Table 1.

Demographic group differences

	Depressed (N=273)	Nondepressed (N=164)	Test Statistic	p Value
Age (y)	69.8 (6.3)	68.0 (6.5)	435 df, t = 2.86	0.0044
Sex (% women)	61.5% (168)	68.9% (113)	x2=2.42	0.1198
Race (% white)	82.1% (224)	84.1% (138)	x2 = 0.32	0.5738
Education (y)	14.4 (2.5)	15.5 (1.8)	416.94 df, t = 5.27	< 0.0001
Duration of Participation (months)	62.8 (44.4)	78.4 (56.3)	284.28 df, t = 3.08	0.0023
Self-Report of Medical Morbidity
Diabetes	15.0% (41)	5.5% (9)	x2 = 8.75	0.0031
Heart Disease	20.8% (57)	10.4% (17)	x2 = 7.96	0.0048
Hypertension	51.6% (141)	25.0% (41)	x2 = 29.78	< 0.0001
Cognitive Domain Z-Scores
Episodic Memory (N = 430)	N = 268 −0.05 (0.76)	N = 162 0.36 (0.61)	395.43 df, t = 6.26	< 0.0001
Psychomotor-Executive Function (N = 423)	N = 260 −0.04 (0.79)	N = 163 0.41 (0.51)	420.66 df, t = 7.22	< 0.0001
Verbal Fluency (N = 435)	N=271 −0.11 (0.85)	N = 164 0.41 (0.72)	389.07 df, t = 6.79	< 0.0001
Attention-Working Memory (N = 399)	N = 253 − 0.07 (0.81)	N = 146 0.22 (0.79)	397 df, t = 3.49	0.0005

All comparisons of categorical variables used chi-square tests with 1 degree of freedom, presented as percent (N). Comparison of continuous measures used pooled two-tailed t-tests, or Satterthwaite t-tests if variances were unequal, presented as mean (SD). Baseline cognitive data were missing for some participants, resulting in reduced sample sizes as presented. Cognitive domain data presented are z-transformed averages across multiple tests.