Although erectile dysfunction (ED) is considered a well-established risk factor for cardiovascular disease (CVD), few studies have investigated whether other aspects of sexual function might predict CVD independently of ED. In a longitudinal, population-based study of community-dwelling men participating in the Massachusetts Male Aging Study, we examined sexual function variables (including ED) and the subsequent development of CVD. ED was defined according to a validated, discriminant-analytic formula determined from the questionnaire responses and categorized as moderate/complete ED versus none/minimal. CVD included a wide range of major end points and was ascertained through self-report, medical records, and the National Death Index. We calculated the age-adjusted incidence rates according to the person-years of follow-up, and Cox proportional hazards models were used to estimate covariate-adjusted, Framingham risk score-adjusted, and ED-adjusted hazard ratios and 95% confidence intervals for sexual function variables and the subsequent risk of CVD. Of the 1,165 men free of CVD at baseline, the age-adjusted CVD incidence rate for moderate/complete ED and none/minimal ED was 17.9/1,000 person-years and 12.5/1,000 person-years, respectively. In multivariate models adjusted for age, covariates, ED, and the Framingham risk score, a low frequency of sexual activity (once a month or less vs ≥2 times weekly) was associated with increased risk of CVD (hazard ratio 1.45, 95% confidence interval 1.04 to 2.01). In conclusion, our results suggest that a low frequency of sexual activity predicts CVD independently of ED and that screening for sexual activity might be clinically useful.
Longitudinal studies have shown that erectile dysfunction (ED) is a risk factor for incident cardiovascular disease (CVD) and CVD mortality. However, little is known about how or whether other aspects of sexual health, in addition to ED, are associated with the development of CVD. The objective of the present analysis was to examine, in a population-based study of community-dwelling men, whether non-ED aspects of sexual function (including the frequency of sexual activity and satisfaction with sex life) are associated with the subsequent development of CVD, independently of ED status. If associated with an increased risk, these additional aspects of sexual health beyond ED might prove useful as additional risk markers or clinical screening criteria. Although past studies have considered sexual activity and intercourse frequency and subsequent CVD or stroke, to our knowledge, this is the first study that has considered a broad range of sexual function parameters and CVD risk.
Methods
The Massachusetts Male Aging Study (MMAS) is a population-based, longitudinal cohort study of aging, health, and endocrine and sexual function conducted among a random sample of men observed at 3 points (T1, 1987 to 1989; T2, 1995 to 1997; and T3, 2002 to 2004). The sampling design and field protocol have been previously described. In brief, men aged 40 to 70 years old were randomly selected from 11 cities and towns near Boston, Massachusetts. Men in older age groups were oversampled to provide approximately equal proportions in each age decade (age 40 to 49, 50 to 59, and 60 to 70 years). At baseline (T1, 1987 to 1989), 1,709 men (52% of 3,258 eligible) were enrolled in the study. These response rates were expected, given the requirements for early-morning phlebotomy and extensive in-person interviews. A telephone survey of nonrespondents (n = 206) revealed that they were similar to the respondents in general health and the prevalence of chronic diseases. The MMAS subjects were observed again in 1995 to 1997 (T2, n = 1,156, 77% response rate) and 2002 to 2004 (T3, n = 853, 65% response rate). The MMAS participants were typically white (95%), employed (78%), and married (75%), and most had completed a high school education (71%). The low representation of racial minorities (5%) was similar to the racial composition of the general population of Massachusetts. Data from the 1990 US Census indicate that only 9% of men aged 40 to 69 years in Massachusetts were nonwhite. MMAS received institutional review board approval, and all participants gave written informed consent.
A trained field technician/phlebotomist visited each subject in his home. Anthropometric data on height, weight, and waist and hip circumference were obtained using standardized procedures developed for large-scale epidemiologic field studies. Two blood pressure measures were obtained during the interview at two time points, 25 minutes apart, and averaged. The following information was collected by interviewer-administered questionnaire: demographics, psychosocial factors, history of chronic disease, self-assessed general health status, tobacco and alcohol use, nutritional intake, a full medication inventory, a set of common complaints (e.g., headaches, backaches, trouble sleeping), and physical activity/energy expenditure during the past 7 days. Also, we constructed the Framingham risk score, which gives the 10-year estimated probability of a coronary heart disease event according to Adult Treatment Panel III Guidelines, using age, total cholesterol, high-density lipoprotein cholesterol, blood pressure, diabetes, and smoking status.
During the in-home visit at T1, a self-administered questionnaire was used to evaluate sexual function. The questionnaire included 23 items related to sexual function and had been adapted from previously validated instruments. It had been field-tested and was self-administered in private at the end of an hour-long interview. A validated algorithm was used to identify men with ED. In brief, the responses to questions pertaining to self-reported aspects of sexual function, including frequency of activity, quantity of erections, awakening with erections, frequency of ejaculation, attitudes about sexual decline, and sexual arousal levels compared to adolescence were used to classify men in the MMAS as having none, minimal, moderate, or complete ED. In the present analysis we classified men with ED as having moderate or complete ED. Sexual function variables, in addition to ED, that were considered independently in the present analysis are listed in Table 1 .
| Question |
|---|
| How satisfied are you with your sex life? |
| How satisfied are you with your sexual relationship with your present partner or partners? |
| How satisfied do you think your partner(s) is (are) with your sexual relationship? |
| Has the frequency of your sexual activity with a partner been (as much as you desire/less than you desire/more than you desire)? |
| How frequently do you feel sexual desire? |
| In an average week, how frequently do you usually have sexual intercourse or activity? |
| Compared with when you were an adolescent (around 18–20 years) do you feel sexually aroused? (more than, about the same, less than) |
The data on CVD were obtained from 3 sources: self-report, linkage of the MMAS database with the National Death Index (NDI), and medical records. Self-reports included a wide range of major CVD end points (i.e., myocardial infarction, stroke, coronary artery bypass graft surgery, congestive heart failure). Those who gave positive endorsement of any of these were considered to have CVD. According to the medical records and NDI (underlying cause), CVD was determined according to the International Classification of Diseases (ICD). Before 1999, the events/deaths were coded according to the ICD, Ninth Revision, and, subsequently, according to the ICD, Tenth Revision. Subjects with ICD-9/ICD-10 codes 390-459/I00-I99, which include coronary heart disease, heart failure, peripheral vascular disease, cerebrovascular disease, and other vascular diseases, were considered cases of CVD. Of the 298 cases of CVD, 83 were obtained by self-report only, 37 were identified by NDI only, and the remaining 178 from the medical records. We also performed analyses restricting CVD cases to those whose CVD status was confirmed by medical record or NDI (n = 215). In that analysis, self-reported CVD cases were considered noncases, and their person-years were appropriately adjusted.
Men who reported CVD at baseline were excluded from the analyses (n = 266). The remaining men were required to have complete ED data at baseline (n = 1,165). Person-years were accumulated from each subject’s baseline visit to the date of the last observation or event date. We computed the incidence rates (cases/person-years) with the 95% confidence intervals (CIs) under the assumption that such rates followed a Poisson distribution. The rates were internally age-adjusted to the age distribution of the analysis sample. A hazard ratio (HR) was calculated using the Cox proportional hazards regression model. The covariate adjustment included marital status, employment status, education, waist circumference, and self-rated overall health. For subjects with no CVD who were observed at follow-up, the status of each covariate was updated at that time. Each subject could therefore contribute ≤2 nonoverlapping risk intervals to the analysis. The tests for linear trend across exposure categories were performed by creating linear contrasts. Significance was considered present when p <0.05. All analyses were conducted using Statistical Analysis Systems, version 9.2 (SAS Institute, Cary, North Carolina).
Results
Overall, 1,165 men were included in the present analysis, of whom 213 had ED at baseline. The men were followed up for an average of 16.2 years. Table 2 lists the baseline characteristics of the men according to ED status. The men with ED were older on average (59 ± 8 years) than the men without ED (53 ± 8 years). The men with ED had a lower household income, were more likely to have been diagnosed with hypertension or diabetes, had worse overall self-reported health, a greater prevalence of smoking, and a slightly greater body mass index. Overall, 40% of men with ED were in the greatest risk category for the Framingham risk score compared to 19% of men without ED. ED was significantly related to the age-adjusted CVD incidence rates (p = 0.04; Table 3 ). For the binary ED variable, the CVD incidence was 12.5 (95% CI 10.8 to 14.3) per 1,000 person-years among men with none/minimal ED and was 17.9 (95% CI 14.1 to 22.6) per 1,000 person-years among men with moderate/complete ED (p = 0.03).
| Variable | Subjects Without ED (n = 952) | Subjects With ED (n = 213) |
|---|---|---|
| Age (years) | 53.8 ± 8 | 59.8 ± 8 |
| Marital status | ||
| Never married | 87 (9%) | 21 (10%) |
| Currently married | 736 (77%) | 158 (74%) |
| Divorced/separated | 107 (11%) | 26 (12%) |
| Widowed | 22 (2%) | 8 (4%) |
| Education | ||
| High school or less | 212 (22%) | 83 (39%) |
| Some college or bachelor’s degree | 398 (42%) | 85 (40%) |
| Advanced study bachelor’s degree | 342 (36%) | 45 (21%) |
| Annual household income | ||
| <$40,000 | 295 (32%) | 102 (50%) |
| $40,000–$79,999 | 414 (44%) | 74 (36%) |
| ≥$80,000 | 225 (24%) | 29 (14%) |
| Hypertension | 244 (26%) | 71 (33%) |
| Diabetes mellitus | 50 (5%) | 22 (10%) |
| Self-assessed health | ||
| Excellent | 354 (37%) | 45 (21%) |
| Very good | 363 (38%) | 77 (36%) |
| Good | 192 (20%) | 75 (35%) |
| Fair/poor | 41 (4%) | 16 (8%) |
| Current smoker | 217 (23%) | 56 (26%) |
| Body mass index (kg/m 2 ) | 27.0 ± 4.24 | 27.5 ± 4.47 |
| Waist circumference (in.) | 38.0 ± 4.37 | 38.9 ± 4.81 |
| Framingham risk score category (%) | ||
| <5 | 163 (17%) | 14 (7%) |
| 5–10 | 293 (31%) | 51 (24%) |
| 10–20 | 316 (33%) | 63 (30%) |
| >20 | 180 (19%) | 85 (40%) |
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