This study involved a cross-sectional design. Data were collected from 2007 to 2008 in the First Affiliated Hospital of Shantou University Medical College.

The study population was a random cluster sample from company staff or community subjects in the Jinping district of Shantou (Guangdong, China) who were undergoing an annual physical examination in the hospital healthcare center. From 4,020 possible subjects, we recruited 596 with mild to moderate essential hypertension (sitting diastolic blood pressure 90–110 mmHg and/or sitting systolic blood pressure 140–180 mmHg from 3 consecutive measurements 19). Only subjects who had regular sexual intercourse with marital partners were enrolled. People were excluded if they had ischemic heart disease, diabetes, chronic obstructive pulmonary disease, obstructive sleep apnea syndrome, cerebrovascular disease or other diseases that would interfere with sexual function or who used sex-enhancing medication. People using pacemakers and electrocardiography (ECG)-diagnosed atrial fibrillation/flutter were excluded. Finally, 502 subjects with hypertension were enrolled.

Subjects were given a detailed information sheet on the study procedure and were asked to give their signed informed consent to be in the study. The study was approved by the ethics committee of the First Affiliated Hospital of Shantou University Medical College. Interviews were conducted face to face on an individual basis by a trained researcher who used a structured questionnaire. The collection of all data took approximately 20 min. Patient data were strictly anonymous.

From the same population, we matched subjects with hypertension by age and sex with eligible subjects with normotension as controls and included 173 controls.

The investigator collected data on age, sex, occupational status, education and income for both normotensive and hypertensive subjects. Daily alcohol consumption, cigarette smoking and tea drinking were classified as never, moderate or heavy. We defined moderate smoking as fewer than 5 cigarettes/day and heavy smoking as 20 or more cigarettes/day 20. Moderate and heavy alcohol consumption were defined as total intake of alcohol, beer or wine < 20 g/day and > 20 g/day, respectively 21.

Subjects completed a self-administered questionnaire about sexual function and activity, as well as satisfaction, that was designed to fit the local culture. It was modified and validated in preliminary tests. It consisted of 9 items: “How frequently do you usually have sexual activity with your partner in a month?”, “How frequently do you experience orgasm in a month?” “How many times do you consider your sexual activity satisfactory?” “How long is your usual sexual encounter in minutes?” “Which is the usual coital position adopted: man on top, woman on top or other?”, “How do you feel during the sexual activity: comfortable, having chest pain, headache, discomfort?” Male subjects were additionally asked “How long can your erection be maintained in minutes?”

Height and weight were measured and the body mass index (BMI) was calculated as weight/height² (kg/m²). Blood pressure was measured with the patient in a seated position after a 5-min rest on 3 separate visits. Patients underwent standard 12-lead ECG with use of a Nihon Kohden ECG-9130P-type electrocardiograph.

Chi-square test was used to compare differences in categorical variables. Odds ratios and 95% confidence intervals (95% CI) were calculated to assess the likelihood of characteristics of sexual activity and life factors for hypertensive men and women. Stepwise multinomial logistic regression analyses used to evaluate potential risk factors of sexual domains. The independent variables included in the multivariate regression models were sociodemographic data and daily life habits. A p < 0.05 was considered statistically significant. The power of tests of sexual frequency between each subgroup was > 99% by NCSS-PASS (2005 version). Statistical analyses involved use of SPSS 15.0 (SPSS Inc., Chicago, IL).

Data were available for 675 subjects who reported having regular sexuality, including 502 with hypertension (225 males, mean age 48.79 ± 7.39 years [range 31-65 years]; 277 females, mean age 48.26 ± 6.93 years [range 31-63 years]) and 173 with normotension (82 males, mean age 45.69 ± 6.58 years; 91 females, mean age 46.14 ± 7.03 years (range 32-62 years) (Table 1). All women were less educated than men and were more frequently retired or unemployed than men. The sexes differed in cigarette smoking and alcohol use. Nearly half the enrolled subjects were heavy tea drinkers. Even though the blood pressure of patients with hypertension was mild to moderate, more than half did not use anti-hypertensive medicine.

Data are number (%) unless indicated.

SBP, systolic blood pressure; DBP, diastolic blood pressure; ACE1/ARB, angiotensin-converting enzym 1/angiotensin receptor blocker; CCB, calcium channel blocker.

Hypertensive and normotensive subjects differed in frequency of orgasm and sexual activity, as well as duration of sexual activity (p < 0.01; Table 2). Of the 225 males with hypertension, 57 (25.3%) reported sexual intercourse less than once per month (low frequency), 77 (34.2%) more than once per week (high frequency), with the remaining reporting intermediate activity (medium frequency). Of women with hypertension, 102 (36.8%) reported low-frequency sexual activity and 52 (20.6%) high-frequency sexual activity. Only 15 men (6.7%) experienced no orgasm during sexual activity, which coincided with the 6.7% who reported no sexual satisfaction. However, 172 women (62.1%) reported no orgasms, but only 80 (28.9%) considered their sexual life unsatisfactory. About half of the subjects, whether with hypertension or normotension, reported sexual intercourse lasting 6 to 20 min each time, and 7.5% with hypertension and 30.1% with normotension reported the intercourse lasting < 5 min. Man on top appeared to be the favored coital position, with more than 75.5% reporting this position. In total 422 subjects with hypertension (84.1%) and 165 with normotension (95.4%) reported no discomfort during the intercourse.

Data are number (%); ^**P < 0.01.

For males with hypertension, low frequency of sexual activity and orgasms and sexual satisfaction were associated with unemployed or retired employment status than physical labor (OR 0.28 [95% CI 0.12–0.69], 0.32 [0.12–0.86], 0.33 [0.19–0.88], respectively; p < 0.05). As well, longer duration of sexual activity was associated with never consuming alcohol than heavy drinking (4.49 [1.28–6.41]) (Table 3). For women with hypertension, low frequency and duration of sexual activity and sexual satisfaction were associated with never drinking tea than heavy tea drinking (0.42 [0.18–0.96], 0.49 [0.24–0.98], 0.29 [0.14–0.64], respectively; p < 0.05). Medication use and ECG results were not associated with sexual activity for hypertensive subjects.

^*P < 0.05.

The main limitation of this study was the self-reporting methodology. Self-reported sexual frequency may be higher than reported because patients may give a socially desirable answer about their sexual function. The items in the self-developed questionnaire may not be sufficient, but enrolled subjects might not be cooperative enough to complete a long questionnaire in the hospital. In addition, several other factors not measured, including side effects of anti-hypertensive medication, may influence sexual activity among people with hypertension, although two-thirds of our subjects with hypertension took no medications. Finally, the sample size of the normotensive group was relatively small as compared with the hypertensive group because most people with normotension were unwilling to participate in the study. Persuading healthy people to undergo a medical checkup and provide answers to sensitive issues, even with payment is difficult.