Objective sleep measures fail to predict depression
medwireNews: Poor self-reported sleep quality, but not objectively measured sleep quality, predicts future depression in older men, indicates a large, follow-up study.
The researchers found that associations between actigraphy-measured sleep disturbances - such as reduced sleep efficiency, prolonged sleep latency, greater nighttime wakefulness, and increased periods of long wakefulness - and future depression were largely explained by a greater burden of existing or pre-existing depressive symptoms.
"The clinical implications of our findings, both cross-sectional and longitudinal, suggest that older men presenting with reports of disturbed sleep should be evaluated for prevalent depressive symptoms and depression," say Misti Paudel (University of Minnesota-Twin Cities, Minneapolis, USA).
A total of 2510 nondepressed men aged 67 years or older participated in the study. Of these, 116 (4.6%) developed depression, with six or more depressive symptoms on the Geriatric Depression Scale (GDS), by an average of 3.4 years later.
The 41.4% of men who had poor self-reported sleep quality (Pittsburgh Sleep Quality Index score >5) at baseline had a significant 2.6-fold increased risk for developing depression. This increased risk was reduced after taking into account factors such as health status, education, use of antidepressants, and cognitive function, but remained significant at 1.53-fold.
Objectively measured sleep disturbances were also significantly associated with future depression when only age was adjusted for, with risk increasing 1.88-fold in the 9.8% of men with poor sleep efficiency (<70%), 1.77-fold in the 9.3% with prolonged sleep latency (≥1 hour), 1.48-fold in the 30.4% with increased nighttime wakefulness (≥1.5 hours), and 1.69-fold in the 31.2% with multiple long-wake episodes (≥8).
However, the results were attenuated and no longer significant for objectively measured sleep disturbances after the number of baseline depressive symptoms was taken into account.
It is possible that "depressive symptoms at baseline were attributable to sleep disturbances at baseline because the association between sleep and depression may be bidirectional in nature," the researchers comment in Sleep.
They also note a lack of linearity in the association between self-reported sleep quality and risk for depression at follow up.
"This suggests that a threshold rather than linear association exists between sleep quality and depression," they add.
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Lucy Piper, Senior medwireNews Reporter