Table 2.
Summary characteristic of included studies
| Journal | Recent | Previous | ||
|---|---|---|---|---|
| Annals of Internal Medicine | 9 | 17% | 54 | 22% |
| British Medical Journal | 24 | 46% | 117 | 48% |
| JAMA | 7 | 13% | 32 | 13% |
| New England Journal of Medicine | 1 | 2% | 9 | 4% |
| PLOS Medicine | 5 | 10% | 12 | 5% |
| The Lancet | 6 | 12% | 18 | 7% |
| Total: | 52 | 242 | ||
| Mean AMSTAR score for recent meta-analyses | 8.5 (SD 1.5) | |||
| Mean impact factor for previous studies | 7.7 (SD 8.8) | |||
| Previous SRs with meta-analysis | 218 | |||
| Previous SRs without meta-analysis | 24 | |||
| Number of previous studies for a recent meta-analysis | 0 to 28 (mean 4.65; SD 4.65) | |||
| Mean length of time from publication year previous to recent study | 3.6 years (SD 2.5) | |||
| Mean similarity score between previous and recent studies | 1.8 points (SD 1.1, range 0 to 4) | |||