TABLE 2.
Number of self-reported urinary tract stones by baseline demographic and dietary characteristics (annualized rate)1
| CaD group(n = 18,106) | Placebo group(n = 18,176) | HR2 (95% CI) | P for interaction3 | |
| n (%) | n (%) | |||
| All self-reported kidney stones | 449 (0.35) | 381 (0.30) | 1.17 (1.02, 1.34) | |
| Age group at screening | 0.194 | |||
| 50–59 y | 151 (0.30) | 140 (0.28) | 1.06 (0.84, 1.33) | |
| 60–69 y | 225 (0.39) | 168 (0.30) | 1.34 (1.10, 1.63) | |
| 70–79 y | 73 (0.34) | 73 (0.34) | 0.99 (0.72, 1.38) | |
| Ethnicity | 0.806 | |||
| White | 367 (0.34) | 302 (0.28) | 1.21 (1.04, 1.41) | |
| Black | 42 (0.36) | 38 (0.33) | 1.10 (0.71, 1.71) | |
| Hispanic | 23 (0.42) | 24 (0.49) | 0.90 (0.50, 1.62) | |
| American Indian | 4 (0.75) | 4 (0.79) | 0.84 (0.20, 3.61) | |
| Asian/Pacific Islander | 10 (0.40) | 8 (0.34) | 1.24 (0.49, 3.17) | |
| Unknown | 3 (0.21) | 5 (0.34) | 0.62 (0.14, 2.73) | |
| Education (collapsed category) | 0.088 | |||
| None–HS diploma/GED | 121 (0.40) | 86 (0.29) | 1.38 (1.05, 1.82) | |
| School after HS | 166 (0.33) | 170 (0.34) | 0.97 (0.78, 1.20) | |
| College degree or higher | 154 (0.33) | 122 (0.26) | 1.25 (0.99, 1.59) | |
| Baseline weight quartile | 126 (0.30) | 111 (0.26) | 1.17 (0.91, 1.52) | 0.866 |
| <67.8 kg | ||||
| 67.8–80.9 kg | 143 (0.33) | 122 (0.29) | 1.12 (0.88, 1.42) | |
| >80.9 kg | 180 (0.42) | 148 (0.35) | 1.22 (0.98, 1.52) | |
| BMI | 0.733 | |||
| <25 kg/m2 | 95 (0.28) | 81 (0.24) | 1.20 (0.89, 1.61) | |
| 25–30 kg/m2 | 153 (0.33) | 141 (0.31) | 1.08 (0.86, 1.35) | |
| >30 kg/m2 | 198 (0.41) | 158 (0.34) | 1.21 (0.99, 1.50) | |
| E alone (n = 1742) | 0.624 | |||
| E alone, active | 48 (0.45) | 37 (0.35) | 1.32 (0.82, 2.02) | |
| E alone, placebo | 42 (0.39) | 38 (0.35) | 1.13 (0.73, 1.75) | |
| E+P (n = 9913) | 0.337 | |||
| E+P, active | 63 (0.36) | 45 (0.26) | 1.41 (0.96, 2.07) | |
| E+P, placebo | 45 (0.26) | 40 (0.24) | 1.07 (0.70, 1.64) | |
| HT intervention (n = 11,655) | ||||
| HT, active | 111 (0.39) | 82 (0.29) | 1.37 (1.03, 1.82) | 0.293 |
| HT, placebo | 87 (0.31) | 78 (0.28) | 1.10 (0.81, 1.49) | |
| DM intervention (n = 25,210) | 0.587 | |||
| DM, intervention | 115 (0.34) | 98 (0.28) | 1.20 (0.91, 1.57) | |
| DM, control | 193 (0.35) | 175 (0.32) | 1.09 (0.88, 1.33) | |
| Thiazides (like) diuretic use | 0.708 | |||
| No | 423 (0.35) | 361 (0.30) | 1.16 (1.01, 1.34) | |
| Yes | 26 (0.43) | 20 (0.34) | 1.30 (0.72, 2.34) | |
| Regional solar irradiance | 0.943 | |||
| 475–500 Langley units | 99 (0.38) | 87 (0.33) | 1.12 (0.84, 1.49) | |
| 400–430 Langley units | 66 (0.30) | 50 (0.23) | 1.28 (0.88, 1.84) | |
| 375–380 Langley units | 53 (0.37) | 45 (0.32) | 1.15 (0.77, 1.71) | |
| 350 Langley units | 102 (0.37) | 82 (0.30) | 1.24 (0.92, 1.66) | |
| 300–325 Langley units | 129 (0.33) | 117 (0.30) | 1.10 (0.85, 1.41) | |
| Smoking | 0.422 | |||
| Never smoker | 234 (0.35) | 187 (0.28) | 1.26 (1.04, 1.53) | |
| Past smoker | 175 (0.34) | 162 (0.32) | 1.06 (0.86, 1.31) | |
| Current smoker | 29 (0.30) | 28 (0.30) | 0.99 (0.59, 1.67) | |
| Alcohol use | 0.945 | |||
| Not a current drinker | 139 (0.40) | 117 (0.33) | 1.19 (0.93, 1.53) | |
| <1 drink/wk | 170 (0.38) | 142 (0.32) | 1.16 (0.93, 1.45) | |
| ≥1 drink/wk | 135 (0.29) | 119 (0.26) | 1.13 (0.89, 1.45) | |
| Physical activity | 0.383 | |||
| >0–3.75 METs/wk | 142 (0.38) | 135 (0.36) | 1.03 (0.81, 1.31) | |
| >3.75–8.75 METs/wk | 150 (0.40) | 112 (0.30) | 1.33 (1.04, 1.70) | |
| >8.75–17.5 METs/wk | 118 (0.31) | 99 (0.26) | 1.18 (0.90, 1.54) | |
| n (%) | n (%) | |||
| HT use at WHI baseline | 0.351 | |||
| Never user | 221 (0.36) | 181 (0.30) | 1.20 (0.99, 1.46) | |
| Past user | 63 (0.28) | 65 (0.30) | 0.92 (0.65, 1.30) | |
| Current user | 163 (0.37) | 135 (0.30) | 1.23 (0.98, 1.55) | |
| HT use (self-report/intervention combination) | 0.207 | |||
| Never user | 142 (0.33) | 126 (0.30) | 1.10 (0.86, 1.40) | |
| Past user | 49 (0.27) | 52 (0.30) | 0.89 (0.60, 1.32) | |
| Current user | 257 (0.39) | 203 (0.30) | 1.29 (1.07, 1.55) | |
| Quartile of caffeine intake | 0.178 | |||
| <77.18 mg | 138 (0.43) | 131 (0.43) | 1.01 (0.79, 1.28) | |
| 77.18 to <177.50 mg | 108 (0.34) | 104 (0.33) | 1.04 (0.79, 1.36) | |
| 177.50 to <265.32 mg | 114 (0.35) | 78 (0.24) | 1.46 (1.10, 1.96) | |
| ≥265.32 mg | 89 (0.28) | 68 (0.21) | 1.34 (0.98, 1.84) | |
| Quartile of protein intake | 128 (0.40) | 96 (0.30) | 1.32 (1.01, 1.72) | 0.678 |
| <14.57% of energy | ||||
| 14.57 to <16.46% of energy | 99 (0.31) | 83 (0.26) | 1.22 (0.91, 1.64) | |
| 16.46 to <18.50% of energy | 107 (0.33) | 101 (0.32) | 1.04 (0.79, 1.37) | |
| ≥18.50% of energy | 115 (0.36) | 101 (0.32) | 1.14 (0.87, 1.49) | |
| Quartile of fat intake | 0.685 | |||
| <32.25% of energy | 101 (0.31) | 80 (0.26) | 1.24 (0.92, 1.66) | |
| 32.25 to <35.78% of energy | 94 (0.30) | 94 (0.29) | 1.01 (0.75, 1.34) | |
| 35.78 to <40.09% of energy | 130 (0.41) | 107 (0.34) | 1.22 (0.94, 1.57) | |
| ≥40.09 % of energy | 124 (0.39) | 100 (0.32) | 1.23 (0.94, 1.60) | |
| Quartile of dietary fat intake | 0.529 | |||
| <45.96 g | 117 (0.37) | 91 (0.29) | 1.27 (0.96, 1.67) | |
| 45.96 to <63.79 g | 96 (0.30) | 93 (0.29) | 1.04 (0.78, 1.38) | |
| 63.79 to <86.95 g | 103 (0.32) | 93 (0.30) | 1.07 (0.81, 1.42) | |
| ≥86.95 g | 133 (0.42) | 104 (0.32) | 1.31 (1.01, 1.69) | |
| Quartile of dietary sodium intake | 117 (0.37) | 97 (0.31) | 1.21 (0.92, 1.58) | 0.899 |
| <2010.04 mg | ||||
| 2010.04 to <2681.65 mg | 104 (0.32) | 94 (0.30) | 1.07 (0.81, 1.41) | |
| 2681.65 to <3514.06 mg | 107 (0.34) | 87 (0.27) | 1.24 (0.93, 1.64) | |
| ≥3514.06 mg | 121 (0.38) | 103 (0.32) | 1.19 (0.91, 1.54) | |
| Quartile of dietary potassium intake | 0.418 | |||
| <1902.56 mg | 125 (0.39) | 114 (0.37) | 1.06 (0.82, 1.37) | |
| 1902.56 to <2486.46 mg | 107 (0.34) | 87 (0.27) | 1.25 (0.94, 1.66) | |
| 2486.46 to <3161.51 mg | 112 (0.34) | 103 (0.33) | 1.06 (0.81, 1.39) | |
| ≥3161.51 mg | 105 (0.33) | 77 (0.24) | 1.41 (1.05, 1.89) | |
| Quartile of dietary iron intake | 0.895 | |||
| <8.77 mg | 114 (0.36) | 103 (0.33) | 1.09 (0.83, 1.42) | |
| 8.77 to <11.86 mg | 115 (0.36) | 100 (0.32) | 1.15 (0.88, 1.50) | |
| 11.86 to <15.53 mg | 104 (0.33) | 83 (0.26) | 1.25 (0.94, 1.67) | |
| ≥15.53 mg | 116 (0.36) | 95 (0.30) | 1.22 (0.93, 1.60) | |
| Quartile of dietary oxalic acid intake | 0.776 | |||
| <201.98 mg | 121 (0.38) | 112 (0.36) | 1.07 (0.83, 1.38) | |
| 201.98 to <276.35 mg | 115 (0.35) | 93 (0.30) | 1.17 (0.89, 1.55) | |
| 276.35 to <371.41 mg | 100 (0.31) | 87 (0.27) | 1.14 (0.86, 1.53) | |
| ≥371.41 mg | 113 (0.36) | 89 (0.28) | 1.30 (0.99, 1.72) | |
| Quartile of dietary vitamin C intake | 0.761 | |||
| <53.28 mg | 122 (0.38) | 97 (0.31) | 1.22 (0.94, 1.60) | |
| 53.28 to <84.68 mg | 128 (0.40) | 103 (0.32) | 1.22 (0.94, 1.59) | |
| 84.68 to <120.79 mg | 105 (0.33) | 103 (0.32) | 1.02 (0.78, 1.34) | |
| ≥120.79 mg | 94 (0.29) | 78 (0.25) | 1.22 (0.90, 1.64) | |
| Quartile of total calcium intake4 | 0.243 | |||
| <674.58 mg | 131 (0.41) | 98 (0.32) | 1.31 (1.01, 1.71) | |
| 674.58 to <1030.36 mg | 102 (0.32) | 102 (0.33) | 0.98 (0.74, 1.29) | |
| 1030.36 to <1490.12 mg | 117 (0.37) | 82 (0.26) | 1.41 (1.06, 1.87) | |
| ≥1490.12 mg | 93 (0.30) | 87 (0.28) | 1.12 (0.83, 1.50) | |
| n (%) | n (%) | |||
| Taking calcium as a single supplement | 0.741 | |||
| No | 374 (0.36) | 315 (0.30) | 1.18 (1.02, 1.37) | |
| Yes | 75 (0.31) | 66 (0.28) | 1.10 (0.79, 1.53) | |
| Quartile of total vitamin C intake5 | 0.982 | |||
| <77.33 mg | 124 (0.38) | 100 (0.31) | 1.21 (0.93, 1.57) | |
| 77.33 to <136.81 mg | 106 (0.33) | 93 (0.29) | 1.11 (0.84, 1.46) | |
| 136.81 to <356.65 mg | 102 (0.32) | 87 (0.27) | 1.19 (0.89, 1.58) | |
| ≥356.65 mg | 117 (0.37) | 101 (0.32) | 1.18 (0.90, 1.54) | |
| Quartile of total vitamin D intake5 | 121 (0.37) | 105 (0.33) | 1.11 (0.85, 1.44) | 0.397 |
| <3.25 μg | ||||
| 3.25 to <6.64 μg | 106 (0.33) | 103 (0.32) | 1.01 (0.77, 1.32) | |
| 6.64 to <13.28 μg | 109 (0.34) | 76 (0.24) | 1.42 (1.06, 1.91) | |
| ≥13.28 μg | 113 (0.37) | 97 (0.30) | 1.21 (0.92, 1.58) | |
| Quartile of total potassium intake5 | 122 (0.38) | 112 (0.36) | 1.06 (0.82, 1.37) | 0.281 |
| <1908.58 mg | ||||
| 1908.58 to <2495.70 mg | 109 (0.34) | 88 (0.27) | 1.25 (0.94, 1.66) | |
| 2495.70 to <3172.10 mg | 112 (0.34) | 106 (0.33) | 1.03 (0.79, 1.35) | |
| ≥3172.10 mg | 106 (0.33) | 75 (0.23) | 1.45 (1.08, 1.95) | |
| Quartile of total iron intake5 | 117 (0.36) | 109 (0.35) | 1.05 (0.81, 1.36) | 0.685 |
| <10.32 mg | ||||
| 10.32 to <15.67 mg | 106 (0.33) | 84 (0.26) | 1.25 (0.94, 1.67) | |
| 15.67 to <27.32 mg | 118 (0.37) | 92 (0.29) | 1.30 (0.99, 1.71) | |
| ≥27.32 mg | 108 (0.34) | 96 (0.30) | 1.15 (0.87, 1.52) | |
| History of kidney stone | 444 (0.35) | 372 (0.30) | 1.18 (1.03, 1.36) | 0.200 |
| No | ||||
| Yes | 5 (0.45) | 9 (0.73) | 0.58 (0.19, 1.75) |
1
CaD, calcium plus vitamin D; HS, high school; GED, general educational development; E, estrogen; P, progestin; HT, hormone therapy; WHI, Women's Health Initiative; DM, dietary modification; METs, metabolic equivalents; HR, hazard ratio.
2
From Cox proportional hazards regression models stratified according to age, DM participation, and history of kidney stone.
3
Test of linear trend for continuous variables. For categorical variables, P values for interaction from likelihood ratio test comparing models with and without interaction terms.
4
Combination of diet + supplements + medication.
5
Combination of diet + supplements.