinoids about the familial risk and encourage counseling for their first-degree relatives. Studies are needed to identify genetic factors that affect susceptibility to SIC.

Identification of novel variants in colorectal cancer families by high-throughput exome sequencing

BACKGROUND

Colorectal cancer (CRC) in densely affected families without Lynch Syndrome may be due to mutations in undiscovered genetic loci. Familial linkage analyses have yielded disparate results; the use of exome sequencing in coding regions may identify novel segregating variants.

METHODS

We completed exome sequencing on 40 affected cases from 16 multicase pedigrees to identify novel loci. Variants shared among all sequenced cases within each family were identified and filtered to exclude common variants and single-nucleotide variants (SNV) predicted to be benign.

RESULTS

We identified 32 nonsense or splice-site SNVs, 375 missense SNVs, 1,394 synonymous or noncoding SNVs, and 50 indels in the 16 families. Of particular interest are two validated and replicated missense variants in CENPE and KIF23, which are both located within previously reported CRC linkage regions, on chromosomes 1 and 15, respectively.

CONCLUSIONS

Whole-exome sequencing identified DNA variants in multiple genes. Additional sequencing of these genes in additional samples will further elucidate the role of variants in these regions in CRC susceptibility.

IMPACT

Exome sequencing of familial CRC cases can identify novel rare variants that may influence disease risk.

Familial aggregation of childhood and adult cancer in the Utah genealogy

A small proportion of childhood cancer is attributable to known hereditary syndromes, but whether there is any familial component to the remainder remains uncertain. We explored familial aggregation of cancer in a population-based case-control study using genealogical record linkage and designed to overcome limitations of previous studies. Subjects were selected from the Utah Population Database. We compared risk of cancer in adult first-degree relatives of children who were diagnosed with cancer with the risk in relatives of children who had not had a cancer diagnosed. We identified 1,894 childhood cancer cases and 3,788 controls; 7,467 relatives of cases and 14,498 relatives of controls were included in the analysis. Relatives of children with cancer had a higher risk of cancer in adulthood than relatives of children without cancer [odds ratio (OR) 1.31, 95% confidence interval (CI) 1.11-1.56]; this was restricted to mothers and siblings and was not evident in fathers. Familial aggregation appeared stronger among relatives of cases diagnosed before 5 years of age (OR 1.48, 95% CI 1.13-1.95) than among relatives of cases who were older when diagnosed (OR 1.22, 95% CI 0.98-1.51). These findings provide evidence of a generalized excess of cancer in the mothers and siblings of children with cancer. The tendency for risk to be higher in the relatives of children who were younger at cancer diagnosis should be investigated in other large data sets. The excesses of thyroid cancer in parents of children with cancer and of any cancer in relatives of children with leukemia merit further investigation.

Colorectal cancer linkage on chromosomes 4q21, 8q13, 12q24, and 15q22

A substantial proportion of familial colorectal cancer (CRC) is not a consequence of known susceptibility loci, such as mismatch repair (MMR) genes, supporting the existence of additional loci. To identify novel CRC loci, we conducted a genome-wide linkage scan in 356 white families with no evidence of defective MMR (i.e., no loss of tumor expression of MMR proteins, no microsatellite instability (MSI)-high tumors, or no evidence of linkage to MMR genes). Families were ascertained via the Colon Cancer Family Registry multi-site NCI-supported consortium (Colon CFR), the City of Hope Comprehensive Cancer Center, and Memorial University of Newfoundland. A total of 1,612 individuals (average 5.0 per family including 2.2 affected) were genotyped using genome-wide single nucleotide polymorphism linkage arrays; parametric and non-parametric linkage analysis used MERLIN in a priori-defined family groups. Five lod scores greater than 3.0 were observed assuming heterogeneity. The greatest were among families with mean age of diagnosis less than 50 years at 4q21.1 (dominant HLOD = 4.51, α = 0.84, 145.40 cM, rs10518142) and among all families at 12q24.32 (dominant HLOD = 3.60, α = 0.48, 285.15 cM, rs952093). Among families with four or more affected individuals and among clinic-based families, a common peak was observed at 15q22.31 (101.40 cM, rs1477798; dominant HLOD = 3.07, α = 0.29; dominant HLOD = 3.03, α = 0.32, respectively). Analysis of families with only two affected individuals yielded a peak at 8q13.2 (recessive HLOD = 3.02, α = 0.51, 132.52 cM, rs1319036). These previously unreported linkage peaks demonstrate the continued utility of family-based data in complex traits and suggest that new CRC risk alleles remain to be elucidated.

Family history and risk of hospital treatment for varicose veins in Sweden

Background

Family history has been suggested as a risk factor for varicose veins, but recall bias may inflate the familial risks. The aim of this nationwide study was to determine familial risks for hospital treatment for varicose veins.

Methods

Data from the Swedish Multi-Generation Register of people aged 0-76 years were linked to Hospital Discharge Register data for 1964–2008. Standardized incidence ratios (SIRs) were calculated for individuals whose relatives were treated in hospital for varicose veins and compared with those whose relatives were not. Only main diagnoses of varicose veins were considered.

Results

A total of 39 396 people had hospital treatment for varicose veins. The familial SIR among offspring with one affected parent was 2·39 (95 per cent confidence interval 2·32 to 2·46). The SIR for those with one affected sibling was 2·86 (2·76 to 2·97). SIRs were increased in both men and women. The SIR for individuals with two or more affected siblings or with two affected parents was 5·88 (5·28 to 6·53) and 5·52 (4·77 to 6·36) respectively. The SIR for the wives of men treated for varicose veins was 1·69 (1·59 to 1·80); that for the husbands of women treated for varicose veins was 1·68 (1·58 to 1·79).

Conclusion

Using the Swedish Hospital Discharge Register, and thereby eliminating recall bias, family history of hospital treatment for varicose veins was associated with an increased risk of similar treatment among relatives. The increased spousal risk suggests a contribution from non-genetic factors.

A nationwide family study of pulmonary embolism: identification of high risk families with increased risk of hospitalized and fatal pulmonary embolism

BACKGROUND

Family history is an important risk factor for deep venous thrombosis. However, few studies have determined the importance of family history of pulmonary embolism (PE).

OBJECTIVE

This nationwide study aimed to determine the familial risks of fatal and hospitalized PE.

METHODS

The Swedish Multi-Generation Register for subjects aged 0 to 76 years old born since 1932 were linked to the Hospital Discharge Register and Cause of Death Register for the period 1964-2008. Standardized incidence ratios (SIRs) for first hospitalization or death (without previous hospitalization for PE) with a main diagnosis of PE were calculated for individuals whose parent or siblings were hospitalized with or died from PE, compared to those whose parent or siblings were not affected by PE.

RESULTS

A total of 20,860 individuals were hospitalized for PE and 862 died due to primary fatal PE (without previous hospitalization for PE). The familial SIR for individuals with one sibling with hospitalized PE was 2.49 (95% CI 1.62-3.83). The familial SIR for siblings with two affected probands was 114.29 (95% CI 56.57-223.95). The familial SIRs for individuals with a parent or sibling hospitalized for PE were significantly increased for fatal PE (1.76; 95% CI 1.38-2.21) and hospitalized PE (2.13; 95% CI 2.04-2.23). Spouses had low overall familial risk for PE (1.09; 95% CI, 1.03-1.14).

CONCLUSION

The high familial risk in multiplex sibling families suggests the existence of strong genetic risk factors for PE. Familial factors and possibly genetic factors are important risk factors for primary fatal pulmonary embolism.

Familial Risks for Diseases of Myoneural Junction and Muscle in Siblings Based on Hospitalizations and Deaths in Sweden

Diseases of the myoneural junction and muscle are disabling and some are life-threatening. Recent successes in the identification of the underlying genetic mechanisms have had profound implication for their diagnostics, treatment and classification. We define familial risks for siblings who were hospitalized for or deceased from diseases of the myoneural junction and muscle. A nationwide database on diseases of the myoneural junction and muscle was constructed by linking the Multigeneration Register on 0- to 69-year-old siblings to the Hospital Discharge Register and the Causes of Death Register from years 1987 to 2001. Standardized risk ratios (SIRs) were calculated for affected sibling pairs by comparing to those whose siblings had no diseases of myoneural junction and muscle. Among a total of 2307 patients, myasthenia gravis, muscular dystrophy and myotonic disorders were commonest diagnoses. The sibling risks for these disease were 22, 190 and 198, respectively, when a sibling was diagnosed with any disease of the myoneural junction and muscle. The concordant SIRs, both siblings presenting the same disease, were 42 for myasthenia gravis, 737 for muscular dystrophy, 2000 for congenital myopathy, 1211 for myotonic disorder, 909 for periodic paralysis and 209 for unspecified myopathy. Only a few discordant sibling pairs were noted. The very high overall SIRs for the diseases of the myoneural junction and muscle imply that the sporadic forms of these diseases are relatively rare and these diseases are overwhelmingly heritable.

Familial Risks for Main Neurological Diseases in Siblings Based on Hospitalizations in Sweden

Recent successes in identifying the underlying genetic mechanisms for neurological diseases, particularly for their Mendelian forms, have had profound implications for their diagnostics, treatment and classification. However, there has never been an attempt to compare familial risks in a systematic way among and between the main neurological diseases. Familial risks were here defined for siblings who were hospitalized because of a neurological disease in Sweden. A nationwide database for neurological diseases was constructed by linking the Multigeneration Register of 0- to 69-year-old siblings to the Hospital Discharge Register for the years 1987 to 2001. Standardized risk ratios were calculated for affected sibling pairs by comparing them to those whose siblings had no neurological disease. There were three main results. First, it was shown that all disease groups had a familial risk, with the exception of transient ischemic attacks, and the risks could be ranked from the highest (3451) for Huntington's disease to the lowest (2.1) for inflammatory diseases. Second, increased familial risks were shown for disease subtypes for which susceptibility genes or familial clustering have not been demonstrated previously, including multiple sclerosis, sleep apnea, nerve, nerve root and plexus disorders, and cerebral palsy. Third, based on the available sample size there was no convincing evidence for familial comorbidity between the disease groups, suggesting that the factors causing familial aggregation, probably usually heritable genes, are distinct for each subtype. The high familial risks for neurological disease imply heritable etiology and opportunities for identification of further susceptibility genes.

Familial risks of unusual forms of venous thrombosis: a nationwide epidemiological study in Sweden

OBJECTIVE

This is the first nationwide study to determine familial risks of unusual forms of venous thrombosis amongst offspring of affected parents and amongst siblings.

DESIGN AND SETTINGS

The Swedish Multigeneration Register of 0- to 75-year-old subjects was linked to the Hospital Discharge Register for the period 1987-2007. Standardized incidence ratios (SIRs) were calculated for individuals whose relatives were hospitalized for venous thromboembolism (VTE), as determined by the International Classification of Diseases, compared to those whose relatives were not affected by VTE.

RESULTS

The total number of hospitalized patients with VTE was 45 362, of which 1824 (4.0%) were affected by a rare thrombotic condition. The familial SIRs in cases with a history of VTE in parents or siblings were significantly increased for migrating thrombophlebitis (1.81; 95% confidence interval (CI) 1.40-2.31), portal vein thrombosis (2.35; 95% CI 1.77-3.06), vena cava thrombosis (1.96; 95% CI 1.42-2.64) and cerebral venous thrombosis (1.74; 95% CI 1.30-2.28). Budd-Chiari syndrome (SIR, 0.92; 95% CI 0.24-2.38) and renal vein thrombosis (SIR, 1.72; 95% CI 0.62-3.77) were not significantly associated with parental or sibling history of VTE; however, these two conditions were very rare, and therefore, we cannot draw any definite conclusions from this finding.

CONCLUSIONS

Family history is an important risk factor for most unusual forms of VTE. Moreover, even the paraneoplastic phenomenon, migrating thrombophlebitis (Trousseau's syndrome), is associated with a family history of VTE. Thus, our data suggest that most rare forms of VTE have a familial background.

Venous thromboembolism does not share strong familial susceptibility with coronary heart disease: a nationwide family study in Sweden

AIMS

This nationwide study aimed to determine whether venous thromboembolism (VTE) shares familial susceptibility with coronary heart disease (CHD).

METHODS AND RESULTS

Data from the Swedish Multigeneration Register for subjects aged 0-76 years old for the period 1964-2008 were linked to the Hospital Discharge Register and Cause of Death Register. Familial risks of VTE and CHD were examined in two ways: risk of CHD in offspring whose parents had been diagnosed with VTE, and risk of VTE in offspring whose parents had been diagnosed with CHD. The analyses were repeated separately for siblings and spouses. In total, 174 768 offspring had CHD and 56 302 VTE. No association between VTE and CHD was observed among siblings. Among offspring, a lower risk of CHD was observed in subjects whose parents had suffered from VTE [standardized incidence ratio (SIR) 0.94 (95% confidence interval (CI) 0.92-0.95)], while offspring of parents with CHD had an increased risk of VTE [SIR 1.03 (95% CI 1.01-1.04)]. In spouses of VTE patients, an increased risk of CHD was observed [SIR 1.02 (95% CI 1.01-1.03)]. Conversely, risk of VTE was increased among spouses of CHD patients [SIR 1.03 (95% CI 1.02-1.03)]. Subanalyses of cases of myocardial infarction and pulmonary embolism/deep venous thrombosis showed similar results.

CONCLUSION

The familial background of CHD is different from that of VTE. The present study suggests that it is unlikely that shared disease-causing mutations exist to a large extent in the population.

Familial renal cell carcinoma from the Swedish Family-Cancer Database

BACKGROUND

Reliable data on familial risks are important for clinical counselling and cancer genetics.

OBJECTIVE

To evaluate familial risks for renal cell carcinomas (RCC) through parental and sibling probands in the largest available dataset.

DESIGN, SETTING, AND PARTICIPANTS

This study examined the Swedish Family-Cancer Database on 12.2 million individuals, which contains families with parents and offspring. Cancer data were retrieved from the Swedish Cancer Registry for the years 1961-2008, including 8513 patients with RCC.

MEASUREMENTS

Familial risk for offspring was defined through standardised incidence ratios (SIRs) and adjusted for many variables, including a proxy for smoking and obesity.

RESULTS AND LIMITATIONS

The familial risk for RCCs was 1.75 when a parent and 2.61 when a sibling was diagnosed with any kidney cancer. Also, RCCs were shown to be associated with prostate cancer (PCa) when parents or parents and siblings were diagnosed with PCa. Among siblings, the associations of RCC with melanoma, non-Hodgkin's lymphoma, and urinary bladder and papillary thyroid tumours were found. None of the results differed significantly after excluding the families with cancer pathognomonic of a von Hippel-Lindau (VHL) disease. Limitations of this study include the small number of familial cases (229 familial cases).

CONCLUSIONS

The present analysis showed a high familiarity for RCC, and recessive effects may be important for familial aggregation of RCC. As a novel association, offspring RCC was in excess when parents or parents and siblings were diagnosed with PCa. There is familial clustering beyond VHL and the recent low-risk gene that probably explains a small proportion of the observed familial clustering.

Does family history of cancer modify the effects of lifestyle risk factors on esophageal cancer? A population-based case-control study in China

A population-based case-control study on esophageal cancer has been conducted since 2003 in Jiangsu Province, China. The aim of this analysis is to provide further evidence on the relationship between family history of cancer in first-degree relatives (FH-FDRs) and the risk of esophageal cancer, and to explore the joint effects for FH-FDR with major lifestyle risk factors. A total of 1,520 cases and 3,879 controls were recruited. Unconditional logistic regression was applied for evaluating independent association as well as potential interactions between FH-FDR and lifestyle risk factors on the risk of esophageal cancer. Population attributable fraction (PAF) was calculated to quantify the proportion of cases attributable to risk factors. Results showed that with a FH-FDR of any malignant tumor or esophageal cancer, there is a 1.64- and 2.22-fold risk of esophageal cancer, respectively. Association was increased when there was more than one affected FDR (OR = 3.14) and younger age at diagnosis of relatives. Exposure of both FH-FDR and lifestyle risk factors strongly associated with esophageal cancer. Significant superadditivity interaction was found for FH-FDR with fast eating speed and diets low in fruits and vegetables. The estimation of PAF indicated that the majority of cases were attributed to lifestyle risk factors. In conclusion, it was found that FH-FDR significantly increases the risk of esophageal cancer and could modify the effect of certain lifestyle risk factors. If comprehensive lifestyle interventions are carried out within high-risk populations, there is a high probability of curbing occurrences of esophageal cancer.

Sibling risk of anxiety disorders based on hospitalizations in Sweden

AIMS

This study used nationwide hospital records to examine sibling risk of any type of anxiety disorder in Sweden over a 40-year period.

METHODS

This study, carried out between 1 January 1968 and 31 December 2007, of the entire population of Sweden, linked information on family relationships from the nationwide Multi-Generation Register with information from the nationwide Swedish Hospital Discharge Register on first diagnosis of anxiety disorder. A total of 42,602 persons hospitalized for anxiety disorders and 2093 affected siblings were identified. Standardized incidence ratios (SIR) were calculated by comparing risk in siblings of persons hospitalized for anxiety disorders with risk in persons whose siblings had no hospital diagnosis of anxiety disorders.

RESULTS

The sibling risk was 2.26, which was independent of sex and age differences between siblings. The SIR was highest in siblings <20 years of age (2.83). Analysis of risk by subtype showed that having a sibling diagnosed with any anxiety disorder resulted in increased risks of a number of disorders; the highest increased risk was of social phobia (SIR 3.68, 95% confidence interval, 1.68-7.69). Risk of panic disorder, generalized anxiety disorder, mixed anxiety and depressive disorder, and obsessive-compulsive disorder was raised in female but not male siblings.

CONCLUSIONS

Heritable effects likely play an important role in the cause of anxiety disorders, but the extent of their role remains to be established. Important contributions could be made by studies of gene-environment interactions that have sufficient sample sizes to produce reliable results.

Parental history and venous thromboembolism: a nationwide study of age-specific and sex-specific familial risks in Sweden

BACKGROUND

The value of parental history as a risk indicator for venous thromboembolism (VTE) has not been determined in a nationwide setting.

OBJECTIVES

To perform the first nationwide study of age-specific and sex-specific familial VTE risks in offspring of parents hospitalized for VTE.

PATIENTS/METHODS

The Swedish Multigeneration Register of 0-75-year-old subjects was linked to the Hospital Discharge Register for 1987-2007. Standardized incidence ratios (SIRs) were calculated for individuals whose parents were hospitalized for VTE as compared with those whose parents were unaffected.

RESULTS

Among 45,362 hospitalized offspring cases with VTE, 4865 offspring of affected parents were identified with a familial SIR of 2.00 (95% confidence interval [CI] 1.94-2.05). Familial SIR was slightly higher for male offspring than for female offspring (2.08, 95% CI 2.00-2.16 vs. 1.91, 95% CI 1.84-1.99). The risk in offspring was further increased when both parents were affected (3.97, 95% CI 3.40-4.61), with high familial risks at ages 20-29 years (10.00, 95% CI 5.91-15.84). The familial risks for VTE among offspring were increased from the age of 10 years up to 75 years, with familial SIRs of 3.96 (95% CI 3.13-4.94) at age 10-19 years and 1.48 (95% CI 1.17-1.84) at ages 70-75 years. However, the absolute incidence rate increased with age.

CONCLUSIONS

Parental history is potentially useful for risk assessments of VTE, although age needs to be considered. Our results support the use of an age-dependent multicausal model to estimate the risk of VTE.

Familial risks in nervous system tumours: joint Nordic study

Background:

Familial nervous system cancers are rare and limited data on familial aspects are available particularly on site-specific tumours.

Methods:

Data from five Nordic countries were used to analyse familial risks of nervous system tumours. Standardised incidence ratios (SIRs) were calculated for offspring of affected relatives compared with offspring of non-affected relatives.

Results:

The total number of patients with nervous system tumour was 63 307, of whom 32 347 belonged to the offspring generation. Of 851 familial patients (2.6%) in the offspring generation, 42 (4.7%) belonged to the families of a parent and at least two siblings affected. The SIR of brain tumours was 1.7 in offspring of affected parents; it was 2.0 in siblings and 9.4 in families with a parent and sibling affected. For spinal tumours, the SIRs were much higher for offspring of early onset tumours, 14.0 for offspring of affected parents and 22.7 for siblings. The SIRs for peripheral nerve tumours were 16.3 in offspring of affected parents, 27.7 in siblings and 943.9 in multiplex families.

Conclusion:

The results of this population-based study on medically diagnosed tumours show site-, proband- and age-specific risks for familial tumours, with implications for clinical genetic counselling and identification of the underlying genes.

Risk of cancer following hospitalization for type 2 diabetes

The present study assessed subsequent cancer risks in type 2 diabetes patients first hospitalized for this disease at age >39 years. Twenty-four cancer types showed an elevated risk when follow-up was started after the last hospitalization for type 2 diabetes. No additional risk was found in familial diabetics.

Objectives.

Cancer and type 2 diabetes (T2D) are two common diseases that may share risk factors. We aimed at determining subsequent cancer risks in patients hospitalized for T2D in Sweden.

Methods.

T2D patients were obtained from the nationwide Hospital Discharge Register; cancers were recorded from the Swedish Cancer Registry. Standardized incidence ratios (SIRs) were calculated for cancer following last hospitalization for T2D. The comparison group was the general Swedish population.

Results.

The number of hospitalized T2D patients from 1964 to 2007 was 125,126, of whom 26,641 had an affected family member. Altogether 24 cancers showed an elevated risk when follow-up was started after the last hospitalization. The highest SIRs were for pancreatic (6.08) and liver (4.25) cancers. The incidences of these cancers were even elevated when follow-up was started 5 years after the last hospitalization for T2D, with primary liver cancer showing the highest SIR of 4.66. Also increased were the incidences of upper aerodigestive tract, esophageal, colon, rectal, pancreatic, lung, cervical, endometrial, ovarian, and kidney cancers. Prostate cancer showed a lower risk. Familial T2D patients showed no exceptional elevated cancer risks but their prostate cancer and melanoma risks were lower.

Conclusions.

This study, covering approximately one half of Swedish T2D patients, showed an elevated risk for several cancers after hospitalization for T2D, probably indicating the profound metabolic disturbances of the underlying disease. The highest risks were found for liver and pancreatic cancers. No excess cancer risks were observed in familial diabetics. The lower risk for prostate cancer remains intriguing.

Familial risks for type 2 diabetes in Sweden

OBJECTIVE

Our aim was to characterize familial risks for type 2 diabetes by the type and number of affected family members, including half-siblings, adoptees, and spouses, to quantify risks and estimate the contribution of environmental effect.

RESEARCH DESIGN AND METHODS

Families were identified from the Multigeneration Register, and type 2 diabetic patients were obtained from the Hospital Discharge Register. Standardized incidence ratios were calculated for offspring with type 2 diabetes whose family members were hospitalized for type 2 diabetes at ages >39 years compared with those lacking affected family members.

RESULTS

The number of hospitalized type 2 diabetic patients was 157,549. Among 27,895 offspring, 27.9% had a parent or sibling also hospitalized for type 2 diabetes. The familial relative risk (RR) ranged from 2.0 to >30, depending on the number and type of probands. The highest RRs of type 2 diabetes were found in individuals who had at least two siblings affected by type 2 diabetes, irrespective of the parental disease. Adoptees showed no risk from adopted parents.

CONCLUSIONS

The study, the largest yet published, showed that familial RRs varied by the number and type of affected family member. However, much of the familial clustering remains yet to be genetically explained. The high risk should be recognized in clinical genetic counseling. The data from adoptees confirmed the genetic basis of the familial associations, but those from half siblings and spouses suggested that a smaller part of familial clustering may be accounted for by environmental factors.

Familial association of inflammatory bowel diseases with other autoimmune and related diseases

OBJECTIVES

Familial risk estimates are useful for genetic counseling, etiological understanding, and design of gene identification studies. We wanted to estimate the associations of ulcerative colitis (UC) and Crohn's disease (CD) with 32 autoimmune and related diseases among parents and offspring, singleton siblings, twins, and spouses.

METHODS

The Multigeneration Register in Sweden provides reliable access to information on families among 11.5 million individuals throughout the last century. The diseases in individual family members were obtained through linkage to the Hospital Discharge Register. Standardized incidence ratios (SIRs) and 95% confidence intervals were calculated as relative risks for UC/CD in family members of patients diagnosed with any of the 34 diseases compared with those lacking affected family members through years 1964-2004.

RESULTS

Among a total of 441,642 patients diagnosed with autoimmune and related conditions, 25,846 were diagnosed with UC and 18,885 with CD. Familial cases amounted to 5.4% of all UC patients and 6.5% of CD patients. SIR for UC was 3.9 (95% confidence interval 3.5-4.3) in offspring of affected parents, 4.6 (3.0-7.4) in siblings, 10.4 (6.5-15.8) in families of affected parents and siblings, and 6.3 (1.9-17.7) for monozygotic twins. The respective SIRs for CD were 6.0 (5.4-6.7), 6.3 (4.1-9.8), 34.0 (24.9-45.3), and 23.4 (10.1-51.1). All discordant associations, i.e., those between CD and other diseases, were also found for UC, including ankylosing spondylitis, asthma, polymyalgia rheumatica, psoriasis, and sarcoidosis. For UC, six additional associations were observed. No correlations between specific diseases were found among spouses, but between UC or CD and any disease it was 1.1 (1.0-1.1).

CONCLUSIONS

The concordant familial risks for UC and CD were lower than those commonly cited. Both diseases are associated with several autoimmune and related diseases, suggesting genetic sharing.