shows demographic characteristics and depression marker levels for DPP participants at randomization. Among the 3,187 participants, 328 (10.3%) had BDI scores indicating at least mild depression (≥11), 86 (2.7%, data not shown) had BDI scores indicating moderate to severe depression (≥16), and 181 (5.7%) were taking antidepressant medicines. On entry to the study, only 29 (0.9%) DPP participants had both depression markers.
Depression symptoms and antidepressant medicine use of DPP participants by baseline characteristics
We found strong baseline associations between depression markers and all demographic factors except age (). At baseline, controlling for other demographic factors, men were less likely than women to have BDI scores ≥11 (P = 0.002), less likely to be taking antidepressant medicines (P < 0.0001), and less likely to have either depression marker (P < 0.0001). Participants with more education were less likely to have elevated BDI scores (P < 0.0001) and more likely to be taking antidepressants (P = 0.05). Race/ethnicity was associated with both elevated BDI scores (P = 0.0001) and antidepressant medicine use (P < 0.0001). Pairwise comparison (data not shown) found that non-Hispanic white participants were less likely to have elevated BDI scores than African-American, Hispanic-American, and American-Indian participants (P < 0.006) and more likely to take antidepressant medicines than those in any other racial/ethnic group (P < 0.004, except P < 0.05 compared with American Indians and Asians). Hispanic-American participants were more likely to take antidepressants than African-American participants (P = 0.01). At the end of study, 93% of participants remained active, and this was not associated with baseline depression marker status.
Changes in depression markers during the DPP
The proportion of DPP participants with BDI scores ≥11 decreased during the study (from 10.3% at baseline to 8.4% at year 3, P = 0.0016), whereas the proportion using antidepressant medicines increased (from 5.7% at baseline to 8.7% at year 3, P < 0.0001). The proportion of participants who had at least one of these two markers did not change significantly over time, reflecting the countervailing effects of the two component measures. These changes are shown by treatment arm in for both sexes. There was no significant interaction between DPP treatment arm and any of these time trends for either sex, indicating that the trends were similar for the three treatment arms, although at the 3rd year of follow-up there were marginally significant treatment arm differences in the proportion of female participants with either depression marker (P = 0.0635). The rate in the intensive lifestyle arm was lower than that in the placebo arm at that point (P < 0.02). In a separate analysis (data not shown), weight loss during the DPP was associated with a small but significant reduction in the risk of elevated depression (odds ratio [OR] 0.975/kg [95% CI 0.960–0.990], P = 0.002), and increased leisure activity was associated with a small but significant reduction in the risk of elevated symptoms (0.960/5 MET h/week [0.920–1.001], P = 0.012), a trend toward reduced antidepressant use (0.976/5 MET h/week [0.950 –1.002], P = 0.058), and a small but significant reduction in either marker (0.965/5 MET h/week [0.939 – 0.992], P = 0.002). There were no significant interactions between these trends and treatment arm.
Depression markers during the DPP by sex and treatment arm
shows changes in depression markers during the course of the DPP as a function of baseline depression marker status. shows that the majority (n = 2,707) of participants had neither marker at baseline; by the year 3 follow-up, ~5% of those participants had BDI scores ≥11, and a similar proportion were taking antidepressant medicines. Participants who had baseline BDI scores ≥11 () were more likely to start taking antidepressant medicines during the DPP than participants with lower baseline BDI scores (; OR 2.63, P < 0.0001). Most participants who had BDI scores ≥11 at baseline did not have elevated scores by the year 1 follow-up (), regardless of baseline antidepressant medicine use. Similarly, many participants who were taking antidepressant medicine at baseline were no longer taking it by the year 1 follow-up, regardless of baseline BDI score ().
Figure 1 Change in two depression markers (BDI ≥11 and taking antidepressant medicine) by baseline depression status. A: Participants who were negative for both depression markers at baseline. B: Participants with baseline BDI ≥11 who were not (more ...)
shows that during the DPP, antidepressant medicine use increased more among male than among female participants (P = 0.009). There were also significant interactions between trends in the proportion with either depression marker and both race/ethnicity (P < 0.0001) and education (P = 0.002). The proportion with either depression marker increased among non-Hispanic whites relative to other racial/ethnic groups and among those with ≥17 years of education relative to those with less education.
Figure 2 Time trend in depression markers by demographic factors sex (A), race/ethnicity (B), and education (C). Time trend in antidepressant medication varied by sex (A, P = 0.009). Time trend in either depression marker use varied by race/ethnicity (B, P < (more ...)