TABLE 3.
Subgroup meta-analysis results for stroke and all-cause mortality outcomes1
| Stroke | All-cause mortality | |||||||
|---|---|---|---|---|---|---|---|---|
| n | Pooled adjusted RR (95% CI) | P for pooled RR | I 2, % | n | Pooled adjusted RR (95% CI) | P for pooled RR | I 2, % | |
| Overall | 13 | 0.959 (0.934, 0.985) | 0.002 | 63.9** | 18 | 0.979 (0.967, 0.991) | 0.001 | 73.7** |
| Sex | ||||||||
| Both sexes | 7 | 0.956 (0.922, 0.992) | 0.016 | 74.3** | 9 | 0.967 (0.946, 0.989) | 0.003 | 75.6** |
| Female | 3 | 0.956 (0.913, 1.001) | 0.056 | 0.0 | 4 | 0.992 (0.968, 1.017) | 0.549 | 58.3* |
| Male | 3 | 0.972 (0.890, 1.062) | 0.526 | 77.1** | 5 | 0.986 (0.963, 1.009) | 0.0223 | 77.8** |
| Tea type | ||||||||
| Black tea | 5 | 0.971 (0.936, 1.008) | 0.119 | 57.8** | 10 | 0.991 (0.966, 1.016) | 0.484 | 74.7** |
| Green tea | 8 | 0.943 (0.902, 0.986) | 0.009 | 70.1** | 8 | 0.969 (0.957, 0.981) | <0.0001 | 65.3** |
| All tea | 0 | n/a | n/a | n/a | 0 | n/a | n/a | n/a |
| Age group | ||||||||
| Adults | 13 | 0.959 (0.934, 0.985) | 0.002 | 63.9** | 15 | 0.985 (0.975, 0.996) | 0.006 | 60.4** |
| Elderly | 0 | n/a | n/a | n/a | 3 | 0.920 (0.898, 0.942) | <0.0001 | 0.3 |
| Region | ||||||||
| United States | 2 | 0.969 (0.926, 1.013) | 0.0165 | 0.0 | 5 | 0.979 (0.951, 1.007) | 0.140 | 69.4** |
| Asia | 5 | 0.943 (0.902, 0.986) | 0.009 | 70.1** | 8 | 0.969 (0.957, 0.981) | <0.0001 | 65.3** |
| Europe | 6 | 0.971 (0.922, 1.023) | 0.266 | 68.8** | 4 | 1.024 (0.975, 1.075) | 0.349 | 80.0** |
| Australia | 0 | n/a | n/a | n/a | 1 | 0.900 (0.814, 0.995) | 0.040 | n/a |
| Iran | 0 | n/a | n/a | n/a | 0 | n/a | n/a | n/a |
| Risk of bias | ||||||||
| Exposure ascertainment2 | ||||||||
| A | 5 | 0.978 (0.918, 1.041) | 0.480 | 66.6** | 4 | 1.005 (0.972, 1.040) | 0.751 | 85.8** |
| B | 6 | 0.954 (0.929, 0.980) | 0.001 | 52.0* | 5 | 0.988 (0.968, 1.009) | 0.023 | 64.8** |
| C | 2 | 0.917 (0.794, 1.058) | 0.236 | 84.7** | 9 | 0.957 (0.937, 0.979) | <0.0001 | 71.3** |
| No outcomes at start3 | ||||||||
| A | 13 | 0.959(0.934, 0.985) | 0.002 | 63.9** | 14 | 0.985 (0.974, 0.997) | 0.012 | 68.7** |
| B | 0 | n/a | n/a | n/a | 4 | 0.927 (0.907, 0.948) | <0.0001 | 0.0 |
| Comparability4 | ||||||||
| AB | 11 | 0.972 (0.948, 0.997) | 0.026 | 63.9** | 14 | 0.985 (0.974, 0.997) | 0.012 | 68.7** |
| A | 0 | n/a | n/a | n/a | 1 | 0.900 (0.814, 0.995) | 0.040 | n/a |
| B | 2 | 0.887 (0.834, 0.943) | <0.0001 | 30.2 | 3 | 0.929 (0.908, 0.950) | <0.0001 | 0.0 |
| Adequate follow-up5 | ||||||||
| A | 6 | 0.959 (0.903, 1.008) | 0.094 | 66.4** | 6 | 0.981 (0.936, 1.028) | 0.423 | 80.7** |
| B | 7 | 0.962 (0.931, 0.994) | 0.019 | 66.9** | 11 | 0.982 (0.972, 0.991) | <0.0001 | 48.3** |
| C | 0 | n/a | n/a | n/a | 1 | 0.925 (0.902, 0.949) | <0.0001 | n/a |
| D | 0 | n/a | n/a | n/a | 0 | n/a | n/a | n/a |
n = number of studies. *,**Indicates significant heterogeneity based on Q-test: *P < 0.1, **P < 0.05. CVD, cardiovascular disease; n/a, not applicable.
Ascertainment of exposure: A, multiple dietary exposure assessments during follow-ups and having internal or external calibration of the dietary assessment instrument, or single dietary exposure assessment at baseline and having internal or external calibration of dietary assessment for tea or flavonoid consumption specifically; B, single dietary exposure assessment at baseline and having internal or external calibration of the dietary assessment instrument; and C, single dietary exposure assessment at baseline and unclear validity of the dietary assessment instrument.
Demonstration that the outcome of interest was not present at the start of the study: A, yes; B, no.
Comparability of cohorts on the basis of the design or analysis: A, study controls for age, sex, socioeconomic characteristics (e.g., education, income), any anthropometric measure (BMI, weight, etc.), medication for or history/existing diseases if applicable [choose this when 1) must include all of them or 2) if they describe having a variable selection process, and justify why they did not include some of these]; B, study controls for any additional factor such as other dietary factors or physical activity; C, both A and B; and D, neither A nor B. Note that AB indicates both A and B.
Adequacy of follow-up of cohorts: A, complete follow-up, all subjects accounted for (e.g., mortality as results and use death record linkage data); B, subjects lost to follow-up unlikely to introduce bias—small number lost (≤20%), or >20% lost to follow-up, with description provided of those lost; C, lost to follow-up rate ≥20% without description of those lost or likely to bring bias; and D, no statement.