CESD-R scores ranged from 0 to 45 with a median of 3.
Results were qualitatively similar in additional sensitivity analyses considering residential distance to roadway as a continuous variable on both the original scale and after taking the natural logarithm (data not shown), considering the presence of depressive symptoms defined as either a CESD-R score [greater than or equal to] 16 or reported use of antidepressant medication (resulting in an additional 61 participants being identified as having depressive symptoms; results not shown), considering CESD-R score as a linear continuous variable (Table 2; see also Supplemental Material, Table S1), or restricted to those participants with an MMSE > 24 (resulting in 21 fewer participants with CESD-R [greater than or equal to] 16; results not shown).
We found no evidence of a positive association between mean pollutant levels over the 2 weeks preceding CESD-R administration and presence of depressive symptoms (Table 4), although a statistically significant negative association was observed with [PM.sub.2.5] (OR = 0.67; 95% CI: 0.46, 0.98 per 3.4 [micro]g/[m.sup.3] increase).
In this cohort of community-dwelling older adults, the presence of depressive symptoms within the preceding 2 weeks, as assessed by the CESD-R, was not associated with markers of long-term exposure to traffic pollution.
Although both the SGDS and CESD-R are screening tools for depressive symptoms, the two instruments likely measure somewhat different aspects or components of depressive symptoms (Gerety et al.
Our study does not directly address this hypothesis because the CESD-R assesses the presence of depressive symptoms within the preceding 2 weeks rather than depression episodes or the presence of clinical depression.
Moreover, there were very few participants with CESD-R scores consistent with a probable depressive case as defined by Van Dam and Earleywine (2011), precluding our use of this outcome.