Table 3.
Relative risks of hip and all fractures by quintiles of total vitamin A and retinol intake, Iowa Women's Health Study, 1986–1997
| Vitamin A quintiles |
Retinol quintiles |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1st | 2nd | 3rd | 4th | 5th | 1st | 2nd | 3rd | 4th | 5th | |
| Number | 6,940 | 6,941 | 6,940 | 6,942 | 6,940 | 6,940 | 6,941 | 6,941 | 6,941 | 6,940 |
| Intake, mean (IU) | 5,113 | 8,771 | 12,256 | 16,764 | 29,239 | 912 | 2,031 | 3,857 | 5,768 | 12,610 |
| Range (IU) | 221–7,055 | 7,056–10,484 | 10,485–14,209 | 14,210–19,892 | 19,893–236,991 | 28–1,405 | 1,406–2,952 | 2,953–4,655 | 4,656–7,001 | 7,002–211,051 |
| Hip fractures (n) | 93 | 122 | 102 | 99 | 119 | 109 | 84 | 116 | 101 | 125 |
| Person-years | 64,989 | 65,688 | 66,434 | 66,724 | 66,068 | 65,807 | 67,194 | 65,468 | 66,052 | 65,290 |
| Age-adjusted RR | 1.00 | 1.26 | 1.03 | 0.97 | 1.17 | 1.00 | 0.72 | 1.03 | 0.88 | 1.10 |
| (95% CI) | (0.96–1.65) | (0.78–1.37) | (0.73–1.29) | (0.89–1.54) | (0.54–0.96) | (0.79–1.33) | (0.67–1.15) | (0.85–1.42) | ||
| Test for trend (p) | 0.85 | 0.21 | ||||||||
| Multivariate-adjusteda RR | 1.00 | 1.27 | 1.08 | 1.02 | 1.25 | 1.00 | 0.69 | 1.03 | 0.86 | 1.10 |
| (95% CI) | (0.97–1.67) | (0.81–1.44) | (0.76–1.37) | (0.94–1.68) | (0.52–0.93) | (0.79–1.34) | (0.65–1.14) | (0.84–1.43) | ||
| Test for trend (p) | 0.49 | 0.19 | ||||||||
| All fractures | 1,298 | 1,319 | 1,256 | 1,311 | 1,319 | 1,324 | 1,238 | 1,346 | 1,270 | 1,324 |
| Person-years | 58,073 | 58,672 | 59,622 | 59,717 | 58,979 | 58,648 | 60,455 | 58,304 | 59,129 | 58,527 |
| Age-adjusted RR | 1.00 | 1.00 | 0.93 | 0.97 | 0.98 | 1.00 | 0.90 | 1.01 | 0.94 | 0.99 |
| (95% CI) | (0.92–1.06) | (0.86–1.01) | (0.89–1.04) | (0.91–1.06) | (0.83–0.97) | (0.94–1.09) | (0.87–1.01) | (0.91–1.06) | ||
| Test for trend (p) | 0.43 | 0.86 | ||||||||
| Multivariate-adjustedb RR | 1.00 | 0.98 | 0.92 | 0.94 | 0.95 | 1.00 | 0.89 | 1.00 | 0.92 | 0.96 |
| (95% CI) | (0.91–1.06) | (0.85–0.99) | (0.87–1.02) | (0.87–1.03) | (0.82–0.96) | (0.93–1.08) | (0.85–1.00) | (0.89–1.04) | ||
| Test for trend (p) | 0.098 | 0.61 | ||||||||
Adjusted for age (continuous), body mass index (continuous), waist-to-hip ratio (continuous), diabetes mellitus (yes, no), past irregular menstrual duration (yes, no), physical activity (moderate-high, low), steroid medication (current/prior, never), estrogen replacement (current/prior, never), and energy intake (continuous)
Adjusted for age (continuous), body mass index (continuous), diabetes mellitus (yes, no), cirrhosis (yes, no), past irregular menstrual duration (yes, no), thyrotropic medication (current/prior, never), sedative medication (current/prior, never), steroid medication (current/prior, never), antiepileptic medication (current/prior, never), diuretic medication (current/prior, never), education (less than or equal to high school, greater than high school), alcohol use (continuous), and energy intake (continuous)