Table 2. Stratified analysis of the association between TSH and dementia.
| Subgroup | N | Risk estimate |
Heterogeneity |
||
|---|---|---|---|---|---|
| Pooled RR (95% CI) | P1 | I2 | P2 | ||
| TSH: low category vs. middle category | 10 | 1.6 (1.27, 2.00) | <0.001 | 0.00 | 0.58 |
| Study type | |||||
| Cohort | 7 | 1.5 (1.17, 1.92) | 0.001 | 0.00 | 0.49 |
| Case-control | 3 | 2.25 (1.28, 3.96) | 0.005 | 0.00 | 0.78 |
| Data type | |||||
| TSH below vs. within the normal range | 6 | 1.77 (1.31, 2.39) | <0.001 | 0.00 | 0.76 |
| Lower vs. middle tertile of TSH within the normal range | 4 | 1.39 (0.98, 1.97) | 0.062 | 0.23 | 0.27 |
| TSH: high category vs. middle category | 9 | 0.99 (0.76, 1.29) | 0.923 | 0.17 | 0.29 |
| Study type | |||||
| Cohort | 6 | 1.14 (0.85, 1.54) | 0.385 | 0.00 | 0.65 |
| Case-control | 3 | 0.54 (0.30, 1.00) | 0.048 | 0.00 | 0.44 |
| Data type | |||||
| TSH above vs. within the normal range | 6 | 0.91 (0.61, 1.34) | 0.619 | 0.00 | 0.77 |
| Upper vs. middle tertile of TSH within the normal range | 3 | 1.07 (0.74, 1.54) | 0.734 | 0.70 | 0.03 |
| Gender: male | |||||
| Low category vs. middle category of TSH | 3 | 1.28 (0.70, 2.32) | 0.419 | 0.00 | 0.62 |
| High category vs. middle category of TSH | 3 | 0.92 (0.60, 1.43) | 0.722 | 0.00 | 0.57 |
Key: N, number of studies. P1 is an evaluation of the statistical significance level of the risk estimate, while P2 is an evaluation of the heterogeneity among included studies. Subgroup analyses were performed by study design (cohort or case-control) and data types of TSH levels. Three studies evaluating the relationship between TSH and dementia in men were analyzed separately.