Table 1.
Frequency of studies by study design and research area (n = 202)
| Characteristic | n | (%) |
|---|---|---|
| Study designs1 | ||
| Case-reports | 44 | (21.8%) |
| Case-series | 28 | (13.9%) |
| Randomized controlled trials | 4 | (2.0%) |
| Observational | 105 | (52.0%) |
| Cross-sectional | 84 | (41.6%) |
| Cohort/longitudinal | 21 | (10.4%) |
| Qualitative | 18 | (8.9%) |
| Mixed methods2 | 2 | (1.0%) |
| Meta-analysis | 1 | (0.5%) |
| Research areas3 | ||
| Health effects | 93 | (46.0%) |
| Etiology | 49 | (24.3%) |
| Epidemiology | 50 | (24.8%) |
| Regulatory policy | 17 | (8.4%) |
| Marketing/advertising | 11 | (5.5%) |
1Categories are mutually exclusive. 2Mixed methods studies were cross-sectional + case series and longitudinal + qualitative. 3Categories are mutually inclusive