Severity of depressive symptoms as a predictor of mortality: the English longitudinal study of ageing.
BACKGROUND
Major depressive disorder and subthreshold depression have been associated with premature mortality. We investigated the association between depressive symptoms and mortality across the full continuum of severity.


METHODS
We used Cox proportional hazards models to examine the association between depressive symptom severity, assessed using the eight-item Center for Epidemiological Studies Depression Scale (CES-D; range 0-8), and the risk of all-cause mortality over a 9-year follow-up, in 11 104 members of the English Longitudinal Study of Ageing.


RESULTS
During follow-up, one fifth of study members died (N = 2267). Depressive symptoms were associated with increased mortality across the full range of severity (p trend < 0.001). Relative to study members with no symptoms, an increased risk of mortality was found in people with depressive symptoms of a low [hazard ratio (HR) for a score of 2 was 1.59, 95% confidence interval (CI) 1.40-1.82], moderate (score of 4: HR 1.80, 95% CI 1.52-2.13) and high (score of 8: HR 2.27, 95% CI 1.69-3.04) severity, suggesting risk emerges at low levels but plateaus thereafter. A third of participants (36.4%, 95% CI 35.5-37.3) reported depressive symptoms associated with an increased mortality risk. Adjustment for physical activity, physical illnesses, and impairments in physical and cognitive functioning attenuated this association (p trend = 0.25).


CONCLUSIONS
Depressive symptoms are associated with an increased mortality risk even at low levels of symptom severity. This association is explained by physical activity, physical illnesses, and impairments in physical and cognitive functioning.
School of Medicine,Cardiff University,Cardiff,UK.
J
J
White
Department of Epidemiology and Public Health,University College London,London,UK.
P
P
Zaninotto
Department of Primary Care and Population Health,University College London,London,UK.
K
K
Walters
Department of Epidemiology and Public Health,University College London,London,UK.
M
M
Kivimäki
Department of Epidemiology and Public Health,University College London,London,UK.
P
P
Demakakos
Department of Epidemiology and Public Health,University College London,London,UK.
A
A
Shankar
Institute for Social and Economic Research,University of Essex,Colchester,UK.
M
M
Kumari
School of Medicine,Cardiff University,Cardiff,UK.
J
J
Gallacher
Department of Epidemiology and Public Health,University College London,London,UK.
G D
GD
Batty
D000368:Aged; D000375:Aging / Q000523:psychology*; D002423:Cause of Death; D003863:Depression / Q000175:diagnosis* / Q000401:mortality*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors; D012720:Severity of Illness Index
Cohort study; depression; mortality