Table 2.
Characteristics of articles cited as evidence to support vitamin D and/or Ca recommendations in forty-seven bone health guidelines
| All (n 156) | Articles on vitamin D/Ca supplements (n 103) | |||
|---|---|---|---|---|
| n | % | n | % | |
| Publication year | ||||
| 1985–2009 | 85 | 54·5 | 58 | 56·3 |
| 2010–2018 | 71 | 45·5 | 45 | 43·7 |
| Journal 5-year impact factor* | ||||
| Low: 3·485 (3·285–3·917) | 51 | 32·7 | 27 | 26·2 |
| Medium: 5·985 (5·879–7·831) | 52 | 33·3 | 30 | 29·1 |
| High: 27·997 (19·658–59·245) | 53 | 34·0 | 46 | 44·7 |
| Frequency of citations* | ||||
| Low: Tertile 1: 34·5 (19–53) | 52 | 33·3 | 34 | 33·0 |
| Medium: Tertile 2: 138 (105–192) | 52 | 33·3 | 35 | 34·0 |
| High: Tertile 3: 523·5 (338·5–851·2) | 52 | 33·3 | 34 | 33·0 |
| Study design | ||||
| RCT | 49 | 31·4 | 44 | 43·6 |
| Non-randomised trial | 2 | 1·3 | 1 | 0·99 |
| Cohort study | 19 | 12·2 | 7 | 6·9 |
| Cross-sectional study | 18 | 11·5 | 6 | 5·9 |
| Case control study | 1 | 0·6 | 1 | 0·99 |
| Systematic review of RCT | 36 | 25 | 32 | 31·1 |
| Systematic review of non-RCT | 3 | 1·9 | 1 | 0·99 |
| Commentary/editorial/narrative review | 28 | 17·9 | 11 | 10·7 |
| Funding disclosure | ||||
| Missing | 29 | 18·6 | 15 | 14·6 |
| Yes, disclosed funding sources | 120 | 76·9 | 85 | 82·5 |
| Yes, disclosed no funding | 4 | 2·6 | 3 | 2·9 |
| Unclear | 3 | 1·9 | 0 | |
| COI disclosure | ||||
| No (explicitly stating no COI) | 62 | 39·7 | 37 | 35·9 |
| Missing COI declaration | 49 | 31·4 | 35 | 34·0 |
| Unclear | 2 | 1·3 | 2 | 1·9 |
| Declared COI in at least one author | 43 | 27·6 | 29 | 28·2 |
RCT, randomised control trial; COI, conflicts of interest.
*
Tertiles are expressed as median (interquartile range).