The clinical expression of hypertrophic cardiomyopathy (HC) is undoubtedly influenced by modifying genetic and environmental factors. Lifestyle practices such as tobacco and alcohol use, poor nutritional intake, and physical inactivity are strongly associated with adverse cardiovascular outcomes and increased mortality in the general population. Before addressing the direct effect of such modifiable factors on the natural history of HC, it is critical to define their prevalence in this population. A voluntary survey, drawing questions in part from the 2007 to 2008 National Health and Nutrition Examination Survey (NHANES), was posted on the HC Association website and administered to patients with HC at the University of Michigan. Propensity score matching to NHANES participants was used. Dichotomous and continuous health behaviors were analyzed using logistic and linear regression, respectively, and adjusted for body mass index and propensity score quintile. Compared to the matched NHANES participants, the patients with HC reported significantly less alcohol and tobacco use but also less time engaged in physical activity at work and for leisure. Time spent participating in vigorous or moderate activity was a strong predictor of self-reported exercise capacity. The body mass index was greater in the HC cohort than in the NHANES cohort. Exercise restrictions negatively affected emotional well-being in most surveyed subjects. In conclusion, patients with HC are less active than the general United States population. The well-established relation of inactivity, obesity, and cardiovascular mortality might be exaggerated in patients with HC. More data are needed on exercise in those with HC to strike a balance between acute risks and the long-term health benefits of exercise.
Lifestyle factors, such as tobacco, alcohol abuse, unhealthy food choices, and sedentary lifestyle, increase cardiovascular mortality in the general population and might modify the disease course in patients with hypertrophic cardiomyopathy (HC). A prospective study of the effect of lifestyle on the outcomes in HC would be challenging owing to the low event rates. Focusing on modification of the most problematic lifestyle behaviors for patients with HC is therefore imperative. Exercise presents a dilemma for those with HC because of concerns for triggering sudden cardiac death (SCD). In the general population, SCD risk increases acutely during a bout of exercise and is likely amplified in those with HC. Nevertheless, the absolute frequency has been predicted to be very low, ∼0.1% annually for competitive athletes, and considerably lower for recreational exercisers according to recent estimates. Uncertainty has led to the development of consensus guidelines for competitive and recreational exercise by patients with HC that discourage high-intensity exercise in favor of recreational low- to moderate-intensity exercise. Nevertheless, in the absence of objective data, healthcare providers might adopt an overly conservative approach when advising patients with HC on exercise. Also, patients themselves might be apprehensive about engaging in physical activity. Accordingly, we hypothesized that those with HC would be less physically active than the general population and that exercise restrictions would adversely affect the patients’ physical and mental health. We conducted a survey of health behaviors in a large national sample of patients with HC. The survey used questions pertaining to nutrition practices, tobacco, alcohol use, and exercise from the 2007 to 2008 National Health and Nutrition Examination Survey (NHANES) to allow comparisons to the general population.
Methods
A voluntary survey of health behaviors, derived in part from the 2007 to 2008 NHANES, was posted on the HCM Association (HCMA) website ( www.4hcm.org ) and administered to patients with HC at the University of Michigan. The survey was completed by 110 patients with HC at the University of Michigan (UM HC) and 930 HC patients from the HCMA, and the results were compared to those from 6,228 NHANES survey respondents. Because the UM HC sample contained >96% non-Hispanic white patients, the analyses were largely limited to this race/ethnic group. This left 106 UM HC, 791 HCMA, and 2,858 NHANES subjects for analysis. The University of Michigan institutional review board approved the present study, and the subjects provided written informed consent.
The subjects were matched by age and gender. Propensity score matching was used rather than individual-level matching to maximize the sample size. Logistic regression analysis was used to estimate the expected probability of each subject being a member of the NHANES sample, according to age and gender. The distribution of subjects in the 5 quintiles of predicted probabilities were compared ( Supplemental Figure 1 ) and found to overlap between the samples. Therefore, no subjects were removed from the analysis, and membership to a specific quintile was adjusted in all analyses.
Sensitivity analyses were run using a 1-to-1 “greedy” matching algorithm and a 1-to-many matching algorithm, in which 2 to 4 NHANES controls were matched to 1 patient with HC. Both of the more restrictive matching algorithms produced results very similar to those from the simple propensity score adjustment.
The hours per week of physical activity were determined by multiplying the days per week and hours per day a subject participated in the activity. Because of the presence of a few outliers in each physical activity measure, a maximum of 80 hours/week was assigned. The activity levels were classified as either vigorous (large increases in breathing or heart rate) or moderate (small increases in breathing or heart rate) conducted for ≥10 continuous minutes.
The demographics were compared between the HCMA and NHANES samples using simple t tests and chi-square tests. Dichotomous and continuous health behaviors were analyzed using logistic and linear regression, respectively, and adjusted for body mass index and propensity score quintile. Because of the high frequency of zero responses for physical activity questions, zero-inflated negative binomial models were used. SAS, version 9.2, software (SAS Institute, Cary, North Carolina) was used for all analyses.
Results
The population demographics of the HCMA, UM HC, and NHANES samples are presented in Table 1 . The racial differences between both HC cohorts and the NHANES sample were striking, with the HC population predominately non-Hispanic white (96% UM HC, 85% HCMA). The reasons for this are unclear, but speculative explanations include the local demographics of the HC centers at which patients receive education about their disease and information about national support services. More limited access to healthcare, or a reduced level of recognition by healthcare providers in minority populations, could also have contributed to the racial imbalance. In contrast, the NHANES sample was selected to represent the United States population of all ages, and those aged ≥60 years, blacks, and Hispanics were purposely oversampled.
| Characteristic | All Races | Non-Hispanic White | ||||
|---|---|---|---|---|---|---|
| UM HC (n = 110) | HCMA (n = 930) | NHANES (n = 6,228) | UM HC (n = 106) | HCMA (n = 791) | NHANES (n = 2,858) | |
| Age (yrs) | ||||||
| Mean ± SD | 50 ± 14 | 49 ± 13 | 49 ± 19 | 50 ± 14 | 49 ± 12 ∗ | 53 ± 19 |
| Range | 19–81 | 18–84 | 18–80 | 19–81 | 18–84 | 18–80 |
| Men | 62% ∗ † | 52% | 50% | 61% ∗ | 52% | 51% |
| Height (cm) | ||||||
| Mean ± SD | 174 ± 11 ∗ † | 172 ± 11 ∗ | 167 ± 10 | 174 ± 11 | 172 ± 11 ∗ | 169 ± 10 |
| Range | 137–196 | 125–203 | 137–204 | 137–196 | 125–201 | 140–199 |
| Weight (kg) | ||||||
| Mean ± SD | 96 ± 22 ∗ † | 87 ± 21 ∗ | 81 ± 21 | 95 ± 22 ∗ † | 88 ± 20 | 82 ± 21 |
| Range | 51–162 | 45–181 | 32–218 | 51–162 | 45–181 | 36–218 |
| Body mass index (kg/cm 2 ) | ||||||
| Mean ± SD | 32 ± 7 ∗ † | 30 ± 6 | 29 ± 7 | 32 ± 7 ∗ † | 30 ± 6 ∗ | 28 ± 6 |
| Range | 18–58 | 15–58 | 14–73 | 18–58 | 15–58 | 15–73 |
| >30 | 55% ∗ † | 40% ∗ | 36% | 54% ∗ † | 42% ∗ | 33% |
| Non-Hispanic white | 96% | 85% | 46% | 100% | 100% | 100% |
Before propensity matching, the HCMA cohort was significantly younger than the UM HC or NHANES group, and a greater proportion of survey respondents in the UM HC group were men compared to the other 2 groups. The mean body weight and body mass index were significantly greater in both the UM HC and the HCMA populations compared to the NHANES population. A greater percentage of respondents from the HCMA cohort reported the presence of left ventricular outflow tract obstruction or previous septal reduction therapy ( Table 2 ). Of those with implantable cardioverter defibrillators, fewer UM HC respondents reported a previous shock from their device. The reported frequency of a family history of SCD was similarly high between the groups. In the UM HC sample only ∼1/3 of reported SCDs occurred in family members <45 years old according to chart review. The ages of the family members with SCD were not available for the HCMA cohort, because this was not queried in the survey.
| Variable | UM HC (n = 106) | HCMA (n = 791) |
|---|---|---|
| Left ventricular outflow tract obstruction | 43% ∗ | 58% |
| Ventricular septal myectomy | 22% ∗ | 28% |
| Alcohol septal ablation | 3.0% ∗ | 8.0% |
| Either myectomy or alcohol septal ablation | 24% ∗ | 35% |
| Implantable cardioverter defibrillator | 33% | 43% |
| Received ≥1 shock | 18% ∗ | 36% |
| Family history of sudden cardiac death | 45% | 43% |
| Deaths reported to have occurred during physical activity | 29% | 23% |
For these and all subsequent analyses, the responses from the HCMA and UM HC samples were pooled. Overall, no definitive differences were found in the eating behaviors assessed by the standardized questions from the NHANES survey. Although the patients with HC reported eating fewer meals from fast food or frozen pizza, they also reported a threefold greater frequency of eating ready-to-eat meals in the previous 30 days ( Supplementary Table 1 ). The number of meals not prepared at home and the number of frozen meals or frozen pizza consumed in the previous 30 days was not statistically significant between the groups.
More patients with HC drank ≥12 alcoholic beverages during their lifetime and also reported having ≥12 alcoholic drinks during the past year than in the matched NHANES sample ( Supplementary Table 2 ). However, the amount of alcohol consumed during the previous year was lower in the HC cohort. Additionally, fewer patients with HC reported binge drinking (≥5 drinks in 1 day). Overall, the responses indicated a lower degree of alcohol consumption in the HC respondents than in the matched NHANES sample.
Significantly fewer HC respondents were past or current smokers compared to the NHANES population ( Supplementary Table 2 ). Of the previous smokers, the patients with HC reported smoking fewer cigarettes than did the NHANES participants at the time they had quit.
Significantly fewer subjects with HC had employment that involved vigorous activity, such as carrying or lifting heavy loads, digging, or construction, compared to the NHANES population ( Table 3 ). Of those who had employment involving vigorous activity, those with HC spent significantly less time at that level of effort (mean 7.1 vs 11.9 hours/week; Figure 1 ). Similarly, fewer patients with HC reported employment that involved moderate intensity work, characterized as brisk walking or carrying light loads for 10 minutes continuously ( Table 3 ). In this subgroup, the time spent performing moderate intensity activity at work was also significantly less for patients with HC compared to the NHANES population (mean 7 vs 10.7 hours/week, Figure 1 ).
| Behavior | HC (n = 897) | NHANES (n = 2,858) | OR ∗ (95% CI) | p Value |
|---|---|---|---|---|
| Vigorous work | 9% | 21% | 0.31 (0.24–0.41) | <0.0001 |
| Moderate work | 29% | 44% | 0.48 (0.40–0.57) | <0.0001 |
| Vigorous recreational activities | 23% | 20% | 1.24 (1.01–1.51) | 0.04 |
| Moderate recreational activities | 63% | 42% | 2.24 (1.90–2.64) | <0.0001 |
More patients with HC reported current participation in vigorous or moderate-intensity exercise for the purpose of recreation or fitness compared to the NHANES respondents ( Table 3 ). However, the time spent doing these activities was significantly less for patients with HC compared to NHANES participants (mean vigorous-intensity activity 2.2 vs 3.8 hours/week, moderate-intensity activity 2.1 vs 3.2 hours/week, respectively, Figure 1 ). Having an implantable cardioverter defibrillator or a reported family history of SCD correlated inversely with participation in recreational vigorous-intensity exercise but not moderate-intensity exercise ( Table 4 ). Self-reported dyspnea of any magnitude correlated inversely with moderate-intensity activity, but not significantly so with vigorous-intensity exercise after adjustment for demographic variables.
| Measure | % | Vigorous Activity | Moderate Activity | ||
|---|---|---|---|---|---|
| OR ∗ | p Value | OR ∗ | p Value | ||
| Family history of sudden cardiac death | 45 | 0.33 | 0.002 | 0.76 | 0.09 |
| Presence of implantable cardioverter defibrillator | 40 | 0.56 | 0.05 | 1.02 | 0.90 |
| Anxiety about exercising | 69 | 0.68 | 0.34 | 1.13 | 0.44 |
| Symptomatic status (dyspnea) | |||||
| No dyspnea | 60 | 1.00 | — | 1.00 | — |
| Any level of dyspnea | 40 | 0.78 | 0.32 | 0.65 | 0.008 |
∗ ORs were calculated after adjustment for gender, age, sample (HCMA vs UM HC), and body mass index.
Self-reported exercise capacity was assessed in patients with HC using a standardized nomogram, the Veteran’s Specific Activity Questionnaire ( Supplementary Table 3 ). The predicted maximum metabolic equivalent level using the Veteran’s Specific Activity Questionnaire is highly predictive of the actual maximum metabolic equivalent level achieved on a maximum treadmill stress test in the general population. The Veteran’s Specific Activity Questionnaire scores ( Supplementary Figure 2 ) were highly correlated with the time spent weekly performing vigorous or moderate-intensity recreational activity but not with time spent in work-related activities ( Table 5 ).
