Bias in using family history as a risk factor in case-control studies of disease

Use of family history of cardiovascular disease or chronic hypertension to better identify who needs postpartum cardiovascular risk screening

BACKGROUND

Individuals with pregnancies complicated by hypertensive disorders of pregnancy are at increased risk of cardiovascular disease. However, not all who have hypertensive disorders of pregnancy are at risk, and not all who have uncomplicated pregnancies are without risk.

OBJECTIVE

This study aimed to determine if use of first-degree family history of cardiovascular disease or chronic hypertension better identifies individuals who need postpartum cardiovascular risk screening.

STUDY DESIGN

Participants were included if they had pregnancies complicated by hypertensive disorders of pregnancy or uncomplicated, term pregnancies. Individuals with a first-degree relative with chronic hypertension, myocardial infarction, or stroke were deemed to have a positive family history and were thus included.

RESULTS

Four groups were considered: 302 individuals with hypertensive disorders of pregnancy who had a positive family history, 218 individuals with hypertensive disorders of pregnancy with no family history, 39 control individuals with a positive family history, and 63 control individuals with no family history. Among individuals with hypertensive disorders of pregnancy, those with a positive family history were more likely to be diagnosed with chronic hypertension, and to have elevated 30-year lipid, 30-year body mass index, and lifetime cardiovascular disease risk score (all P<.05). Among individuals with uncomplicated pregnancies, those with a positive family history were more likely to be diagnosed with chronic hypertension (P<.05) and meet criteria for metabolic syndrome (P<.05).

CONCLUSION

First-degree family history of cardiovascular disease and/or chronic hypertension can be used to reliably identify individuals without pregnancy complications who should have postpartum cardiovascular risk screening, and may better determine which individuals who have a pregnancy complicated by hypertensive disorders of pregnancy would most benefit from postpartum cardiovascular risk screening.

Differential item functioning to validate setting of delivery compatibility in PROMIS-global health

PURPOSE

Patient-reported outcomes measures (PROMs) such as PROMIS are increasingly utilized in healthcare to assess patient perception and functional status, but the effect of delivery setting remains to be fully investigated. To our knowledge, no current study establishes the absence of differential item functioning (DIF) across delivery setting for these PROMIS- Global Health (PROMIS-GH) measures among orthopedic patients. We sought to investigate the correlation of PROMIS-GH scores across in-clinic versus remote delivery by evaluating DIF within the Global Physical Health (GPH) and Global Mental Health (GMH) items. We hypothesize that the setting of delivery of the GPH and GMH domains of PROMIS-GH will not impact the results of the measure, allowing direct comparison between the two delivery settings.

METHODS

Five thousand and seven hundred and eighty-five complete PROMIS-Global Health measures were analyzed retrospectively using the 'Lordif' package on the R platform. DIF was measured for GPH and GMH domains across setting of response (in-clinic vs remote) during the pre-operative period, immediate post-operative period, and 1-year post-operative period using Monte Carlo estimation. McFadden pseudo-R2 thresholds (> 0.02) were used to assess the magnitude of DIF for individual PROMIS items.

RESULTS

No GPH or GMH items contained in the PROMIS-GH instrument yielded DIF across in-clinic vs remote delivery setting during the pre-operative, immediate post-operative, or 1-year post-operative window.

CONCLUSION

The GPH and GMH domains within the PROMIS-GH instrument may be delivered in the clinic or remotely with comparable accuracy. This cross-delivery setting validation analysis may aid to improve the quality of patient care by allowing mixed platform PROMIS-GH data tailored to individual patient circumstance.

Systematic review with meta-analysis: the effects of family history on the risk of Barrett's oesophagus and oesophageal adenocarcinoma

BACKGROUND

Current guidelines recommend different screening approaches for individuals with a family history of Barrett's oesophagus (BO) or oesophageal adenocarcinoma (OAC), varying from no screening to screening all individuals with a positive family history.

AIMS

To determine evidence-based risk estimates for individuals with a family history of BO or OAC METHODS: We systematically searched Pubmed, Embase and Cochrane Library until October 2020 to identify all studies that reported on the association between family history and the risk of BO and OAC. Pooled summary estimates of adjusted relative risks and prevalence of familial BO/OAC with 95% confidence intervals (CIs) were calculated using a random effects model.

RESULTS

Fourteen studies comprising 16 189 BO/OAC patients were analysed. Familial clustering was seen in 8.84% (95% CI: 5.54-13.82) and 4.37% (95% CI: 2.15-8.69) of patients with BO and OAC, respectively (nine studies). Screening first-degree relatives of BO patients had a diagnostic yield between 12% and 44% for BO (four studies). However, the yield for high-grade dysplasia and OAC was low (<2%). Individuals with a positive family history had a higher risk of having BO (aRR 3.26; 95% CI 1.43-7.40; I²  = 46%; three studies) and OAC (aRR 2.19; 95% CI 1.14-4.21; I²  = 48%; five studies) compared to individuals without a family history.

CONCLUSIONS

A verified family history of BO or OAC is a strong risk factor for both BO and OAC. A positive family history could be a clinically meaningful way to identify high-risk individuals who may benefit from early detection strategies.

Familial Risk and Its Interaction With Body Mass Index and Physical Activity in Anterior Cruciate Ligament Injury Among First-Degree Relatives: A Population-Based Cohort Study

BACKGROUND

Genetic and behavioral risk factors have been suggested to play a role in anterior cruciate ligament (ACL) injury. However, population-based familial risk estimates are unavailable.

PURPOSE

To quantify familial risk of ACL injury among first-degree relatives (FDRs) after controlling for certain behavioral risk factors. To estimate the combined effect of family history and body mass index (BMI) or physical activity on the risk of ACL injury.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Using nationwide data from the Korean National Health Insurance and National Health Screening Program databases on kinship, lifestyle habits, and anthropometrics, 5,184,603 individuals with blood-related FDRs were identified from 2002 to 2018. Familial risk of ACL injury, as represented as incidence risk ratios (IRRs) with 95% CIs, was analyzed using Cox proportional hazards models among individuals with versus without affected FDRs. Analyses were adjusted for age, sex, and behavioral risk factors. Interaction testing between familial history and BMI or physical activity was performed on an additive scale.

RESULTS

The risk of ACL injury was 1.79-fold higher (IRR, 1.79; 95% CI, 1.73-1.85) among individuals with versus without affected FDRs, and the incidence was 12.61 per 10,000 person-years. The IRR (95% CI) was highest with affected twins at 4.49 (3.01-6.69), followed by siblings at 2.31 (2.19-2.44), the father at 1.58 (1.49-1.68), and the mother at 1.52 (1.44-1.61). High BMI and high level of physical activity were significantly associated with the risk of ACL injury. Individuals with positive family history and either high BMI or physical activity had a 2.59- and 2.45-fold increased risk of injury as compared with the general population, respectively, and the combined risks exceeded the sum of their independent risks.

CONCLUSION

Familial factors are risk factors for ACL injury with an additional contribution of 2 behavioral factors: BMI and physical activity level. A significant interaction was observed between family history of ACL injury and high BMI/level of physical activity.

Familial Risk of Hashimoto's Thyroiditis Among First-Degree Relatives: A Population-Based Study in Korea

Background: Few small-scale studies have reported a genetic and familial predisposition in Hashimoto's thyroiditis (HT), however, quantified familial risk estimates from population-level data are unavailable. We aimed to estimate the incidence and familial risk of HT among first-degree relatives (FDR) according to age, sex, and family relationships. Methods: We conducted a population-based study in the general population of Korea from 2002 to 2017. Using the nationwide health insurance database, which has full population coverage and family relationship information, a cohort of 22 million individuals with blood-related FDR comprising 12 million families were followed up for a familial occurrence of HT. Age- and sex-adjusted incidence risk ratios (IRRs) were calculated in individuals with an affected FDR compared with those without an affected FDR. Results: Among 21,940,795 individuals, 234,912 had an HT-affected FDR, of whom 2425 familial cases developed HT with an incidence of 7.12/10,000 person-years. The familial risk for HT was 6.5-fold (95% confidence interval [CI]: 6.24-6.78) higher in individuals with versus without affected FDR. According to relationship, familial risks were IRR 102.71, IRR 7.80, IRR 5.54, and IRR 5.52 with an affected twin, sibling, mother, and father, respectively, and the corresponding incidence (/10,000 person-years) was 115.57, 10.66, 5.73, and 5.91. Same-sex twins had three times higher risk of developing HT than opposite-sex twins (IRR 121.01 vs. 21.46). The sex-specific familial risk was higher in males than females. The risks demonstrated age dependence, being higher in younger age groups. Conclusions: This study represents the largest population-based study of familial HT risk in Asia. We demonstrated elevated familial risk of incident HT among FDR, but with lower magnitude as those observed in previous studies. Familial risk increased with the degree of genetic relatedness among FDR indicating a prominent role of genetic factors in the familial aggregation of HT. Elevated risks in the younger age groups should motivate clinicians to screen people with a family history, especially those <30 years.

Familial risk for endometriosis and its interaction with smoking, age at menarche and body mass index: a population-based cohort study among siblings

OBJECTIVE

To quantify familial risk of endometriosis among full siblings and examine interactions between family history and smoking, age at menarche or body mass index (BMI).

DESIGN, SETTING AND POPULATION

Population-based nationwide cohort study.

METHODS

Using data from the Korean National Health Insurance and Screening Programme databases on kinship, healthcare utilisation, lifestyle and anthropometrics, we identified 2 109 288 women with full siblings and their environmental risk factors from 2002 to 2018. Familial risks were estimated using Cox proportional-hazards models, represented as incidence risk ratios (IRR) with 95% CI. Interaction between family history and smoking, age at menarche or BMI were assessed on an additive scale.

MAIN OUTCOME MEASURES

IRR of endometriosis among women with and without affected siblings.

RESULTS

From 19 195 women with affected siblings, 1126 developed endometriosis with an incidence of 35.45/10 000 person-years. Familial risk of endometriosis with versus without affected siblings was increased to IRR 2.75 (95% CI 2.25-3.36), and the highest risk was with affected twins (IRR 6.98; 95% CI 4.19-11.62). Women with both a family history and either smoking, early menarche or low BMI had a significantly higher risk of endometriosis compared with the general population and can be regarded as a high-risk group, the IRRs were 4.28 (95% CI 2.43-7.55), 3.47 (95% CI 2.82-4.26) and 3.09 (95% CI 2.68-3.56), respectively. Substantial effect modification of the associations was noted by smoking and early menarche, as their combined risk with family history exceeded the sum of their individual risks, which was also statistically significant.

CONCLUSION

Genetic factors are the primary contributor to the familial aggregation of endometriosis. Significant gene-environment interaction exists between family history and smoking or early menarche.

A family affair: Evidence of chain migration during the mass emigration from the county of Halland in Sweden to the United States in the 1890s

This paper examines the influence of individual and household factors on an individual's propensity to emigrate from Halland, a region in south-west Sweden, to the United States during the era of mass migration in the late nineteenth century. The study has a case-control design, using individual-level longitudinal data for a group of emigrants (cases) and a group of non-emigrants (controls). Results indicate the importance of a family's emigration history; individuals whose relatives had previously moved to the United States were more likely to emigrate themselves. In addition, the results also show how this impact varied between groups and how other factors relating to the individual's life situation affected the migration decision. Thus, this paper shows how chain migration and migration networks play important roles during times of mass migration.

Basic vs More Complex Definitions of Family History in the Prediction of Coronary Heart Disease: The Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

To determine whether family history of coronary heart disease (FH) definitions differ in their association with atherosclerotic cardiovascular disease (ASCVD) events.

PATIENTS AND METHODS

Participants who provided FH data from July 17, 2000, through February 24, 2004, were identified. Definitions of FH were any, premature, and Familial Risk Assessment (FRA). Outcomes included coronary heart disease (CHD), stroke, peripheral artery disease, angina, and congestive heart failure. Multivariable-adjusted Cox models examined the association of FH definitions with events. C statistics and the net reclassification index examined the incremental prognostic contribution of each definition.

RESULTS

In 6200 participants, the proportions of any FH and premature FH were 36% and 16%, respectively, and of weak, moderate, and strong familial risk were 20%, 16%, and 20%, respectively. Over median follow-up of 10.1 years (range, 0.02-11.5 years), 741 participants experienced a composite event. Compared with no FH, any FH was associated with incident CHD, angina, and composite ASCVD (hazard ratios [95% CIs]: 1.4 [1.1-1.8], 1.6 [1.2-2.1], and 1.3 [1.1-1.5], respectively). Similar results were obtained for premature FH compared with no FH and for strong compared with weak FRA for these 3 outcomes. There was no association between the FH definitions and noncoronary cardiovascular events. Compared with traditional risk factors (C statistic = 0.740), any FH, premature FH, and FRA all improved discrimination of composite ASCVD (all P < .01); however, the differences in C statistics among any FH (0.743), premature FH (0.742), and FRA (0.744) were numerically small, as were differences in the net reclassification index.

CONCLUSION

A single question regarding the presence of FH in any first-degree relative performs just as well as more complicated assessments in predicting CHD.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00005487.

Risk of pancreatic cancer associated with family history of cancer and other medical conditions by accounting for smoking among relatives

Background

Family history (FH) of pancreatic cancer (PC) has been associated with an increased risk of PC, but little is known regarding the role of inherited/environmental factors or that of FH of other comorbidities in PC risk. We aimed to address these issues using multiple methodological approaches.

Methods

Case-control study including 1431 PC cases and 1090 controls and a reconstructed-cohort study (N = 16 747) made up of their first-degree relatives (FDR). Logistic regression was used to evaluate PC risk associated with FH of cancer, diabetes, allergies, asthma, cystic fibrosis and chronic pancreatitis by relative type and number of affected relatives, by smoking status and other potential effect modifiers, and by tumour stage and location. Familial aggregation of cancer was assessed within the cohort using Cox proportional hazard regression.

Results

FH of PC was associated with an increased PC risk [odds ratio (OR) = 2.68; 95% confidence interval (CI): 2.27-4.06] when compared with cancer-free FH, the risk being greater when ≥ 2 FDRs suffered PC (OR = 3.88; 95% CI: 2.96-9.73) and among current smokers (OR = 3.16; 95% CI: 2.56-5.78, interaction FHPC*smoking P-value = 0.04). PC cumulative risk by age 75 was 2.2% among FDRs of cases and 0.7% in those of controls [hazard ratio (HR) = 2.42; 95% CI: 2.16-2.71]. PC risk was significantly associated with FH of cancer (OR = 1.30; 95% CI: 1.13-1.54) and diabetes (OR = 1.24; 95% CI: 1.01-1.52), but not with FH of other diseases.

Conclusions

The concordant findings using both approaches strengthen the notion that FH of cancer, PC or diabetes confers a higher PC risk. Smoking notably increases PC risk associated with FH of PC. Further evaluation of these associations should be undertaken to guide PC prevention strategies.

Higher Fitness Is Strongly Protective in Patients with Family History of Heart Disease: The FIT Project

BACKGROUND

Cardiorespiratory fitness protects against mortality; however, little is known about the benefits of improved fitness in individuals with a family history of coronary heart disease. We studied the association between cardiorespiratory fitness and risk of incident coronary heart disease and all-cause mortality, hypothesizing an inverse relationship similar to individuals without a family history of coronary heart disease.

METHODS

We included 57,999 patients (aged 53 ± 13 years; 49% were female; 29% were black) from the Henry Ford Exercise Testing (FIT) Project. Cardiorespiratory fitness was expressed in metabolic equivalents of task based on exercise stress testing. Family history was determined as self-reported coronary heart disease in a first-degree relative at any age. We used Cox proportional hazards models adjusted for demographics and cardiovascular disease risk factors to examine the association between cardiorespiratory fitness and risk of incident coronary heart disease and mortality over a median (interquartile range) follow-up of 5.5 (5.6) and 10.4 (6.8) years, respectively.

RESULTS

Overall, 51% reported a positive family history. Each 1-unit metabolic equivalent increase was associated with lower incident coronary heart disease and mortality risk regardless of family history status. The hazard ratio and 95% confidence interval for a negative family history and a positive family history were 0.87 (0.84-0.89) and 0.87 (0.85-0.89) for incident coronary heart disease and 0.83 (0.82-0.84) and 0.83 (0.82-0.85) for mortality, respectively. There was no significant interaction between family history and categoric cardiorespiratory fitness, sex, or age (P >.05 for all).

CONCLUSIONS

Higher cardiorespiratory fitness is strongly protective in all patients regardless of family history status, supporting recommendations for regular exercise in those with a family history.

Family history of esophageal cancer increases the risk of esophageal squamous cell carcinoma

A population-based case-control was performed to explore familial aggregation of esophageal squamous cell carcinoma (ESCC). Family history of cancer was assessed by a structured questionnaire, and from which 2 cohorts of relatives of cases and controls were reconstructed. Unconditional logistic regression and Cox proportional hazards regression were applied for case-control design and reconstructed cohort design, respectively. We observed a close to doubled risk of ESCC associated with a positive family history of esophageal cancer among first degree relatives (odds ratio [OR] = 1.85, 95% confidence interval [CI]: 1.42–2.41), after adjusting age, sex, family size and other confounders. The excess risks of ESCC increased with the increasing of first-degree relatives affected by esophageal cancer (p < 0.001). In particular, those individuals whose both parents with esophageal cancer had an 8-fold excess risk of ESCC (95% CI: 1.74–36.32). The reconstructed cohort analysis showed that the cumulative risk of esophageal cancer to age 75 was 12.2% in the first-degree relatives of cases and 7.0% in those of controls (hazard ratio = 1.91, 95% CI: 1.54–2.37). Our results suggest family history of esophageal cancer significantly increases the risk for ESCC. Future studies are needed to understand how the shared genetic susceptibility and/or environmental exposures contribute to the observed excess risk.

Family history of skin cancer is associated with early-onset basal cell carcinoma independent of MC1R genotype

BACKGROUND

As a marker of genetic susceptibility and shared lifestyle characteristics, family history of cancer is often used to evaluate an individual's risk for developing a particular malignancy. With comprehensive data on pigment characteristics, lifestyle factors, and melanocortin 1 receptor (MC1R) gene sequence, we sought to clarify the role of family history of skin cancer in early-onset basal cell carcinoma (BCC).

MATERIALS AND METHODS

Early onset BCC cases (n=376) and controls with benign skin conditions (n=383) under age 40 were identified through Yale dermatopathology. Self-report data on family history of skin cancer (melanoma and non-melanoma skin cancer), including age of onset in relatives, was available from a structured interview. Participants also provided saliva samples for sequencing of MC1R.

RESULTS

A family history of skin cancer was associated with an increased risk of early-onset BCC (OR 2.49, 95% CI 1.80-3.45). In multivariate models, family history remained a strong risk factor for early-onset BCC after adjustment for pigment characteristics, UV exposure, and MC1R genotype (OR 2.41, 95% CI 1.74-3.35).

CONCLUSIONS

Risk for BCC varied based upon the type and age of onset of skin cancer among affected relatives; individuals with a first-degree relative diagnosed with skin cancer prior to age 50 were at highest risk for BCC (OR 4.79, 95% CI 2.90-7.90). Even after taking into account potential confounding effects of MC1R genotype and various lifestyle factors that close relatives may share, family history of skin cancer remained strongly associated with early-onset BCC.

Gender Difference in the Interaction Effects of Diabetes and Hypertension on Stroke among the Elderly in the Shih-Pai Study, Taiwan

Aims

To investigate the interaction effects of diabetes and hypertension on stroke, and also investigate the independent and interaction effects of parental history and environmental factors on diabetes and hypertension in a cross-sectional elderly population.

Methods

The Shih-Pai Community Medical Service Program was a community-based, fixed cohort study conducted between June 1999 and November 2002. Socio-demographic and clinical data of subjects aged 65 years and older were collected by well-trained interviewers during home visits. Interaction effects were analyzed using Rothman’s synergy index (SI).

Results

In total, 4,124 subjects were included in the study, with 2,284 males and 1,840 females. The synergistic interaction of diabetes and hypertension on stroke was statistically significant in women (SI = 3.16, 95% CI: 1.35–7.39). The synergistic interaction of parental diabetes and being overweight on diabetes was only statistically significant in men, and not in women (SI = 3.30, 95% CI: 1.00–10.83 in men, and SI = 1.15, 95% CI: 0.30–4.39 in women).

Conclusions

A synergistic interaction was found for diabetes and hypertension in both sexes when parental history and being overweight were combined. Furthermore, combining diabetes and hypertension in elderly women was significant in terms of the risk of stroke. Strategies to control risk factors in individuals at additional high risk are urgently needed.

Coronary Artery Calcium Improves Risk Assessment in Adults With a Family History of Premature Coronary Heart Disease: Results From Multiethnic Study of Atherosclerosis

BACKGROUND

The prognostic value of coronary artery calcium (CAC) or carotid intima-media thickness (CIMT) among asymptomatic adults with a family history (FH) of premature coronary heart disease is unclear.

METHODS AND RESULTS

Multiethnic Study of Atherosclerosis enrolled 6814 adults without known atherosclerotic cardiovascular disease (ASCVD). Hard ASCVD events were ascertained over a median follow-up of 10.2 years. We estimated adjusted-hazard ratios for CAC and CIMT categories using Cox regression, both within and across FH status groups. Improvement in discrimination with CAC or CIMT added to variables from the ASCVD pooled cohort equation was also evaluated using receiver-operating characteristic curve and likelihood ratio analysis. Of 6125 individuals (62±10 years; 47% men) who reported information on FH, 1262 (21%) had an FH of premature coronary heart disease. Among these, 104 hard ASCVD events occurred. Crude incidence rates (per 1000 person-years) for hard ASCVD were 4.4 for CAC, 0 (n=574; 46% of the sample); 8.8 for CAC, 1 to 99 (n=368); 14.9 for CAC, 100 to 399 (n=178); and 20.8 for CAC, ≥400 (n=142). Relative to CAC=0, adjusted hard ASCVD hazard ratios for each CAC category among persons with an FH were 1.64 (95% confidence interval, 0.94-2.87), 2.45 (1.31-4.58), and 2.80 (1.44-5.43), respectively. However, there was no increased adjusted hazard for hard ASCVD in high versus low CIMT categories. In participants with an FH of premature coronary heart disease, CAC improved discrimination of hard ASCVD events (P<0.001). However, CIMT did not discriminate ASCVD (P=0.70).

CONCLUSIONS

Nearly half of individuals reporting FH have zero CAC and may receive less net benefit from aspirin or statin therapy. Among persons with an FH, CAC is a robust marker of absolute and relative risk of ASCVD, whereas CIMT is not.

Multilevel analysis of ADHD, anxiety and depression symptoms aggregation in families

A strong genetic role in the etiology of attention-deficit hyperactivity disorder (ADHD) has been demonstrated by several studies using different methodologies. Shortcomings of genetic studies often include the lack of golden standard practices for diagnosis for ADHD, the use of categorical instead of a dimensional approach, and the disregard for assortative mating phenomenon in parents. The current study aimed to overcome these shortcomings and analyze data through a novel statistical approach, using multilevel analyses with Bayesian procedures and a specific mathematical model, which takes into account data with an elevated number of zero responses (expected in samples with few or no ADHD symptoms). Correlations of parental clinical variables (ADHD, anxiety and depression) to offspring psychopathology may vary according to gender and type of symptoms. We aimed to investigate how those variables interact within each other. One hundred families, comprising a proband child or adolescent with ADHD or a typically developing child or adolescent were included and all family members (both biological parents, the proband child or adolescent and their sibling) were examined through semi-structured interviews using DSM-IV criteria. Results indicated that: (a) maternal clinical variables (ADHD, anxiety and depression) were more correlated with offspring variables than paternal ones; (b) maternal inattention (but not hyperactivity) was correlated with both inattention and hyperactivity in the offspring; (c) maternal anxiety was correlated with offspring inattention; on the other hand, maternal inattention was correlated with anxiety in the offspring. Although a family study design limits the possibility of revealing causality and cannot disentangle genetic and environmental factors, our findings suggest that ADHD, anxiety and depression are variables that correlate in families and should be addressed together. Maternal variables significantly correlated with offspring variables, but the paternal variables did not.

Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the Tehran eye study

Purpose:

The purpose was to determine the familial aggregation of the total, against-the-rule (ATR), with-the-rule (WTR), and oblique astigmatism by conditional and marginal models in the Tehran Eye Study.

Materials and Methods:

Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to −0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20–70° and 110–160°. The familial aggregation was investigated with a conditional model (quadratic exponential) and marginal model (alternating logistic regression) after controlling for confounders.

Results:

Using the conditional model, the conditional familial aggregation odds ratios (OR) (95% confidence interval) for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43–1.72), 1.91 (1.65–2.20), 2.00 (1.70–2.30), and 1.86 (1.37–2.54), respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13–1.63) and 1.54 (1.13–2.11), respectively; WTR 1.53 (1.06–2.20) and 1.94 (1.21–3.13) and; ATR 2.13 (1.01–4.50) and 2.23 (1.52-3.30). The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25–7.20).

Conclusion:

The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.

The risk of type 2 diabetes in men is synergistically affected by parental history of diabetes and overweight

Interactions between genetic- and lifestyle factors may be of specific importance for the development of type 2 diabetes. Only a few earlier studies have evaluated interaction effects for the combination of family history of diabetes and presence of risk factors related to lifestyle. We explored whether 60-year-old men and women from Stockholm with a parental history of diabetes are more susceptible than their counterparts without a parental history of diabetes to the negative influence from physical inactivity, overweight or smoking regarding risk of developing type 2 diabetes. The study comprised 4232 participants of which 205 men and 113 women had diabetes (the vast majority type 2 diabetes considering the age of study participants) and 224 men and 115 women had prediabetes (fasting glucose 6.1–6.9 mmol/l). Prevalence odds ratios (OR) with 95% confidence intervals (95% CI) were calculated using logistic regression. Biologic interaction was analyzed using a Synergy index (S) score. The crude OR for type 2 diabetes associated with a parental history of diabetes was 2.4 (95% CI 1.7–3.5) in men and 1.4 (95% CI 0.9–2.3) in women. Adjustments for overweight, physical inactivity and current smoking had minimal effects on the association observed in men whereas in women it attenuated results. In men, but not in women, a significant interaction effect that synergistically increases the risk of developing type 2 diabetes was observed for the combination of BMI>30 and a parental history of diabetes, S 2.4 (95% CI 1.1–5.1). No signs of interactions were noted for a parental history of diabetes combined with physical inactivity and smoking, respectively. In conclusion, obesity in combination with presence of a parental history of diabetes may be particularly hazardous in men as these two factors were observed to synergistically increase the risk of developing type 2 diabetes in men.

Familial aggregation and heritability of insomnia in a community-based study

BACKGROUND

Emerging data suggested a significant familial aggregation of insomnia. We aimed to clarify the familial aggregation and heritability of insomnia disorder by using structural clinical interviews for the ascertainment of insomnia and psychiatric disorders in a community-based sample.

METHODS

Seventy-five adolescents with insomnia and their 180 first degree relatives, together with 141 age- and sex-matched non-insomnia controls and their 382 first degree relatives, were recruited. Each subject underwent a structured clinical interview and completed a series of psychometric inventories. The rates of insomnia disorder among the first degree relatives were employed to analyze familial aggregation. Heritability of insomnia was analyzed by SOLAR program as based on father-mother-offspring trios.

RESULTS

Our study confirmed a significant familial aggregation of insomnia with a first degree relatives' recurrence risk of 2.33 for current insomnia and 2.82 for lifetime insomnia, respectively. The heritability±SE of current and lifetime insomnia disorder was 0.48±0.13 and 0.61±0.11 (p<0.001), respectively, which were higher than insomnia symptoms as estimated by the Insomnia Severity Inventory (h(2)±SE=0.27±0.09) and the Pittsburgh Sleep Quality Index (h(2)±SE=0.30±0.11). After exclusion of comorbid psychiatric disorders, the heritability for current and lifetime primary insomnia was 0.45±0.17 (p=0.007) and 0.58±0.21 (p=0.004), respectively.

CONCLUSIONS

Our study demonstrates a significant familial aggregation with a high heritability of insomnia disorder. The strong heritability of insomnia persists despite the exclusion of psychiatric disorders. Further molecular genetic investigation of insomnia is indicated.

Family history of cancer and non-malignant diseases and risk of childhood acute lymphoblastic leukemia: a Children's Oncology Group Study

BACKGROUND

Studies of family history of cancer and non-malignant diseases in childhood acute lymphoblastic leukemia (ALL) show inconsistent findings. Most studies show no increased risk with family history of cancer. Non-malignant diseases such as allergic diseases, autoimmune diseases, birth defects and thyroid diseases have been reported to be associated with ALL.

METHODS

We conducted a case-control study of family history of cancer and selected non-malignant conditions (allergic diseases, autoimmune diseases, birth defects, and thyroid diseases). ALL cases were obtained from Children's Cancer Group institutions from January 1989 to June 1993. Controls were recruited via random digit dialing. Family history for first degree relatives and grandparents of ALL cases and controls was collected by structured telephone questionnaires. Conditional logistical regression was used to calculate odds ratios adjusting for potential confounders.

RESULTS

We found a borderline association of ALL and having a family member with a history of cancer in cases (n=1842) compared to controls (n=1986) (OR=0.98, 95%CI=0.93, 1.00) and an inverse association for esophageal cancer based on small numbers. Family history of food and drug allergies demonstrated a modestly reduced risk (OR=0.83, 95%CI=0.73, 0.95) as did family history of rheumatoid arthritis (OR=0.79, 95%CI=0.65, 0.96). There were no associations with family history of any autoimmune diseases, immunodeficiencies, birth defects, thyroid diseases and risk of childhood ALL.

CONCLUSIONS

These results show no association of overall family history of cancer with childhood ALL, while providing additional evidence for an inverse association with family history of allergic disease. Two potentially new associations of ALL with family history of esophageal cancer and rheumatoid arthritis require confirmation in other studies and validation with medical records.

Family history of thyroid cancer and the risk of differentiated thyroid cancer in French polynesia

BACKGROUND

Differentiated thyroid carcinoma is considered to be the nonhereditary cancer for which familial inheritance is the highest. To date, no familial aggregation analysis of this cancer has been performed in Maohi populations, which exhibit a very high incidence rate. Therefore, we evaluate the risk of differentiated thyroid cancer associated with a family history of thyroid cancer in natives of French Polynesia.

METHODS

We investigated thyroid cancer incidence in the first-degree relatives of 225 cases of differentiated thyroid carcinomas diagnosed between 1979 and 2004 in patients born in French Polynesia, and 368 randomly selected population controls matched for sex and age, born and residing in French Polynesia. All but five thyroid cancers declared among relatives were validated.

RESULTS

Twenty-four cases declared a family history of thyroid cancer, when compared with 11 controls. Individuals with an affected first-degree relative had a 4.5-fold (95% confidence interval [CI], 1.9-10.6) increased risk of differentiated thyroid cancer. This odds ratio (OR) was not significantly higher when a male first-degree relative was affected (OR, 10.0; 95% CI, 1.3-74.8) compared with a female (OR, 4.0; 95% CI, 1.5-10.3) and was not different for patients who had a nonaggressive thyroid microcarcinoma (OR, 3.5; 95% CI, 0.6-16.4) than those who had a larger cancer (OR, 6.0; 95% CI, 1.8-20.5). This OR was borderline significantly (p, 0.07) higher in Maohis (OR, 11.0; 95% CI, 2.4-48.8) than in individuals of mixed origin (OR, 2.1; 95% CI, 0.8-5.9).

CONCLUSION

Our study shows that the familial inheritance of differentiated thyroid cancer is particularly high in Maohi populations.

Family history and lung cancer risk: international multicentre case-control study in Eastern and Central Europe and meta-analyses

Lung cancer is the most common neoplastic disease in Eastern and Central Europe. The role of hereditary factors in lung carcinogenesis is not fully understood. Family history (FH) of lung cancer and other tobacco-related cancers might be a strong predictor of the lung cancer risk. We investigated family history of cancer among first-degree relatives of 2,861 patients with lung cancer and 3,118 controls from the Czech Republic, Hungary, Poland, Romania, Russia, Slovakia, and United Kingdom within the IARC Multicenter Case-Control Study. Odds ratios (ORs) and 95% CI were calculated using logistic regression, adjusting for age, gender, study center, education, tobacco smoking, and number of first-degree relatives. In addition, we conducted a meta-analysis of 41 studies on FH of cancer and lung cancer risk. Positive FH of lung cancer increased risk of lung cancer with OR of 1.63 (95%CI: 1.31-2.01), and having two or more affected relatives with lung cancer further increased the risk of lung cancer with OR 3.60 (95%CI: 1.56-8.31). Among subjects aged less than 50, the OR for FH of lung cancer was 2.08 (95%CI: 1.18-3.63). The associations were generally stronger for squamous cell carcinoma and large cell carcinoma subtypes. Heterogeneity in results was not found with respect to smoking status and gender. A significant association was not observed for FH of other smoking-related tumors. The results of meta-analysis were consistent with that of our study with regard to young onset, non-smokers and histology. FH of lung cancer is a predictor of an increased risk of lung cancer, especially in subjects aged less than 50.

Familial melanoma: a meta-analysis and estimates of attributable fraction

Melanoma commonly clusters in families, and the recent identification of numerous genotypes predicting higher risks of melanoma has led to the widespread perception that this cancer is predominantly a genetic disease. We conducted a systematic review of the literature and meta-analysis to quantify the contribution of familial factors to melanoma, estimated by the population attributable fraction (PAF). Eligible studies were those that permitted quantitative assessment of the association between histologically confirmed melanoma and family history of the disease; we identified 22 such studies using citation databases, followed by manual review of retrieved references. We calculated summary RRs using weighted averages of the log RR, taking into account random effects, and used these to estimate the PAF. Overall, family history was associated with a significant 2-fold increased risk of melanoma (odds ratio, 2.06; 95% confidence interval, 1.72-2.45); however, there was significant heterogeneity (P = 0.01). The pooled estimate for population-based studies (n = 11) was 2.03 (1.70-2.43), and 2.51 (1.55-4.07) for clinic/hospital-based studies (n = 11), both with significant heterogeneity (P = 0.049 and P = 0.013, respectively). Two studies used record linkage to verify family history in relatives; the pooled risk estimate from these two studies was 2.52 (2.11-3.00) with no evidence of heterogeneity (P = 0.258). Estimates of PAF associated with a positive family history ranged from 0.007 for Northern Europe to 0.064 for Australia (0.040 for all regions combined). Our findings suggest that only a small percentage of melanoma cases (always <7%) are attributable to familial risk; the majority of melanomas are presumably attributable to other factors.

Coherence and completeness of population-based family cancer reports

BACKGROUND

Although family history of cancer is widely ascertained in research and clinical care, little is known about assessment methods, accuracy, or other quality measures. Given its widespread use in cancer screening and surveillance, better information is needed about the clarity and accuracy of family history information reported in the general population.

METHODS

This telephone survey in Connecticut examined coherence and completeness of reports from 1,019 respondents about 20,504 biological relatives.

RESULTS

Of 2,657 cancer reports, 97.7% were judged consistent with malignancy (versus benign or indeterminate conditions); 79% were site specific, 10.1% had unspecified cancer sites, and 8.6% had "ill-defined" sites. Only 6.1% of relatives had unknown histories. Unknown histories and ambiguous sites were significantly higher for second-degree relatives. The adjusted percentage of first-degree relative reports with ambiguous sites increased with decreasing education and African-American race of survey respondents, and with deceased vital status of relatives. Ambiguous second-degree relative reports were also associated with deceased vital status and with male gender of respondents.

CONCLUSIONS

These findings suggest that family history of cancer reports from the general population are generally complete and coherent.

IMPACT

Strategies are needed to improve site specificity and thus maximize the utility of such information in primary care settings.

Methods for assessing familial aggregation: family history measures and confounding in the standard cohort, reconstructed cohort and case-control designs

OBJECTIVES

To test whether case-control-based familial aggregation studies produce estimates of risk to relatives that are inherently biased or confounded by age and family size, and to compare case-control-derived estimates with those from the reconstructed cohort method. In addition, we test if the definition of family history affects the accuracy of results obtained from either design. We use simulated data, which allows us to know the true data origin.

METHODS

We simulated populations of three generation families. Both a dominant genetic disease and a non-genetic disease were present in the population. We compared the effect estimates from different measures of family history with those derived from the actual genetic cause of disease.

RESULTS

Effect estimates from family history measures that used multiple family members were more accurate than those derived from measures based on a single relative. Neither family size nor age of family members defining family history were confounders in the case-control design.

CONCLUSION

The case-control and reconstructed cohort designs are equally valid in assessing familial aggregation of disease.

Familial aggregation of Parkinson's disease: a meta-analysis

We sought to determine the relative risk (RR) of Parkinson's disease (PD) for having a first-degree relative with PD versus having no first-degree relative with PD. Studies of familial aggregation of PD were identified by searching Medline and other sources. From each study, RRs were extracted or calculated based on the published data. Studies were categorized according to methodological characteristics, as well as by first-degree relationship type and age at PD onset restrictions. Meta-analyses and meta-regressions were based on random effect models. Twenty-nine studies of familial aggregation of PD were identified with results for first-degree relatives. The best estimate of the RR of PD for having a first-degree relative with PD was 2.9 (95% CI: 2.2, 3.8; P = 2.2 E-14), based on the studies with the most rigorous methods. The RR for sibling pairs was 4.4 (95% CI: 3.1, 6.1; P < 1.0 E-30), while for child-parent pairs it was 2.7 (95% CI: 2.0, 3.7; P = 3.6 E-10). The RR for early onset PD was 4.7 (95% CI: 3.2, 6.8; P = 6.7 E-16), while for late onset PD it was 2.7 (95% CI: 1.9, 3.9; P = 1.8 E-8). Inclusion of methodologically less rigorous investigations tended to increase the RR estimates. Summary RRs were clearly elevated above one for all study methods, all first-degree relationship types, and all age at onset categories. Familial aggregation of PD is strong and unlikely to be due to chance or to deficiencies in study methodology.

Risk of bladder cancer associated with family history of cancer: do low-penetrance polymorphisms account for the increase in risk?

The relationship between family history of cancer in first-degree relatives and risk of bladder cancer was examined in the Spanish Bladder Cancer Study. Information on family history of cancer was obtained for 1,158 newly diagnosed bladder cancer cases and 1,244 controls included in 18 hospitals between 1998 and 2001. A total of 464 (40.1%) cases and 436 (35.1%) controls reported a family history of cancer in >/=1 relative [odds ratio (OR), 1.32; 95% confidence interval (95% CI), 1.11-1.59]; the OR was 1.23 (95% CI, 1.01-1.50) among those with only one relative affected and 1.67 (95% CI, 1.23-2.29) among those with >/=2 affected relatives (P(trend) = 0.0004). A greater risk of bladder cancer was observed among those diagnosed at age </=45 years (OR, 2.67; 95% CI, 1.10-6.50) compared with those diagnosed over age 45 years (OR, 1.27; 95% CI, 1.06-1.52). The OR of bladder cancer among subjects reporting a family history of cancer of the bladder was 2.34 (95% CI, 0.95-5.77). Statistically significant associations emerged between bladder cancer risk and family history of cancer of the esophagus, lung, prostate, and brain. The OR of bladder cancer for those reporting family history of bladder cancer was 4.76 (95% CI, 1.25-18.09) among NAT2-slow acetylators and 1.17 (95% CI, 0.17-7.86) among NAT2-rapid/intermediate acetylators (P(interaction) = 0.609). Among individuals with GSTM1 null and present genotypes, the corresponding ORs were 2.91 (95% CI, 0.44-19.09) and 4.21 (95% CI, 1.26-14.14), respectively (P(interaction) = 0.712). Limitations of our study are small sample size in subgroup analyses, reliability of family history data, and possible residual confounding by shared environmental exposures. Overall, our findings support the hypothesis that genetic factors play a role in bladder cancer etiology. Whether these correspond to low-penetrance cancer-predisposing polymorphisms acting together and/or interacting with environmental factors warrants further research.

Importance of Family History in Lifestyle Management

Families affect the health of their members by transmitting genetic predisposition to wellness and illness. Families also model and teach health beliefs, attitudes, and behaviors. Eliciting an individual's family history can identify potential genetic vulnerabilities to disease and lifestyle influences. This review explores the implications of family history for patient education about lifestyle. Family history is particularly useful for helping health care providers be effective with individuals who have strong family patterns of atherosclerotic cardiovascular disease, major risk factors (dyslipidemia, hypertension, diabetes, and tobacco use), and related factors (obesity, poor nutrition, physical inactivity, and alcohol excess). Gathering and recording family history information can be problematic, even with an electronic medical record (EMR). The genogram (expanded genetic pedigree) is an efficient way to record and display family history data. Family history data in genogram format can be used as a versatile patient education tool. Despite its clinical utility, the genogram has been used more for teaching than for patient care. Thus far, the genogram has not been integrated into the EMR. Adding relevant cultural information to the conventional genogram might increase its utility for helping health care providers encourage lifestyle changes that promote wellness and prevent disease, disability, and premature death in ethnically diverse populations.

Familial aggregation of ischemic stroke in young women: the Stroke Prevention in Young Women Study

BACKGROUND AND PURPOSE

Stroke occurs infrequently in young adults. While a familial basis for older onset stroke is well established, the extent of familial clustering in young-onset stroke is unknown. To address this issue, we compared the frequency of stroke in relatives of stroke cases to that in relatives of controls across different ages and by stroke subtype.

METHODS

Through a population-based case-control study of stroke, we identified 487 women aged 15-49 years with ischemic stroke and 615 women without stroke matched by age and geographic region. Family history of stroke was collected for 5,749 relatives (parents and siblings) of case and control probands by standardized interview.

RESULTS

Strokes were reported in 149 relatives of case patients and 119 relatives of controls. Siblings of stroke case patients had more than four times the risk of stroke compared to siblings of controls (OR, 4.17; 95% CI, 1.9-8.8) and mothers of stroke case patients had twice the risk of stroke compared to mothers of control subjects (OR, 2.02; 95% CI, 1.4-3.0). The association between stroke in probands and family history of stroke was strongest among women aged 15-24 years (OR, 2.5; 95% CI, 0.4-15.1), and diminished with increasing proband age (OR, 1.6; 95% CI, 0.8-3.3 among women 25-34 years and OR, 1.5; 95% CI, 1.1-1.9 among women 35-49 years; P<0.0001 for trend).

CONCLUSIONS

We conclude that young-onset stroke aggregates in families and that the magnitude of aggregation increases with decreasing proband age.

Family history and risk of lung cancer: age-at-diagnosis in cases and first-degree relatives

To investigate the little known risk of lung cancer at an early age when a first-degree relative has had such a diagnosis, 579 incident cases and 1157 population controls were studied in Liverpool between 1998 and 2004 using standardised questionnaires covering demography and lifestyle. A history of lung cancer in first-degree relatives was associated with a significantly increased risk in the proband where in both individuals the cancers were diagnosed before the age of 60 years (odds ratio (OR)=4.89; 95% confidence interval (CI): 1.47–16.25). A significantly elevated risk of lung cancer was also observed in association with a relative affected before the age of 60 years, regardless of age-at-onset of the disease (OR=2.08; 95% CI: 1.20–3.59). This finding is strongly consistent with a genetic component in early-onset lung cancer risk.

Case-control and case-only designs with genotype and family history data: estimating relative risk, residual familial aggregation, and cumulative risk

In case-control studies of inherited diseases, participating subjects (probands) are often interviewed to collect detailed data about disease history and age-at-onset information in their family members. Genotype data are typically collected from the probands, but not from their relatives. In this article, we introduce an approach that combines case-control analysis of data on the probands with kin-cohort analysis of disease history data on relatives. Assuming a marginally specified multivariate survival model for joint risk of disease among family members, we describe methods for estimating relative risk, cumulative risk, and residual familial aggregation. We also describe a variation of the methodology that can be used for kin-cohort analysis of the family history data from a sample of genotyped cases only. We perform simulation studies to assess performance of the proposed methodologies with correct and mis-specified models for familial aggregation. We illustrate the proposed methodologies by estimating the risk of breast cancer from BRCA1/2 mutations using data from the Washington Ashkenazi Study.

Measures of familial aggregation depend on definition of family history: meta-analysis for colorectal cancer

OBJECTIVE

Familial aggregation, a primary theme in genetic epidemiology, can be estimated from family studies based on an index person. The excess risk due to the presence of affected family members can be classified according to whether disease in the relatives is considered a risk factor for the index person (type I relative risk) or whether the disease status of the index person is considered a risk factor for the relatives (type II relative risk).

STUDY DESIGN AND SETTING

A meta-analysis of published colorectal cancer studies reporting a measure of familial association was performed and application of multilevel linear regression to model age-specific relative risks presented.

RESULTS

The pooled type I relative risk of colorectal cancer given any affected first-degree relative (based on 20 studies) was 2.26 (95% confidence interval CI = 1.86, 2.73) and decreased with the age of the consultand. The pooled type II estimate (based on seven studies) was 2.81 (95% CI = 2.05, 3.85).

CONCLUSION

Type I relative risks are useful in clinical counseling settings when a consultand wants to know his/her disease risk given his or her family history. Type II relative risks can be used to quantify the risk of disease to relatives of an affected individual and then identify subjects eligible for screening.

Family history of coronary heart disease: evidence-based applications

Clinicians sometimes consider family history of CHD when evaluating CHD risk and deciding whether to prescribe a lipid medication. Most clinicians who take family history of CHD into account do so by categorically adjusting the aggressiveness of patient education and preventive medication recommendations (eg, from a low-key informational mode to a more direct influential or persuasive mode). Quantitative methods exist for taking into account any family history of CHD in parents and siblings, when estimating an individual's 10-year risk for a CHD event; at present, these methods are not readily available. For those individuals who have a positive family history of CHD, using family history-adjusted risk estimates could help clinicians more accurately target high-risk individuals who are the most appropriate candidates for therapeutic lifestyle changes and dyslipidemia drug therapy. Electronic health records (EHR) that now include CHD risk estimation as a decision support feature exclude family history from the calculation. Unless family CHD history is included in EHR decision support modules, family history of CHD will be increasingly discounted or ignored, as clinicians come to rely more and more on computerized decision support aids.

Racial differences in the familial aggregation of breast cancer and other female cancers

Although breast cancer familial aggregation has been studied in Caucasians, information for African-Americans is scant. We used family cancer history from the Women's Contraceptive and Reproductive Experiences study to assess the aggregation of breast and gynecological cancers in African-American and Caucasian families. Information was available on 41,825 first and second-degree relatives of Caucasian and 28,956 relatives of African-American participants. We used a cohort approach in which the relative's cancer status was the outcome in unconditional logistic regression and adjusted for correlated data using generalized estimating equations. Race-specific models included a family history indicator, the relative's age, and type. Relative risk (RR) estimates for breast cancer were highest for first-degree relatives, and the overall RR for breast cancer among case relatives was 1.96 (95% CI = 1.68-2.30) for Caucasian and 1.78 (95% CI = 1.41-2.25) for African-Americans. The effect of CARE participants' reference age on their relatives' breast cancer risk was greatest among first-degree relatives of African-American patients with RRs (95% CI) for ages <45 and > or =45 of 2.97 (1.86-4.74) and 1.48 (1.14-1.92), respectively. Among Caucasians, first-degree relatives of case subjects were at greater risk for ovarian cancer, particularly relatives younger than 45 years (RR (95% CI) = 2.06 (1.02-4.12)), whereas African-American first-degree relatives of case subjects were at increased cervical cancer risk (RR (95% CI) = 2.17 (1.22-3.85). In conclusion, these racially distinct aggregation patterns may reflect different modes of inheritance and/or environmental factors that impact cancer risk.

Meningioma and schwannoma risk in adults in relation to family history of cancer

Relatively little is known about factors that contribute to the development of meningioma and vestibular schwannoma, two intracranial nervous system tumors. We evaluated the risk of these tumors in relation to family history of malignant or benign tumors. Incident cases of meningioma (n = 197) or schwannoma (n = 96) were identified at three U. S. referral hospitals between June 1994 and August 1998. Controls (n = 799) admitted to the same hospitals for nonmalignant conditions were matched to cases on age, sex, race/ethnicity, hospital, and proximity of residence to hospital. We found that risk of meningioma was increased among persons reporting a family history of a benign brain tumor (odds ratio [OR], 4.5; 95% confidence interval [CI], 1.0-21.0; n = 5) or melanoma (OR, 4.2; 95% CI, 1.2-15.0; n 5). A family history of breast cancer was associated with an elevated meningioma risk among participants aged 18 to 49 years (OR, 3.9; 95% CI, 1.4-11.0; n = 8) but a reduced risk among older respondents (OR, 0.2; 95% CI, 0.1-0.7; n = 3). Family history of cancer did not differ between schwannoma cases and controls, although the statistical power to detect associations was limited. Some relative risk estimates were based on a small number of observations and may have arisen by chance. Inheritance of predisposing genes, shared environmental factors, or both within families with a history of benign brain tumors, melanoma, or possibly breast cancer may be related to altered meningioma risk.

Bias

The concept of bias is the lack of internal validity or incorrect assessment of the association between an exposure and an effect in the target population in which the statistic estimated has an expectation that does not equal the true value. Biases can be classified by the research stage in which they occur or by the direction of change in a estimate. The most important biases are those produced in the definition and selection of the study population, data collection, and the association between different determinants of an effect in the population. A definition of the most common biases occurring in these stages is given.

Testicular, Other Genital, and Breast Cancers in First-Degree Relatives of Testicular Cancer Patients and Controls

Previous studies showed an increased prevalence of testicular cancer among fathers and brothers of testicular cancer patients. We examined whether testicular, other genital, and breast cancers aggregate in parents and siblings of testicular cancer patients in a population-based case-control study, including males, ages 15 to 69 years at diagnosis, with primary malignant tumors of the testes or extragonadal germ cell tumors. Controls were ascertained through the mandatory registries of residents and frequency matched to the cases by age and region of residence. In a face-to-face interview, 269 cases and 797 controls provided health-related information on parents and siblings. We calculated odds ratios (OR) and corresponding 95% confidence intervals (95% CI) based on the generalized estimating equations technique, adjusting for the matching variables and relatives' age. Three (1.1%) fathers and eight (3.2%) brothers of cases were affected with testicular cancer compared with four (0.5%) fathers and two (0.2%) brothers of controls. The OR (95% CI) of familial testicular cancer was 6.6 (2.35-18.77). Only nonseminoma patients had fathers with testicular cancer, whereas the affected brothers were all related to seminoma patients. Overall, we found an increased risk for genital other than testicular cancers (OR 2.5, 95% CI 1.43-4.43). For breast cancer, we detected an increased risk in sisters (OR 9.5, 95% CI 2.01-45.16, adjusted for age of study participant and age of sister) but not in mothers. Our findings support the hypothesis that testicular and other genital cancers have a common familial component that may be due to genetic and shared exogenous factors such as estrogen exposure during fetal development.

Family history of ischemic heart disease and risk of acute myocardial infarction

BACKGROUND

Several aspects of the relation between family history of ischemic heart disease (IHD) and risk of acute myocardial infarction (AMI) need further quantification.

METHODS

A case-control study was conducted in Italy in 1995-1999 on 378 men and 129 women with a first nonfatal AMI, and 297 male and 181 female controls in a hospital for selected acute conditions. Odds ratios (OR) of AMI according to family history of IHD were estimated using unconditional logistic regression, adjusting for other AMI risk factors and family size.

RESULTS

The overall OR for those having > or =1 first-degree relatives with IHD was 2.1, and 3.8 for > or =2 relatives. The OR for those with an affected parent or sibling were similar. The OR were also similar across strata of sex, age at diagnosis of the proband or the relative, and selected AMI risk factors, which were risk factors also in those with a positive family history.

CONCLUSIONS

Family history of IHD is an independent risk factor for AMI, and intervention on modifiable risk factors may be beneficial also in those with a family history of the disease.

Aggregation of stomach cancer history in parents and offspring in comparison with other sites

BACKGROUND

The aim of this study is to evaluate the magnitude of the aggregation of a stomach cancer history in parents and their offspring in comparison with that of a history at other sites.

METHODS

We used the baseline data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study), which was initiated during 1988-1990 in Japan. Association of the cancer history of the subjects' parents with that of the subjects themselves and any of the subjects' siblings was evaluated with odds ratios (OR) by the crude and generalized estimating equations (GEE) technique for four sites: stomach, colorectum, liver, and lung/bronchus.

RESULTS

The aggregation of a history of stomach cancer between parents and their offspring was evident with significant OR >2.5. The magnitude of the parent-offspring association of a disease history of the colorectum and liver was found to be greater than that for stomach cancer. Conversely, lung and bronchus cancer failed to demonstrate a significant aggregation.

CONCLUSIONS

The hereditary and environmental influences shared by parents and offspring are likely to play a strong aetiological role in colorectal or liver cancer versus a weaker but still significant role in stomach cancer. In contrast, the aetiological role of familial predisposition to lung cancer was indeterminate, which suggests a predominant role of non-familial factors in the development of lung cancer.

Regression methods for assessing familial aggregation of disease

This paper reviews methods for assessing familial aggregation of disease based on simple logistic regression models. Studies are based on a case-control sampling design, where the disease status of the first degree relatives of both cases and controls are obtained. Both 'proband predictive' and 'family predictive' models are discussed, and an example is given using a case-control sample from a lung cancer study in non-smokers. The methods are extended to characterize co-aggregation of two disorders, that is, presence of one disorder in the proband increases the risk of a second disorder in the relative. An example involving eating disorders and depression is given.

Reproductive factors and familial predisposition for breast cancer by age 50 years. A case-control-family study for assessing main effects and possible gene-environment interaction

BACKGROUND

The effect of environmental/lifestyle factors on breast cancer risk may be modified by genetic predisposition.

METHODS

In a population-based case-control-family study performed in Germany including 706 cases by age 50 years, 1381 population, and 252 sister controls, we investigated main effects for environmental/lifestyle factors and genetic susceptibility and gene-environment interaction (G x E). Different surrogate measures for genetic predisposition using pedigree information were used: first-degree family history of breast or ovarian cancer; and gene carrier probability using a genetic model based on rare dominant genes. Possible G x E interaction was studied by (1) logistic regression using cases and population controls including an interaction term; (2) comparing results using sister controls and population controls; (3) case-only analysis with logistic regression and (4) a mixture logistic model.

RESULTS

Familial predisposition showed the strongest main effect and the estimated gene carrier probability gave the best fit. High parity and longer duration of breastfeeding reduced breast cancer risk significantly, a history of abortions increased risk and age at menarche showed no significant effect. We found significant G x E interaction between parity and genetic susceptibility using different surrogate measures. In women most likely to have a high genetic susceptibility, high parity was less protective. Later age at menarche was protective in women with a positive family history. No evidence for G x E interaction was found for breastfeeding and abortion.

CONCLUSIONS

These findings corroborate results from other studies and provide further evidence that the magnitude of protection from parity is reduced in women most likely to have a genetic risk in spite of the limitations of using surrogate genetic measures.

Family history and risk of subarachnoid hemorrhage: a case-control study in Nagoya, Japan

BACKGROUND AND PURPOSE

We sought to examine the relation between a family history of subarachnoid hemorrhage (SAH) and the risk of SAH by using a case-control study.

METHODS

Case subjects consisted of a consecutive series of 195 patients with spontaneous SAH, aged 30 to 79 years, with aneurysms confirmed by angiography and/or CT scan. Hospital and community control subjects were identified and matched to each case by sex and age (+/-2 years). Multiple conditional logistic regression was used to calculate the odds ratio (OR) and 95% interval (CI) adjusted for potential confounders.

RESULTS

Having a family member with SAH was significantly associated with an increased risk of SAH (OR, 4.0, 95% CI, 2.0 to 8.0), after adjusting for potential confounders. The risk for a positive family history of SAH was similar for men and women and was inversely related to the SAH patient's age. A maternal positive SAH history (OR, 5.4; 95% CI, 1.8 to 16.0) posed a much greater risk than a paternal positive history (OR, 3.2, 95% CI, 1.1 to 13.4).

CONCLUSIONS

A positive family history of SAH was significantly and strongly associated with the risk of SAH. To prevent the onset of SAH at a younger age, much more attention should be given to individuals with any family member (first-degree relatives) suffering SAH episodes.

Bias in self-reported family history and relationship to glaucoma: the Blue Mountains Eye Study

PURPOSE

To examine bias in the relationship between self-reported family history of glaucoma and its relationship to the prevalence of glaucoma and ocular hypertension.

METHODS

In a cross-sectional population-based study of 3654 Australians aged 49-97, participants were asked whether any first-degree relatives had been diagnosed with glaucoma. Open-angle glaucoma was diagnosed from matching optic disc and typical visual field changes, after gonioscopy. Ocular hypertension (OH) was diagnosed from elevated intraocular pressure (IOP) in subjects without glaucoma.

RESULTS

Glaucoma was present in 3.0% and ocular hypertension in 5.2% of subjects. A parent or sibling was reported to have glaucoma by 8.6%, including 10.5% of women and 5.9% of men. A positive family history was reported more frequently in parents (6.4%) than siblings (2.6%). Glaucoma was reported more frequently to affect mothers (5.0%) and sisters (1.6%) than fathers (1.5%) and brothers (1.2%). A first-degree family history was given by 15.7% of subjects with glaucoma compared to 8.3% of controls, odds ratio (OR) 3.2 (95% CI 1.8-5.6), after adjusting for glaucoma risk factors, including IOP. The association had a similar magnitude for a family history in parents and siblings. Although recall bias was evident from the finding of increased odds (OR 4.2) among previously diagnosed cases, the relationship with family history also persisted in newly-diagnosed cases (OR 2.4). A slightly stronger relationship was found between OH and glaucoma family history, OR 3.9 (95% CI 2.6-5.7), after adjusting for confounders, but was also strongly influenced by recall bias.

CONCLUSIONS

Although a positive family history of glaucoma may help to identify those at risk, it is subject to recall, selection and survival bias as well as community under-diagnosis of glaucoma and will most likely substantially underestimate the genetic influence.

Family history of coronary heart disease, a strong risk factor for myocardial infarction interacting with other cardiovascular risk factors: results from the Stockholm Heart Epidemiology Program (SHEEP)

We explored the relation between family history of coronary heart disease and the risk of myocardial infarction in a case-control study of subjects, 45 to 70 years of age, living in Stockholm, Sweden. Our cases comprised 1091 male and 531 female first-time acute myocardial infarction patients who had survived at least 28 days after their infarction. Referents were randomly selected from the population from which the cases were derived. The adjusted odds ratio (OR) of myocardial infarction was 2.0 (95% confidence interval [CI] = 1.6-2.6) for men reporting > or = 1 affected parent or sibling, compared with men with no family history of coronary heart disease, and 3.4 (95% CI = 2.1-5.9) for those reporting > or = 2 affected parents or siblings. The corresponding OR for women were 2.1 (95% CI = 1.5-3.0) and 4.4 (95% CI = 2.4-8.1). We found evidence for synergistic interactions in women exposed to family history of coronary heart disease in combination with current smoking and with a high quotient between low-density lipoprotein and high-density lipoprotein cholesterol (>4.0), respectively, which yielded adjusted synergy index scores of 2.9 (95% CI = 1.2-7.2) and 3.8 (95% CI = 1.5-9.7), respectively. Similarly, in men we found evidence for interaction for the co-exposure of family history of coronary heart disease and diabetes mellitus. Our study shows that family history of coronary heart disease is not only a strong risk factor for myocardial infarction in both sexes, but that its effect is synergistic with other cardiovascular risk factors as well.

Multivariate logistic regression for familial aggregation of two disorders. I. Development of models and methods

The question of whether two disorders cluster together, or coaggregate, within families often arises. This paper considers how to analyze familial aggregation of two disorders and presents two multivariate logistic regression methods that model both disorder outcomes simultaneously. The first, a proband predictive model, predicts a relative's outcomes (the presence or absence of each of the two disorders) by using the proband's disorder status. The second, a family predictive model derived from the quadratic exponential model, predicts a family member's outcomes by using all of the remaining family members' disorder statuses. The models are more realistic, flexible, and powerful than univariate models. Methods for estimation and testing account for the correlation of outcomes among family members and can be implemented by using commercial software.

Does allergy in parents depend on allergy in their children? Recall bias in parental questioning of atopic diseases. Multicenter Allergy Study Group

BACKGROUND

A positive atopic family history has proved to be one important risk factor for the development of atopic diseases in offspring. However, many epidemiologists are concerned about the accuracy and reliability of data because responses to questionnaires can be biased for many reasons.

OBJECTIVE

The study investigated whether responses of parents questioned about their atopic diseases change depending on the development of atopic symptoms in their children.

METHODS

During a prospective birth cohort study on atopy in children (the Multicenter Allergy Study) parents filled out questionnaires twice within 2 years about their atopic diseases. Differences between the 2 responses were examined by log-linear and logistic regression models depending on the diagnosed atopy status of the study children.

RESULTS

Mothers tended to report more atopic diseases in the second questioning than in the first, indicating a nondifferential misclassification. Fathers were influenced by the development of atopic diseases in their children: they reported significantly more atopic diseases if the child developed atopic illness with atopic dermatitis.

CONCLUSION

In parental questioning about atopic diseases, a recall bias must be considered for the association of atopic family history and atopy in children. Especially in case-control and cross-sectional studies, such misclassifications can result in biased estimates of prognosis and risk factors.

The influence of familial and hereditary factors on the prognosis of breast cancer

BACKGROUND

Family history is a well recognized risk factor for breast cancer, but its impact in terms of breast cancer survival is uncertain. The recent identification of breast cancer predisposing genes has provided new clinical insights in this field.

DESIGN

English literature identified through Medline between 1976 and February 1999 was reviewed including search terms: breast cancer, survival, prognosis, family history, genetics, BRCA1, BRCA2, and related articles.

RESULTS

Publications were divided into three categories. Family history-based studies: eighteen articles were reviewed. Four studies showed a statistically significant better survival in patients with a family history of breast cancer, and two studies demonstrated a significantly worse prognosis in this context. The remaining articles showed no significant difference. LINKAGE STUDIES: Two studies based on linkage to BRCA1 found that overall survival was better in linked families. A third one concluded to a worse outcome in BRCA2-linked tumors. MUTATION-BASED STUDIES: 10 studies looking at the association between germ-line mutations in BRCA1/BRCA2 and clinical outcomes were reviewed. Eight articles reported no significant difference in outcome, whereas two studies showed a worse outcome in patients with mutations.

CONCLUSIONS

Conflicting data exist as to whether the prognosis of familial or hereditary breast cancer differs from that of sporadic cases. Some of the discrepancies may be explained by methodological differences or biases. However, no studies showed a survival advantage for BRCA1 mutation carriers. This seems to indicate that BRCA1-related breast cancer is not associated with a survival advantage, and that in fact, certain BRCA1 germline mutations confer a worse prognosis. However, to adequately answer this question, more efficient molecular tools to identify all the genetic changes responsible for breast cancer predisposition, and large cohort studies to evaluate their clinical consequences, are needed.

Risk of colon cancer associated with a family history of cancer or colorectal polyps: the diet, activity, and reproduction in colon cancer study

The Diet, Activity, and Reproduction in Colon Cancer (DARCC) study is a large, multi-center case-control study of colon cancer. We examined family histories of cancer among first-degree relatives obtained by computer-assisted in-person interviews from the DARCC to study the impact of family histories of several cancers and colorectal polyps on colon cancer risk. We examined familial cancer risks both by treating a family history of polyps or cancer as a covariate in a logistic regression model, and by comparing cancer or polyp incidence among relatives of cases to incidence among relatives of controls in a proportional hazards model. There were few differences between the odds ratios (OR) or confidence intervals (CI) generated from logistic regression models and the hazard rate ratios (HRR) generated from the proportional hazards models. Overall, the OR of colon cancer among subjects with a family history of colorectal cancer was 1.77. There were only minor differences in risk by sex, age and subsite. A family history of colorectal polyps also increased risk by about the same amount as a family history of colorectal cancer. The increased risk associated with a family history of polyps did not appear to decrease with age.