Tai Chi exercise improves age‐associated decline in cerebrovascular function: a cross‐sectional study

From December 2017 to March 2018, we recruited older adult Tai Chi practitioners, together with age-matched older adults and young adults as controls in Wuhan, China to evaluate the effects of Tai Chi on age-related changes in cerebrovascular functions. This study was approved by Ethical Committees from both Renmin Hospital of Wuhan University and Wuhan Sports University. This study was registered on Chinese Clinical Trial Registry (http://​www.​chictr.​org.​cn; ChiCTR1900025187), and performed in accordance with the principle of the Helsinki Declaration II. Written informed consent was obtained from all participants in advance. Inclusion criteria were based on the following: healthy older people (60–69 years old), regular practice of Tai Chi more than three year for the Tai Chi group; healthy physical active older people (60–69 years old) for older adult control group; healthy young adults (21–25 years old) for young adult control group. Exclusion criteria included: cancer, surgery history, cognitive impairment, pregnant females, gastrointestinal diseases or had gastrointestinal surgery before, abnormal liver and kidney function, evidence of acute or chronic inflammatory or infectious diseases. This is a cross-sectional study. Data were collected in a double-blinded manner.

All the participants were given a clinical and physiological examination at the Physical Examination Centre, Renmin Hospital of Wuhan University (Wuhan, China). One day before testing, all participants were advised not to consume caffeine or alcohol, smoke or engage in vigorous exercise. Blood pressure in the arms was measured using an automated oscillometric device (OMRON-M6, Omron Healthcare, Vernon Hills, Illinois, USA). We recorded the sex, age, weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate and calculated body mass index (BMI).

Left internal carotid artery hemodynamics were measured using a cerebrovascular function tester GT-3000 (Sino-medline, Beijing, China). The instrument has two probes: the Doppler probe and the pulsation pressure sensing probe. Both probes record parameters at the level of the internal carotid. Doppler probe records cerebral blood flow, cerebral blood flow rate and average blood flow. Pulse pressure sensing probe records cerebrovascular elasticity, external resistance, pulse wave velocity and other related indicators. The subjects were in a lying flat position. Cerebral vascular hemodynamics indexes (CVHI) were calculated. The recorded or calculated parameters include CVHI score, mean blood flow rate (Qmean), mean blood flow velocity (Vmean), maximum blood flow velocity (Vmax), minimum blood flow velocity (Vmin), pulse wave velocity (Wv), characteristic impedance (Zcv), dilatability (DI), resistance vascular (Rv), dynamic resistance (DR), critical pressure (CP) level, and diastolic pressure and critical pressure difference (DP).

All data were processed using SPSS 22.0 (IBM Corporation, Armonk, New York, USA) and GraphPad Prism software 8.0 (San Diego, California, USA). Sample size was predicted by the following formular n=[(Z_α/2+Z_β) × σ/ δ]²×(Q1^− 1+Q2^− 1). To carry out stratified analyses, we performed the propensity score matching process while simultaneously forcing an exact match of sex, BMI, and age between older adult control group and the Tai Chi group. Then we compared matched groups within clinical parameters. All continuous variables were summarized as mean ± standard deviation (SD), and non-normally distributed continuous variables were summarized as median (25th - 75th ). The statistical difference in continuous variables normally distributed data between the two groups was compared using the student’s t test. The Mann-Whitney U test was used for comparisons between groups for non-normally distributed continuous variables. A correlation Spearman test was used to test the coefficients of non-normally distributed continuous variables. P < 0.05 was considered statistically significant. All statistical analyses were two-tailed.

We recruited a total of 668 participants, including 289 Tai Chi practitioners aged 49–76 (117 male/172 female), together with 277 people aged 51–73 (131 male/146 female) without any Tai Chi training before and 102 young adults aged 22–25 (49 male/53 female) (Fig. 1). Among the 168 age-matched participants practicing Tai Chi for over three year, 116 (69.05%) participants regularly practice Tai Chi every day, 38 (22.62 %) participants practice Tai Chi 3–5 times per week and 14 (8.33 %) participants practice Tai Chi twice per week. The exercise frequency and other physical activities being involved were listed in Table 1.

To validate which cerebrovascular parameters indeed reflect the health status of the older adults, we first examined the correlation between each parameter and age in older adult control group calculated by Spearman’s correlation coefficient (Fig. 2). As expected, SBP was significantly correlated with age in the older adults (correlation coefficient 0.182), and was significantly higher than young controls (P = 0.002; Fig. 2 a and b). Most of the cerebrovascular function parameters, including CVHI Score, Qmean, Vmean, Vmax, Vmin, Wv, Zcv, DI, Rv and DR, were significantly correlated with age in the older adults (Fig. 2 a), indicating a strong correlation between cerebrovascular function and age. Blood flow velocity Vmean and Vmin are indicators reflecting the blood flow status of cerebrovascular blood vessels. Lower speed of cervical arterial blood flow reflects the insufficient blood supply. We found that Vmean and Vmin ranked top with high correlation efficient [− 0.303 (P < 0.001) and − 0.353 (P < 0.001), respectively], and also significantly decreased in the older adults compared with young controls (Fig. 2 a and c-e). These data suggest that cerebrovascular function serves as a reliable marker to reflect the health status of the older adults.

To evaluate the effects of Tai Chi exercise, we ran a matching program between Tai Chi group and the older adult control group aged 60–69 years old based on a propensity score to reduce the bias of age, sex and BMI. A total of 168 Tai Chi practitioners were successfully matched to 168 older adult controls, and were used for further analysis. There were no significant differences in basic physiological characteristics between the matched two groups (P > 0.05) (Table 2).

CVHI Score is an overall evaluation score for cerebrovascular hemodynamic analysis. Compared with the older adult controls, Tai Chi practitioners showed a significant increase in CVHI Score [86.63 (72.25–95.00) in Tai Chi group and 91 (81.25–98.31) in older adults control group; P = 0.002], which almost approached the level in young control group [92.25 (86.63–97)] (Table 3). In detail, Tai Chi significantly increased the carotid blood flow velocity including Vmean (P = 0.014), Vmax (P = 0.04) and Vmin (P < 0.001). Wv and Zcv are indicators of the atherosclerosis degree of the brain, and associated with the overall elasticity of the arterial wall; and Rv reflects the degree of flow of small blood vessels and capillaries. We found that Tai Chi practice significantly reduced arterial resistance indices [Wv (P = 0.022), Zcv (P = 0.021) and Rv (P = 0.044)] (Table 3). These data suggest a rejuvenation of the carotid hemodynamics by Tai Chi exercise in the older adults.