Predictors of depressive symptoms in older people--a survey of two general practice populations.

Background: Studies have shown strong associations between disability, social support and depressive symptoms in older people; but socio-economic effects are less clear and little is known about the role of health locus of control.

Objective: To examine the roles of physical health, disability, social support, socio-economic factors and health locus of control as predictors of depressive symptoms in older people.

Method: A postal survey of patients aged >/= 65 years from two London practices. Outcome measure was a score of > 5 on the 15-item Geriatric Depression Scale. Associations with other factors were examined using logistic regression and expressed as odds ratios.

Results: 70.4% (1602/2276) responded and provided Geriatric Depression Score 15 data, with 23.8% (381/1602) scoring > 5. After adjusting for age, sex and practice, high depression scores were associated with: (i) physical health and disability [e.g. severe versus no disability odds ratio 26.9 (15.7-46.2)]; (ii) social support [e.g. dissatisfaction with support odds ratio 4.2 (3.2-5.6)]; (iii) socio-economic [e.g. no occupational pension odds ratio 1.9 (1.5-2.4)]; (iv) health locus of control [e.g. internality 0.6 (0.6-0.7)]. After adjusting for disability, associations with general measures of physical health were reduced but still significant, while associations with social support, socio-economic factors, and health locus of control were unaffected. All four groups of factors were included in a final model for predicting depressive symptoms.

Conclusions: Disability, physical health, social support, socio-economic factors, and health locus of control were all independent depression score predictors in this study. This has implications for measures to reduce depressive symptoms in older people.