Methods

This study used a randomized study design to investigate the effectiveness of mind–body meditation approach on improvements BP, BMI, lipid profiles, and quality of life factors associated with hypertension and age-related chronic disease. The study population consisted of a sample of Chinese adults aged 45 to 80 years in Changshu, Jiangsu Province, and Fang Shan District, Beijing, China. Both Changshu and Fangshan were selected as the study sites because of their well-developed economic status in China, which has resulted in dramatic changes in the lifestyle, dietary, and disease patterns of the residents in recent years. The trial was registered in International Standard Randomized Controlled Trial with Number ISRCTN 87289137 (Web address: http://www.controlled-trials.com/ISRCTN87289137 ). Ethical approval was obtained from the Jiangsu Province Changshu Center for Disease Control and Prevention (CDC) and Fang Shan CDC Research Review Committee in China and the Griffith University Research Ethics Committee in Australia.

To be included in the study, participants had to be aged ≥45 years and diagnosed with hypertension. This age group was chosen because they have an increased prevalence of hypertension, providing a unique opportunity to observe risk factors associated with this condition. Participants also had to be resident in Changshu city of Jiangsu Province or in the Fangshan District of Beijing, within 20 km of the metropolitan area. Participants who met these criteria were randomly selected from medical records located in the Changshu CDC and Fang Shan CDC. They then participated in a clinical interview conducted by trained physicians at the CDC or the Bureaus of Health in Changshu City and Fangshan District in Beijing. At the same time, a medical examination was conducted and a medical history taken regarding experience of chronic diseases. Participants were also asked to provide a biomedical blood sample and complete a survey measuring health-related quality of life (HRQoL) and demographic factors. People were excluded from the study if they had a neurologic impairment or could not provide consent to participate.

Of the 350 people who met the inclusion criteria, 300 participated in the clinical interview, blood sample test, and survey, representing a high response rate of 86%. All participants presented with hypertension at the time of data collection or were on hypertensive medication. Equal numbers of participants were randomly assigned to the Tai Chi intervention group (n = 150) and control group (n = 150) by the 3 physicians using a simple randomization method ( Figure 1 ). Researchers who conducted the statistical analysis and who conducted the laboratory tests were not aware of the allocation status of the participants. The sample met the statistical power requirement for a moderate effect size on systolic blood pressure (SBP) of 0.47.

Consort chart of recruitment of participants.

Participants in the intervention group attended Tai Chi training for 12 months from April 2012 to April 2014, whereas control group participants were active controls who attended non–exercise-related activities such as reading and learning computer software applications for the same period. In the Tai Chi group, participants were taught a variety of meditation techniques by an experienced trainer including breathing, balance, flexibility, concentration, calming, and stress-reduction techniques. Both Tai Chi and control group participants participated in group activities 3 h/wk and 2-hour practice by themselves at home.

After the completion of interview, data were collected using a combination of biomedical assessments and standardized questionnaires as part of a free physical examination. Participants were required to fast overnight. Fasting venous blood samples were then collected and analyzed for biomedical indicators, including total cholesterol, LDL, HDL, TG, fasting glucose, and serum creatinine (Scr). Participants, wearing light indoor clothing without shoes, were then weighed to the nearest 0.1 kg and measured to the nearest 0.1 cm in height. BMI was calculated as weight (kg)/height (m ² ). The China CDC and Ministry of Health adopted the World Diabetes Federation criteria, which is based on the BMI, and defines overweight as 25.0 to 29.9 kg/m ² and obesity as ≥30.0 kg/m ² . Waist (centimeters) girth was measured at the minimum circumference between the iliac crest and the rib cage using an anthropometric tape over light clothing. Abdominal obesity was defined as waist circumference ≥90 cm for men and ≥80 cm for women, on the basis of the World Federation Diabetes standard. SBP and diastolic blood pressure (DBP) were measured using an inflatable cuff wrapped around the upper arm (not the forearm or wrist) and attached to an electronic monitor that gave a digital readout of the BP (mm Hg) and pulse. The criteria for hypertension are SBP >140 mm Hg and DBP >90 mm Hg, on the basis of the International Diabetes Federation (IDF) and China CDC criteria.

Metabolic syndrome was based on the updated IDF criteria. Metabolic syndrome was diagnosed by the presence of central obesity assessed as mentioned previously (using cut-off values from Chinese people), plus on at least 2 other components including high TG (>1.69 mmol/L), low HDL (HDL <1.03 mmol/L for men and <1.29 mmol/L for women), elevated BP (SBP ≥130 mm Hg or DBP ≥85 mm Hg), and hyperglycemia (fasting glucose ≥5.6 mmol/L). Dyslipidemia was defined as total cholesterol ≥5.17 mmol/L, LDL ≥4.1 mmol/L, HDL-C <1.03 for men and <1.29 for women, and/or TG >1.69 mmol/L, according to the IDF definition. eGFR was used to measure renal functions using the following equation of the Modification of Diet in Renal Disease Study for Chinese eGFR (mL/min/1.73 m ² ) = 186 × [Scr] ^−1.154 × [age] ^−0.20 × [0.74 (if female)] × [1.23 (Chinese co-efficient)].

HRQoL were measured using the Short-Form 12 Health Survey, which has 12 items and is a reliable and valid means of measuring quality of life in people with chronic conditions. Two aggregate physical and mental component summary scores were also calculated on the basis of Chinese population norms. The physical health components of the Short-Form 12 Health Survey encompass (1) physical functioning; (2) role limitations due to physical health problems; (3) bodily pain; and (4) general health perception. The mental health component includes (1) vitality/fatigue; (2) social functioning; (3) role limitation due to emotional problems; and (4) mental health status.

The chief investigators were blind to the allocation of the participants. The percentage of normal and abnormal biomedical levels in a number of biomedical factors in both Tai Chi intervention group and control group at the baseline phase was compared using the chi-square test. All continuous variables were checked for normal distribution before multivariate general linear model (GLM) was used to compare differences before and after intervention in both the Tai Chi group and control group on biomedical factors and HRQoL measurements as continuous variables. Any differences between the Tai Chi and control group on demographic factors including age, gender, education, income, and marital status were controlled in the GLM when the intervention effect was analyzed. The statistical significance level was at a p value <0.05 for the chi-square and GLM tests. All statistics were conducted on the remaining participants after intervention. To examine sample biases, participants in both the intervention and control groups were compared before and after intervention on age, gender, education, income, employment, and marital status.