Citation* | Sample size | Population based/ random sample | Location | Children (<18 years) | Adults (18–64 years) | Older adults (≥65 years) |
Brown9 | 249 405 | Yes | USA | + | ||
Cherrie63 | 281 | Yes | UK | N | N | + |
Cherrie64 | 281 | Yes | UK | +N | ||
Clarke53 | 949 | Yes | USA | N | N | |
Dadvand65 | 2593 | No | Spain | +N | ||
Dadvand54 | 987 | Yes | Spain | +N | ||
Dadvand66 | 253 | No | Spain | +N | ||
Dzhambov72 | 112 | No | Bulgaria | +N | ||
de Keijzer55 | 6506 | Yes | UK | +N | +N | |
Flouri56 | 4758 | Yes | UK | + | ||
Hystad57 | 6658 | Yes | Canada | - N | ||
Kuhn73 | 341 | No | Germany | +N | ||
Liao67 | 1312 | No | China | + | ||
Reuben68 | 1658 | Yes | UK | N | ||
Wang69 | 3544 | No | China | N | ||
Ward70 | 72 | No | New Zealand | N | ||
Wu59 | 2424 | Yes | UK | – | ||
Wu58 | 7505 | Yes | UK | - N | ||
Yu71 | 3240 | No | China | N | ||
Yuchi60 | 678 000 | Yes | Canada | + - | + - | |
Zhu61 | 6994 | Yes | China | + | ||
Zijlema62 | 1628 | Yes | Spain, UK, Netherlands | +N | +N | |
Studies with positive associations | 5 | 4 | 8 | |||
Studies with inverse associations | 0 | 2 | 3 | |||
Studies with null associations | 6 | 6 | 8 | |||
Total studies | 8 | 7 | 13 |
*Full list of papers found in online supplemental text 1.
+, positive association; -, inverse association; N, null association.