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| First author | Year | Type of study | Sample size | Mean (minutes) | City | Score of quality |
| Mosadegh rad | 2004 | Cross-sectional | 1336 | 4.34 | Ghazvin | 14 |
| Khori | 2012 | Cross-sectional | 620 | 6.9 | Gorgan | 15 |
| Mohebbifar | 2014 | Cross-sectional | 160 | NA | Ghazvin | 19 |
| Hasanpoor | 2015 | Cross-sectional | 428 | 4.67 | Ghazvin | 16 |
| Faraji Khiavi | 2016 | Cross-sectional | 550 | NA | Ahvaz | 20 |
| Janati | 2017 | Cross-sectional | 540 | 8.25 | Tabriz | 19 |
