Abstract
Both morbidity and mortality are elevated for individuals with subsyndromal depression (SSD) compared to non-depression (ND) in those of younger ages, but scientific studies are scarce for very old individuals. The aim of this study was therefore to compare the morbidity and mortality in very old individuals with SSD and ND. An 8-year prospective population-based study was undertaken on 85-year-old individuals in Sweden. Data were collected from postal questionnaires and clinical assessments at baseline, after 1, 5, and 8 years. Depressive symptoms were measured with Geriatric Depression Scale and the results were classified into ND, SSD, and syndromal depression. Mortality was investigated using multivariable cox regressions, and variables of morbidity were investigated using linear mixed models. Compared to ND, in people with SSD, mortality was elevated in the univariate regression, but this association vanished when controlling for relevant covariates. Morbidity was elevated with regard to basic activities of daily living (ADLs), instrumental ADLs, loneliness, self-perceived health, and depressive symptoms for individuals with SSD compared to ND, whereas cognitive speed, executive functions, and global cognitive function were not significantly impaired when adjusting for covariates. SSD among very old individuals is longitudinally associated with elevated morbidity but not mortality, when controlling for relevant covariates. Considering the high prevalence of SSD and the demographic development of increasing numbers of very old people, the findings highlight the need to develop clinical and societal strategies to prevent SSD and associated negative outcomes.
Highlights
Subsyndromal depression (SSD) or subthreshold depression is a common affective condition that has received increasing attention in the literature during the last decade
SSD among very old individuals is longitudinally associated with elevated morbidity but not mortality, when controlling for relevant covariates
SSD compared with non-depression (ND) in old individuals is longitudinally associated with impaired activities of daily living (ADLs; Barry et al, 2009) and cognitive function (Han et al, 2008), reduced self-perceived health (Callahan et al, 1994), worse psychiatric outcomes with higher risk of major depression (Beekman et al, 2002), and higher mortality (Cuijpers et al, 2013)
Summary
Subsyndromal depression (SSD) or subthreshold depression is a common affective condition that has received increasing attention in the literature during the last decade. SSD is generally associated with lower degrees of impairment and suffering (Ayuso-Mateos et al, 2010), but the relevance of SSD is substantial because of a higher prevalence in the population (Meeks et al, 2011), and for example, the population-attributable fraction of mortality is comparable between the two (Cuijpers et al, 2013). As affective conditions vary greatly in intensity over time, longitudinal studies of depressive symptoms have certain advantages for their understanding. SSD compared with non-depression (ND) in old individuals is longitudinally associated with impaired activities of daily living (ADLs; Barry et al, 2009) and cognitive function (Han et al, 2008), reduced self-perceived health (Callahan et al, 1994), worse psychiatric outcomes with higher risk of major depression (Beekman et al, 2002), and higher mortality (Cuijpers et al, 2013).
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