Abstract: We identified 13 small trials (1520 participants randomised) and three ongoing trials. All studies had at least one domain with unclear risk of bias, and some studies were at high risk of bias for allocation concealment (one study) and selective reporting (two studies). Duration and style of tai chi differed between trials. Seven studies recruited 903 healthy participants, the other studies recruited people with borderline hypertension or hypertension, elderly people at high risk of falling, and people with hypertension with liver and kidney yin deficiency syndrome. No studies reported on cardiovascular mortality, all-cause mortality or non-fatal events as most studies were short term (all studies had follow-up of one year or less). There was also considerable heterogeneity between studies, which meant that it was not possible to combine studies statistically for cardiovascular risk (I2 statistic for systolic blood pressure (SBP) was 96%, for diastolic blood pressure (DBP) 96%, for total cholesterol 96%, low-density lipoprotein-cholesterol (LDL-C) 95%, high-density lipoprotein-cholesterol (HDL-C) 98%, triglycerides 75%). Nine trials measured blood pressure, six individual trials found reductions in SBP (reductions ranged from -22.0 mmHg (95% confidence interval (CI) -26.3 to -17.7) to -11.5 mmHg (95% CI -21.5 to -1.46)), two trials found no clear evidence of a difference (however, CIs were wide and an increase or decrease in SBP cannot be ruled out), and one trial found an increase in SBP with tai chi (increase 5.2 mmHg, 95% CI 3.73 to 6.67). A similar pattern was seen for DBP: three trials found a reduction in DBP (reductions ranged from -12.2 mmHg (95% CI -15.8 to -8.7) to -4.43 mmHg (95% CI -7.14 to -1.72)) and three trials found no clear evidence of a difference, however again with wide CIs. Three trials reported lipid levels and two found reductions in total cholesterol, LDL-C and triglycerides (total cholesterol reductions ranged from -1.30 mmol/L (95% CI -1.57 to -1.03) to -0.50 mmol/L (95% CI -0.74 to -0.26): LDL-C reductions ranged from -0.76 mmol/L (95% CI -0.93 to -0.59) to -0.59 mmol/L (95% CI -0.80 to -0.38): triglyceride reductions ranged from -0.46 mmol/L (95% CI -0.62 to -0.30) to -0.37 mmol/L (95% CI -0.67 to-0.07)) and increased HDL-C with the intervention (HDL-C increases ranged from 0.61 mmol/L (95% CI 0.51 to 0.71) to 0.16 mmol/L (95% CI 0.02 to 0.30)), while the third study found no clear evidence of a difference between groups on lipid levels. Quality of life was measured in one trial: tai chi improved quality of life at three months. None of the included trials reported on adverse events, costs or occurrence of type 2 diabetes. There are currently no long-term trials examining tai chi for the primary prevention of CVD. Due to the limited evidence available currently no conclusions can be drawn as to the effectiveness of tai chi on CVD risk factors. There was some suggestion of beneficial effects of tai chi on CVD risk factors but this was not consistent across all studies. There was considerable heterogeneity between the studies included in this review and studies were small and at some risk of bias. Results of the ongoing trials will add to the evidence base but additional longer-term, high-quality trials are needed.

Plain-language summary: We searched scientific databases for randomised controlled trials (clinical trials where people are allocated at random to one of two or more treatments) looking at the effects of tai chi on adults at high risk of developing CVD. We did not included people who had already had CVD (e.g. heart attacks and strokes). The evidence is current to December 2013. We found 13 trials, none of them were large enough or of long enough duration to examine the effects of tai chi on reducing cardiovascular deaths or non-fatal endpoints. There were variations in the duration and style of tai chi and the follow-up of the interventions ranged from three to 12 months. Due to the small number of short-term studies and the variability between them, we were unable to determine conclusively whether or not tai chi was beneficial at reducing cardiovascular risk in healthy adults and adults at increased risk of CVD, although beneficial effects for CVD risk factors were seen in some studies. None of the included studies reported on adverse events. Longer-term, high-quality trials are needed in order to determine the effectiveness of tai chi for CVD prevention. The results of this review should be treated with caution as the studies were small, of short duration and there was some risk of bias (where there was a risk of arriving at the wrong conclusions because of favouritism by the participants or researchers).