Table 2.
ORs (95% CIs) for the chance of being cited, all types of publications included, N=110, n=5551
| Crude OR | Adjusted OR* | R2* | |
| Publication characteristics, content related | |||
| Type of exposure (ref: both siblings and infections) | 0.10 | ||
| Only no of siblings | 0.8 (0.6 to 1.1) | 0.5 (0.4 to 0.7) | |
| Only infection history | 1.3 (1.0 to 1.6) | 0.8 (0.6 to 1.1) | |
| Study outcome (ref: non-supportive results) | 0.11 | ||
| Mixed/unclear results | 1.2 (0.9 to 1.7) | 3.1 (2.2 to 4.5) | |
| Supportive results | 1.5 (1.1 to 2.0) | 2.2 (1.6 to 3.1) | |
| Publication type (empirical vs synthesis) | 4.3 (3.2 to 5.7) | 0.04 (crude) | |
| Study design (ref: cross-sectional) | 0.09 (crude) | ||
| Case–control | 1.4 (0.9 to 2.2) | ||
| Retrospective cohort | 0.9 (0.7 to 1.2) | ||
| Prospective cohort | 0.3 (0.2 to 0.5) | ||
| Narrative review | 0.1 (0.0 to 0.1) | ||
| Systematic review | 3.3 (1.8 to 5.8) | ||
| Editorial/other | 0.3 (0.2 to 0.4) | ||
| Sample size (ref: low, n=3517) | 0.02 | ||
| Medium | 1.6 (1.2 to 2.3) | 1.6 (1.0 to 2.6) | |
| High | 1.6 (1.2 to 2.3) | 1.9 (1.2 to 3.0) | |
| Specificity (ref: low) | 0.11 | ||
| Medium | 2.5 (1.5 to 4.0) | 2.7 (1.6 to 4.5) | |
| High | 8.8 (5.8 to 13.5) | 5.0 (3.1 to 7.9) | |
| Publication characteristics, not content related | |||
| Conclusive title (yes vs no) | 0.4 (0.3 to 0.7) | 0.3 (0.2 to 0.4) | 0.10 |
| Funding source (ref: exclusively non-profit) | 0.09 | ||
| Profit or both profit/non-profit | 0.9 (0.6 to 1.2) | 0.8 (0.6 to 1.2) | |
| Not reported | 0.4 (0.3 to 0.5) | 0.8 (0.6 to 1.0) | |
| No of authors (ref: 1–2) | 0.09 | ||
| 3–5 | 1.9 (1.4 to 2.5) | 1.0 (0.7 to 1.5) | |
| ≥6 | 3.6 (2.7 to 4.9) | 1.5 (1.0 to 2.4) | |
| No of affiliations (ref: 1) | 0.09 | ||
| 2 | 2.6 (2.0 to 3.5) | 1.8 (1.3 to 2.5) | |
| ≥3 | 2.1 (1.6 to 2.8) | 1.6 (1.1 to 2.2) | |
| No of references (ref: <30) | 0.09 | ||
| 30–50 | 1.1 (0.8 to 1.3) | 1.0 (0.8 to 1.2) | |
| ≥50 | 0.4 (0.3 to 0.6) | 0.8 (0.5 to 1.3) | |
| Journal characteristics | |||
| Journal impact factor (ref: 0–2, n=5033) | 0.11 | ||
| 2–4 | 3.4 (2.2 to 5.3) | 2.7 (1.7 to 4.2) | |
| ≥4 | 6.0 (4.0 to 9.2) | 4.9 (3.2 to 7.6) | |
| Author characteristics | |||
| Gender (female vs male, n=5392) | 0.8 (0.6 to 1.0) | 0.7 (0.6 to 1.0) | 0.09 |
| Continent (ref: Europe) | 0.11 | ||
| North America | 0.9 (0.6 to 1.3) | 0.9 (0.5 to 1.4) | |
| Asia | 0.3 (0.1 to 0.6) | 0.2 (0.1 to 0.3) | |
| Australia | 0.5 (0.3 to 0.8) | 0.5 (0.3 to 0.8) | |
| Type of Affiliation (other vs university) | 2.3 (1.8 to 2.9) | 2.0 (1.5 to 2.5) | 0.10 |
| Citation characteristics | |||
| Authority (ref: low) | 0.11 | ||
| Medium | 2.4 (1.8 to 3.3) | 1.8 (1.3 to 2.5) | |
| High | 3.7 (2.8 to 4.8) | 2.7 (2.0 to 3.7) | |
*Adjusted for study design. Bold odds ratios are statistically significant at p <0.05.
Supportive: supportive for Strachan’s original hygiene hypothesis, that is, inverse association between siblings/infections and allergy.
Non-supportive: no association or positive association between siblings/infections and allergy.
N, number of publications; n, number of potential citation paths.