The impact of disability on depression among individuals with COPD.
BACKGROUND
Both disability and depression are common in COPD, but limited information is available on the time-ordered relationship between increases in disability and depression onset.


METHODS
Subjects were members of a longitudinal cohort with self-reported physician-diagnosed COPD, emphysema, or chronic bronchitis. Data were collected through three annual structured telephone interviews (T1, T2, and T3). Depression was defined as a score >/= 4 on the Geriatric Depression Scale Short Form (S-GDS). Disability was measured with the Valued Life Activities (VLA) scale; three disability scores were calculated: percent of VLAs unable to perform, percent of VLAs affected (unable to perform or with some degree of difficulty), and mean VLA difficulty rating. Disability increases were defined as a 0.5 SD increase in disability score between T1 and T2. Multiple logistic regression analyses estimated the risk of T3 depression following a T1 to T2 disability increase for the total cohort and then excluding individuals who met the depression criterion at T1 or T2.


RESULTS
Approximately 30% of subjects met the depression criterion each year. Eight percent to 19% experienced a T1 to T2 disability increase, depending on the disability measure. Including all cohort members and controlling for baseline S-GDS scores, T1 to T2 increases in disability yielded a significantly elevated risk of T3 depression (% affected odds ratio [OR] =3.6; 95% CI, [1.7, 7.7]; % unable OR = 6.1 [17, 21.8]; mean difficulty OR= 3.6 [1.7, 8.0]). Omitting individuals depressed at T1 or T2 yielded even stronger risk estimates for % unable (OR = 13.4 [2.0, 91.4]) and mean difficulty (OR = 3.9 [1.3, 11.8]).


CONCLUSIONS
Increases in VLA disability are strongly predictive of the onset of depression.
Katz
Patricia P
PP
University of California, San Francisco, 3333 California St, Ste 270, San Francisco, CA 94143-0920, USA. patti.katz@ucsf.edu
Julian
Laura J
LJ
Omachi
Theodore A
TA
Gregorich
Steven E
SE
Eisner
Mark D
MD
Yelin
Edward H
EH
Blanc
Paul D
PD
D000203:Activities of Daily Living / Q000523:psychology; D000368:Aged; D015331:Cohort Studies; D003863:Depression / Q000453:epidemiology* / Q000523:psychology*; D006233:Persons with Disabilities / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006801:Humans; D007407:Interviews as Topic; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000523:psychology*; D012650:Self Disclosure