Table 3.
Fall outcomes by 3 definitions of achieved serum 25(OH)D concentration
| Level at 3 mo, ng/mL | Absolute change from BL to 3 mo (FU-BL), ng/mL) | Relative change from BL to 3 mo ((FU-BL)/BL), % | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ≤ 29 (N = 299) |
30-39 (N = 242) |
> 40 (N = 96) |
Lower 25%: -9 to 2 (N = 147) |
Middle 50%: 3-14 (N = 350) |
Upper 25%: 15-66 (N = 140) |
Lower 25%: -36 to 10 (N = 159) |
Middle 50%: 11-70 (N = 320) |
Upper 25%: 71-455 (N = 158) |
|
| First fall | |||||||||
| No. of events | 188 | 141 | 66 | 97 | 205 | 93 | 104 | 188 | 103 |
| No. of PYa | 240.3 | 209.2 | 80.7 | 102.6 | 305.5 | 122.1 | 112.5 | 281.5 | 136.3 |
| Rate per 100 PY | 78.2 | 67.4 | 81.8 | 94.5 | 67.1 | 76.2 | 92.5 | 66.8 | 75.6 |
| HRb, vs reference | Reference | 0.93 | 1.09 | Reference | 0.83 | 0.94 | Reference | 0.84 | 0.95 |
| 95% CIb | 0.74-1.16 | 0.82-1.46 | 0.64-1.06 | 0.70-1.26 | 0.66-1.08 | 0.71-1.27 | |||
| P, vs reference unadjustedb | 0.51 | 0.55 | 0.14 | 0.67 | 0.17 | 0.74 | |||
| P, overall unadjusted (adjusted)c | 0.55 (0.67) | 0.29 (0.60) | 0.34 (0.60) | ||||||
| First consequential falld | |||||||||
| No. of events | 133 | 106 | 55 | 67 | 152 | 75 | 71 | 143 | 80 |
| No. of PYa | 312.5 | 255.0 | 97.6 | 147.1 | 374.1 | 143.9 | 159.3 | 339.3 | 166.5 |
| Rate per 100 PY | 42.6 | 41.6 | 56.4 | 45.5 | 40.6 | 52.1 | 44.6 | 42.1 | 48.1 |
| HRb, vs reference | Reference | 1.02 | 1.38 | Reference | 0.99 | 1.28 | Reference | 1.05 | 1.20 |
| 95% CIb | 0.79-1.33 | 0.99-1.90 | 0.73-1.33 | 0.90-1.81 | 0.79-1.42 | 0.85-1.69 | |||
| P vs reference unadjustedb | 0.87 | 0.05 | 0.92 | 0.17 | 0.72 | 0.30 | |||
| P, overall unadjusted (adjusted)c | 0.15 (0.60) | 0.20 (0.60) | 0.56 (0.67) | ||||||
| All falls | |||||||||
| Total no. of eventse | 567 | 494 | 230 | 338 | 631 | 322 | 351 | 575 | 365 |
| Total no. of PYf | 466.4 | 380.4 | 167.2 | 223.5 | 550.0 | 240.5 | 239.7 | 506.6 | 267.7 |
| Rate per 100 PYg | 121.6 | 129.8 | 137.6 | 151.2 | 114.7 | 133.9 | 146.4 | 113.5 | 136.3 |
| Rate ratio vs referenceh | Reference | 1.12 | 1.15 | Reference | 0.75 | 0.93 | Reference | 0.78 | 0.94 |
| 95% CIh | 0.89-1.40 | 0.85-1.56 | 0.58-0.96 | 0.69-1.26 | 0.60-1.00 | 0.70-1.27 | |||
| P vs reference unadjustedh | 0.33 | 0.36 | 0.02 | 0.66 | 0.05 | 0.70 | |||
| P overall (unadjusted) adjustedi | 0.53 (0.67) | 0.05 (0.60) | 0.12 (0.60) | ||||||
| All consequential fallsd | |||||||||
| Total no. of eventse | 261 | 228 | 113 | 134 | 319 | 149 | 138 | 301 | 163 |
| Total no. of PYf | 466.4 | 380.4 | 167.2 | 223.5 | 550.0 | 240.5 | 239.7 | 506.6 | 267.7 |
| Rate per 100 PYg | 56.0 | 59.9 | 67.6 | 60.0 | 58.0 | 62.0 | 57.6 | 59.4 | 60.9 |
| Rate ratio vs referenceh | Reference | 1.15 | 1.24 | Reference | 0.99 | 1.08 | Reference | 1.07 | 1.05 |
| 95% CIh | 0.90-1.48 | 0.90-1.71 | 0.74-1.31 | 0.77-1.52 | 0.80-1.42 | 0.75-1.46 | |||
| P vs reference unadjustedh | 0.26 | 0.20 | 0.92 | 0.64 | 0.66 | 0.78 | |||
| P overall unadjusted (adjusted)i | 0.35 (0.60) | 0.81 (0.88) | 0.91 (0.91) |
To convert 25(OH)D ng/mL to nmol/L, multiply ng/mL by 2.5. These analyses include the 637 participants (92.6% of 688 randomized) who had serum 25(OH)D measured at the 3-month follow-up visit.
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BL, baseline; FU, follow-up; HR, hazard ratio; PY, person-years.
a For the first fall analysis, data from participants who did not fall were censored at their date of last contact for fall follow-up; for the first consequential fall analysis, data from participants who did not have a consequential fall were censored at their date of last contact for fall follow-up, with the exception that any participant who reported a fall that could not be categorized yes or no as to consequential was censored at that date if they had not previously reported a consequential fall. Thirteen participants who had not previously reported a consequential fall were censored at the date of their first fall that could not be categorized yes or no as to consequential.
b Each HR and its 95% CI were derived from a Cox proportional hazards regression model including serum 25(OH)D level group (2 indicator variables) and adjustment covariates (all at baseline) of age (continuous), race/ethnicity (other vs non-Hispanic White), sex (male vs female), education (more than high school vs high school or less), enrollment site location (Hagerstown vs Baltimore), Short Physical Performance Battery score (continuous), body mass index (continuous), and month of randomization as proxy for season (11 indicator variables); P vs reference tests whether the HR differs from 1 and is from the log-rank test and not adjusted for multiple comparisons.
c P overall is a 2 degrees of freedom analysis of variance for the overall effect of serum 25(OH)D group on time to first fall and tests whether the HRs differ. The Benjamini-Hochberg procedure was used to control the false discovery rate to less than 1/12 (1 out of the number of overall comparisons in the manuscript); an adjusted P value (shown in parentheses next to the unadjusted P) is statistically significant if < 0.08.
d A consequential fall is a fall that resulted in any injury or medical care sought.
e Fall counts have been top-coded at the value equal to the 99th percentile of nonzero fall counts.
f Observation time for a participant is the duration from randomization to date of last contact in the trial.
g Rate of all events is calculated as the total number of events summed across all participants divided by the total person-time observed summed across all participants.
h Each rate ratio, its 95% CI, and its P vs reference are derived from a negative binomial model with a term for treatment, an offset term for the participant’s observation time from randomization to date of last contact in the trial, and adjustment covariates as above. P vs reference is not adjusted for multiple comparisons.
i P overall is a 2 degree of freedom analysis of variance for the overall effect of serum 25(OH)D on total number of falls. The Benjamini-Hochberg procedure was used to control the false discovery rate to less than 1/12 (1 out of the number of overall comparisons in the manuscript); an adjusted P value (shown in parentheses next to the unadjusted P) is statistically significant if < 0.08.