Table 2. Adjusted Mean Scores for the 8-Item Patient Health Questionnaire Depression Scale (PHQ-8) at Each Year Since Randomization Compared With Baseline.
| Vitamin D3 | Placebo | Between-group difference for mean change in PHQ-8 score (95% CI)b | P value | P for interactionc | |||
|---|---|---|---|---|---|---|---|
| No. of participants | Adjusted mean PHQ-8 score (95% CI)a | No. of participants | Adjusted mean PHQ-8 score (95% CI)a | ||||
| At baseline | 9181 | 1.08 (1.05 to 1.11) | 9172 | 1.13 (1.09 to 1.16) | |||
| 1 y vs baseline | 8534 | 0.03 (−0.01 to 0.07) | 8486 | 0.03 (0 to 0.07) | −0.01 (−0.06 to 0.05) | .84 | .71 |
| 2 y vs baseline | 8381 | 0.07 (0.03 to 0.11) | 8344 | 0.04 (0 to 0.08) | 0.03 (−0.03 to 0.08) | .35 | |
| 3 y vs baseline | 8176 | 0.09 (0.05 to 0.13) | 8112 | 0.07 (0.03 to 0.12) | 0.01 (−0.04 to 0.07) | .63 | |
| 4 y vs baseline | 7763 | 0.06 (0.02 to 0.10) | 7603 | 0.07 (0.03 to 0.11) | −0.01 (−0.07 to 0.05) | .73 | |
| 5 y vs baseline | 5316 | 0.20 (0.15 to 0.25) | 5231 | 0.16 (0.11 to 0.22) | 0.03 (−0.04 to 0.10) | .40 | |
| Overall | 9181 | 9172 | 0.01 (−0.04 to 0.05)d | .72 | |||
a
From general linear models of response profiles to estimate the means, with time modeled as indicator variables; models were controlled for age, sex, and fish oil randomization group. The repeated-measures model used all available responses and can handle missing outcome data, which were assumed to be missing at random.
b
From the repeated-measures model (primary outcome).
c
Calculated using 5 degrees of freedom for the treatment × time interaction term in the model.
d
Averaged across all follow-up years (1-5 years) from the repeated-measures model; all participants contributed data to the repeated-measures analysis at 1 or more times.