ARTICLE OUTLINE
	Abstract
	Methods
	Results
	Discussion
	Summary & Implications
	Acknowledgements
	References
	Tables

Purpose: We examined the performance of a familial risk assessment
method that stratifies risk for early-onset coronary heart disease by considering the number of relatives with coronary disease, degree of relationship, lineage, and age at diagnosis.

Methods: By using data from the HealthStyles 2003 survey, we assessed
the associations between familial risk and early-onset coronary heart
disease, diabetes, hypercholesterolemia, hypertension, and obesity. By
using area under the curve statistics, we evaluated the discriminatory ability
of various risk assessment models.

Results: Of 4035 respondents, 60% were female and 72% were white, with a mean age of 48.8 years. After adjustment for demographics, strong and moderate risk were significantly associated with approximately a five- and twofold risk of early-onset coronary disease, respectively. After adjustment for demographics and personal history of cardiovascular disease, strong familial risk was also significantly associated with diabetes, hypercholesterolemia, hypertension, and obesity. A risk assessment model that included familial risk, demographics, and personal history of diabetes, hypercholesterolemia, hypertension, and obesity was most optimal with an area under the curve statistic of 87.2%

Conclusions: Familial risk assessment can stratify risk for early-onset coronary heart disease. Several conditions associated with increased familial risk can be prevented. These results have important implications for risk assessment and risk-reducing interventions.
Family history is one of the most important risk factors for early-onset coronary heart disease (CHD). Many studies have found an increase in CHD of approximately two- to threefold given a first-degree relative with CHD,(1-4) and the strength of this association increases as the number of affected first-degree relatives increases(5-10) and with younger ages of CHD onset.(1,5-7,9,11-13) Studies that have investigated family histories of late-onset CHD have also found significant positive associations with CHD, although the relative risks are comparatively smaller.(5,6,9,11-13) Recent studies have demonstrated an increased CHD risk associated with CHD in second-degree relatives,(14,15) and in maternal relatives,(13) although other studies have not found an association between CHD and lineage.(4,7,10,16)

Despite the importance of family history as a CHD risk factor, it is underused in CHD prevention efforts. Many standard risk assessment methods and guidelines underrate the significance of family history.(17-20) If considered at all, assessment is generally limited to early-onset CHD in first-degree relatives only. Many clinicians are also reluctant to assess family history as a disease risk factor because of concerns about the amount of time required to collect the information and their ability to interpret the information accurately.(21-24)

To address these barriers, several national organizations and federal agencies have endorsed the development and use of family history tools, particularly for common chronic diseases, such as CHD, diabetes, and cancer.(25-29) These tools are designed to (1) aid in identifying people with increased disease risk attributable in part to genetic factors; (2) improve early detection and prevention efforts for people with increased familial risk; and (3) facilitate the referral of individuals for genetic evaluation, including genetic counseling and testing. These tools can range from simple guidelines on the collection of family history to complex algorithms that interpret family history data and provide prevention messages tailored to the level of familial risk.

A method of familial risk stratification has been developed that assesses an individual's familial risk for CHD as weak, moderate, or strong based on whether and at what age (i.e., early, late, or unknown) first- and second-degree relatives were diagnosed with CHD. The goal of this study was to determine the prevalence of these familial risk categories for CHD in a cross-sectional study of the U.S. population, and to assess the performance of the stratification method by measuring associations with demographic factors, prevalent CHD, and related medical conditions.

Subjects
Data from the HealthStyles 2003 survey were used for this cross-sectional study. HealthStyles, an annual mail survey of health-related attitudes and behaviors among the U.S. adult population,(30) is a subset of a two-part consumer survey designed and conducted by Synovate, Inc. (Arlington Heights, IL), a marketing firm that annually recruits approximately 600,000 potential respondents. The survey is used for health communications planning by organizations (including the U.S. Centers for Disease Control and Prevention) that influence the design and administration of the questionnaire. From a stratified random sample of 5845 adults, 4035 (69%) agreed to participate in HealthStyles 2003. The survey sampling was generated on the basis of age, sex, marital status, race/ethnicity, income, geographic region, household size, and population density. One adult per household was asked to respond. Low-income and minority households were oversampled to improve their representation.(30) The Centers for Disease Control and Prevention Institutional Review Board approved this study.

Respondents provided information about their age, sex, ethnicity/race, education, income, marital status, and medical history, including both personal and family history of CHD. Personal history of CHD was considered present if a respondent reported that a doctor had diagnosed CHD, such as myocardial infarction, coronary bypass graft surgery, or angioplasty. Angina was not included in the definition. Personal history of stroke was considered present if a respondent reported that a doctor had diagnosed stroke or transient ischemic attack. For both CHD and stroke, respondents indicated whether their diagnosis came at or before age 60 years (early onset) or after age 60 years (late onset). Respondents were considered to have diabetes or obesity if they reported having either condition currently or within the past year. Hypercholesterolemia was coded as present if respondents reported ever being told by a health professional that they had high blood cholesterol or were told to take medication for high cholesterol. Hypertension was considered present if respondents reported ever being told on two or more office visits that they had high blood pressure or were ever prescribed medication to lower their blood pressure. Hypertension or diabetes diagnosed during pregnancy was excluded.

Family history assessment
Family history was obtained from respondents by asking them whether CHD had been diagnosed at or before age 60 years (early onset) or after age 60 years (late onset) in first-degree relatives (mother, father, and siblings) and second-degree relatives (aunts, uncles, and grandparents). Response options included yes, no, and don't know. Respondents also reported whether they had zero, one, or two or more siblings or second-degree relatives diagnosed with CHD.

The method of familial risk assessment under evaluation in this study used a hierarchal array of specific characteristics that took into account whether CHD was diagnosed at an early, late, or unknown age of onset in a respondent's first- and second-degree relatives, and was based on empirical data from the literature.(31,32) A weak risk was assigned if there was (1) no family history of CHD or (2) CHD in only one second-degree relative from one or both sides of the family. Moderate risk was assigned if there was (1) only one first-degree relative with late-onset CHD, (2) only one first-degree relative with late-onset CHD and one second-degree related with late-onset CHD from the same lineage, (3) only a mother and a father with late-onset CHD, (4) only one second-degree relative with early-onset CHD and one second-degree relative with late-onset CHD from the same lineage, or (5) only two second-degree relatives with late-onset CHD from the same lineage. Strong familial risk was assigned for all other family histories of CHD, including having at least one first-degree relative with early-onset CHD, and combinations of multiple affected family members. Don't know responses were considered as no responses.

Statistical analyses
We used descriptive statistics to characterize respondents, chi-square tests to assess differences in proportions, and the Student t test to assess differences in means. Odds ratios (ORs) were calculated to assess associations between self-reported early-onset CHD compared with late-onset CHD (n = 79) and no CHD, and moderate or strong familial CHD risk compared with the referent of weak familial risk using multivariate logistic regression with (1) adjustment for demographic factors only and (2) adjustment for demographics plus personal history of stroke, obesity, hypertension, hypercholesterolemia, and diabetes. Similar calculations were conducted to assess the associations between moderate or strong familial CHD risk and diabetes, hypercholesterolemia, hypertension, and obesity after (1) adjusting for demographic factors only and (2) adjusting for demographics plus personal history of CHD and stroke at any age of onset. The Breslow Day test for OR heterogeneity was performed to assess interactions between the different levels of familial risk and diabetes, hypercholesterolemia, hypertension, and obesity. No significant interactions were found (P < .05); therefore, none were included in the models. The ability to identify people with reported early-onset CHD using risk assessment models that included familial risk stratification, demographic factors, and the related conditions of diabetes, hypercholesterolemia, hypertension, and obesity (both alone and in combination) was evaluated using area under the curve (AUC) statistics, which were calculated using multivariate logistic regression. AUC greater than 75% suggested good discriminatory ability. All statistical analyses were performed using SAS v8.2 (SAS Institute, Cary, NC).

The characteristics of the 4035 respondents by category of familial risk of CHD are presented in Table 1. Of the total population sample, 60% were female and 72% were white with a mean age of 48.4 years (standard deviation 14.4). The mean ages of respondents with strong and weak familial risk of CHD were significantly older and younger, respectively, than the mean age of the total population (P < .0001). Significantly more white respondents had strong and moderate familial risk, and fewer white respondents had weak familial risk than respondents of other ethnic/racial groups. No significant differences were found between the proportion of other ethnic/racial groups among the different familial risk groups and the total population. In addition, no significant differences were found between the frequencies of educational level, income, or marital status among the respondents in different familial risk categories and the total population. However, compared with the total population frequencies, significantly more respondents in the strong familial risk group reported personal history of early-onset CHD, early-onset stroke, diabetes, obesity, hypertension, and hypercholesterolemia, and significantly more respondents in the weak familial risk group reported lower frequencies of early-onset CHD, hypertension, and hypercholesterolemia. No significant differences in the frequency of these conditions were found between the moderate familial risk group and the total sample.

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Table 1: Characteristics of respondents overall and by familial coronary heart disease risk categories (HealthStyles 2003 Survey of Health-related Attitudes and Behaviors Among the U.S. Adult Population)

The results showed that 31.5% of respondents had strong familial risk of CHD, 11.7% had moderate familial risk of CHD, and 56.8% had weak familial risk of CHD. Approximately half of the respondents reported having one or more first- or second-degree relatives with CHD. Respondents reported more don't know responses for second-degree relatives (maternal aunts, uncles, and grandparents, 31.7%; paternal aunts, uncles, and grandparents, 38.4%) compared with first-degree relatives (mother, 7.6%; father, 11.4%; siblings, 6.1%). Age, personal history of CHD, marital status, education, and income significantly influenced differences in proportions of don't know responses (P < .05). Sex and ethnicity did not. The proportion of don't know responses was significantly different for mother versus father, and maternal aunts, uncles, and grandparents versus paternal aunts, uncles, and grandparents (P < 10-6). However, these differences were not significant after adjustment for demographic variables and personal history of CHD.

Prevalence ORs for moderate and strong familial risk associated with early-onset CHD compared with weak familial risk are shown in Table 2. After adjustment for demographic factors, strong and moderate levels of familial risk were associated with a 4.9-fold (95% confidence interval [CI], 3.3-7.2) and 2.0-fold (95% CI, 1.1-3.6) increase, respectively, in risk of early-onset CHD. Modest decreases were noted in the strength of these associations after additional adjustment for personal history of stroke at any age of onset and/or personal history of the related conditions of diabetes, hypercholesterolemia, hypertension, and obesity. Even with this additional adjustment, however, the association between early-onset CHD and strong familial risk remained significant.

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Table 2: Associations between familial coronary heart disease risk categories and early-onset coronary heart disease

Strong familial risk was significantly associated with diabetes (OR = 1.5; 95% CI, 1.3-1.8), hypertension (OR = 1.5; 95% CI, 1.3-1.8), hypercholesterolemia (OR = 1.4; 95% CI, 1.6-1.9), and obesity (OR = 1.5; 95% CI, 1.3-1.8). After adjustment for demographic factors, moderate familial risk was significantly associated with hypercholesterolemia (OR = 1.5; 95% CI, 1.2-1.9) but not with the other conditions (Table 3). The strength of these associations was unchanged or only slightly reduced after adjusting for demographics plus personal history of CHD or stroke at any age of onset.

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Table 3: Associations between familial coronary heart disease risk categories and the related conditions of obesity, hypertension, hypercholesterolemia, and diabetes

Table 4 shows the association of familial risk and the number of other conditions (i.e., diabetes, hypercholesterolemia, hypertension, and obesity) with early-onset CHD. Weak familial risk plus no other condition was the referent group. Early-onset CHD increased exponentially as the number of conditions and familial risk increased. Strong familial risk plus three or more conditions was associated with a 62.2-fold increase (95% CI, 18.5-209.1) in early-onset CHD compared with the referent group. Having weak familial risk plus three or more conditions (OR = 16.5; 95% CI, 4.4-61.2) was comparable to strong familial risk plus one condition (OR = 17.9; 95% CI, 5.3-61.0).

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Table 4: Early-onset coronary heart disease associated with weak, moderate, and strong familial coronary heart disease risk and increasing number of related conditions including obesity, hypertension, hypercholesterolemia, and diabetes

In Table 5, the results of the AUC analyses are shown for seven different risk assessment models for early-onset CHD that consider alone or in combination: familial risk stratification; demographic factors; and personal history of diabetes, hypercholesterolemia, hypertension, and obesity. Familial risk stratification alone had the smallest AUC value; however, it still had relatively good discriminatory ability (AUC 70.9%). The discriminatory ability of the familial risk stratification model improved considerably with the addition of demographic factors or personal history of diabetes, hypercholesterolemia, hypertension, and obesity, with AUC values of 82.3% and 84.6%, respectively. The optimum model for identifying people with early-onset CHD included assessments of all three criteria (i.e., familial risk; demographics; and personal history of diabetes, hypercholesterolemia, hypertension, and obesity), with an AUC of 87.2%.

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Table 5: Ability of different coronary heart disease risk assessment models to identify people with early-onset coronary heart disease

We found that a method of familial risk assessment that included information about family history of early- and late-onset CHD in first- and second-degree relatives could stratify risk for early-onset CHD into three categories, with an increase of approximately fivefold in early-onset CHD given a strong familial risk and a twofold increase in early-onset CHD given a moderate familial risk compared with a weak familial risk (Table 2). We also found that diabetes, hypercholesterolemia, hypertension, and obesity were associated with a 1.4- to 1.6-fold increase given strong familial risk, and that hypercholesterolemia was associated with a 1.5-fold increase given moderate familial risk, suggesting aggregation of these conditions in the highest risk families, that is, families with early-onset CHD or multiple affected relatives (Table 3). Furthermore, as demonstrated in Table 4, the risk of early-onset CHD increased substantially when respondents had an increasing number of CHD risk factors (diabetes, hypercholesterolemia, hypertension, or obesity) in combination with moderate or strong familial risk, and the absence of these conditions diminished the association between family history and CHD. These results have important implications for CHD prevention and suggest that people with even the strongest family histories of CHD might benefit from interventions for these conditions, which were prevalent among respondents with increased familial risk. This finding is supported by the work of Tavani and colleagues,(33) who showed that people with increased familial risk for CHD may derive the greatest benefit from preventive strategies intervening on lifestyle risk factors.

The major strengths of this study were the large number of respondents to the HealthStyles 2003 survey, with equal representation of the sexes across a range of adult age groups, and the fact that the survey data correlated well with surveillance data from the Behavior Risk Factor Surveillance System.(30) However, because of the small number of respondents with late-onset CHD (n = 79), we were unable to assess the associations between familial risk and that outcome. In addition, although the survey was population based, it was subject to selection bias, because participation was voluntary; thus, the survey respondents were not randomly drawn from the U.S. population. Furthermore, the cross-sectional design prohibited us from establishing any temporal associations concerning family history as a CHD risk factor, and because the data were obtained from prevalent cases, the results may have been confounded by survival.

Another potential limitation was the lack of validation of self-reports. A previous study showed that self-reports of personal history of CHD and risk factors are reliable,(36) and several studies have investigated the validity of family history reports. For family history of CHD in first-degree relatives, sensitivity ranged from 67% to 89%, and specificity ranged from 59% to 97%, with most values greater than 90%.(6,37-41) A personal history of CHD or having a CHD risk factor such as hypertension, diabetes, or hypercholesterolemia generally does not affect the accuracy of the family history report, nor does gender.(38,39,41) However, older respondents are more likely than younger respondents to give inaccurate reports of family history.(38,41) Limited information is available regarding the influence of ethnicity/race on the accuracy of family history reports. However, in the National Heart, Lung, and Blood Institute Family Heart Study, no significant differences were found in family history accuracy between whites and African Americans reporting on CHD, diabetes, and hypertension.(38) Given these estimates of validity, a family history of CHD generally can be considered as accurate, with little overreporting of disease in close family members.

Awareness of family history of CHD was less for second-degree relatives compared with first-degree relatives. That is, there were fewer don't know responses for first-degree relatives. Because don't know responses were considered as no responses in the risk algorithms, this could lead to misclassification of some individuals as having a lower familial risk, thereby diminishing the strength of the associations we have described. Furthermore, because CHD in second-degree relatives was an important criterion in defining moderate familial risk, the lack of awareness of CHD status, particularly for second-degree relatives, may explain the lower prevalence of moderate familial risk relative to high familial risk.

We were also limited in our ability to assess all of the risk factors that might influence the association between increased familial risk of CHD and early-onset CHD, including lifestyle factors such as diet, smoking, or physical inactivity, because these data were not collected in the HealthStyles 2003 survey. Family members often share these risk factors, which could contribute to the increased familial risk that we observed in this study. However, we could not discern the contribution of these factors in our analyses, which also limited our ability to infer the possible benefit resulting from preventive interventions targeted to these risk factors.

Risk stratification using family history of CHD may improve standard global risk assessment methods for CHD. Familial risk for this disease is prevalent, and thus the evaluation of family history, in conjunction with demographics and other risk factors, should be considered as an initial step in risk assessment for CHD. Diabetes, hypercholesterolemia, hypertension, and obesity aggregate in high-risk families, and the risk of CHD associated with moderate and strong familial risk increases when these conditions are present and diminishes when they are absent. This finding suggests the potential benefit from preventive interventions on these risk factors for people with increased familial CHD risk.

This work was supported by a Career Development Award sponsored by the Association of Teachers of Preventive Medicine in collaboration with the Centers for Disease Control and Prevention, Cooperative Agreement U50/CCU300860 (M.T.S.).

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