Table 1.
Characteristics of included studies examining the association between β-carotene intake and risk of fractures
| Author, year | Study design | Sample size | Percent of Women | Fracture outcomes | Mean age | Exposure assessment | Covariate adjustmenta | Country | NOS score | Items that did not earn a NOS score |
|---|---|---|---|---|---|---|---|---|---|---|
| Feskanich, 2002 [24] | Cohort | 72,337 | 100 | Hip fracture | 60 | FFQ: Self-reported | 1, 7, 8, 14, 15, 16, 17, 18, 19, 20 | USA | 7 |
- Study controls for any additional factor - Complete follow up, all subjects accounted for |
| Zhang, 2006 [18] | C-C | 2564 | 69.2 | Hip fracture | 75.2 | FFQ: Self-reported | 1, 2, 8, 9, 11, 12, 14, 18, 19, 21 | USA | 9 | |
| Sahni, 2009 [17] | Cohort | 1046 | 61 | Hip fracture | 75 | FFQ: Self-reported | 1, 2, 8, 9, 12, 14, 19, 21, 22 | USA | 8 | - Truly representative of the average sample in the community |
| Ambrosini, 2013 [19] | Cohort | 2322 | 28.6 | Any fracture | 55 | Medical records | 1, 2, 6, 8, 14, 23 | Australia | 5 |
- Truly representative of the average sample in the community - Independent blind assessment - Study controls for any additional factor - Complete follow up, all subjects accounted for |
| Sun, 2014 [20] | C-C | 1452 | NA | Hip fracture | 70.5 | FFQ: Self-reported | 1,2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14 | China | 7 |
- Consecutive or representative series of cases - Community controls |
| Dai, 2014 [23] | Cohort | 63,154 | 55.8 | Hip fracture | 56.3 | FFQ: Self-reported | 1, 3, 8, 9, 11, 12, 14, 15, 24, 25, 26, 27, 28 | Singapore/China | 7 |
- Complete follow up, all subjects accounted for - Independent blind assessment |
| Jonge, 2015 [22] | Cohort | 5288 | 58.9 | Any fracture | 67 | FFQ: Self-reported | 1, 2, 3, 5, 8, 9, 11, 14, 29 | Netherland | 8 | - Selected an adequate follow up period for outcome of interest |
| Hayhoe, 2017 [37] | Cohort | 40,242 | 55.3 | Any/hip/spine fracture | 60.8 | 7-day food diaries | 1, 6, 7, 8, 9, 11, 12, 14, 15, 30, 31 | UK | 9 | |
| Cao, 2018 [21] | C-C | 2140 | 74.1 | Hip fracture | 70.6 | FFQ: Self-reported | 1, 3, 4, 5, 6, 7, 8, 10, 11, 12, 14, 32 | China | 5 |
- Consecutive or representative series of cases - Study controls for any additional factor - Same method of ascertainment for cases and controls - Same non-response rate for both groups |
Abbreviations: C-C case-control, FFQ food frequency questionnaire, NA not available, UK United Kingdomm, US United States,
aAge (1), sex (2), educational level (3), occupation (4), household income (5), family history of fracture (6), smoking status (7), alcohol intake (8), calcium use (9), multivitamin supplement use (10), physical activity (11), daily energy intake (12), dietary intake of selected nutrients (13), body mass index (14), use of postmenopausal hormones (15), hours of leisure-time activity (16), use of thiazide diuretics (17), protein use (18), vitamin D (19), vitamin K (20), caffeine use (21), height (22), medication use (23), dialect group (24), vitamin B6 (25), soy isoflavones (26), history of diabetes and stroke (27), use of hormone replacement therapy (28), disability index (29), hormone replacement therapy (30), corticosteroid use (31), and calcium supplement use (32)