The Bidirectional Association between Depressive Symptoms and Gait Speed: Evidence from the English Longitudinal Study of Ageing (ELSA)

Background

Depressive symptoms and physical performance are inversely associated, but it is unclear whether their association is bidirectional. We examined whether the association between depressive symptoms and physical performance measured using gait speed is bidirectional.

Methods

We used a national sample of 4,581 community-dwelling people aged 60 years and older from the English Longitudinal Study of Ageing (from 2002–03 to 2008-09). We fitted Generalized Estimating Equation (GEE) regression models to analyse repeated measurements of gait speed (m/sec) and elevated depressive symptoms (defined as a score of ≥4 on the eight-item Center for Epidemiological Studies-Depression scale).

Results

Slower gait speed was associated with elevated depressive symptoms both concurrently and two years later. After adjustment for previous depressive symptoms and sociodemographic, clinical, lifestyle, psychosocial, and cognitive factors the concurrent association was partially explained (Odds Ratio [OR] 0.42, 95% confidence interval [CI], 0.30 to 0.59, per 1m/sec increase in gait speed) and the two-year lagged association fully (OR 0.75, 95% CI, 0.56 to 1.00). Elevated depressive symptoms were associated with slower gait speed. Full adjustment for covariates (including previous gait speed) partially explained both the concurrent (β regression coefficient [β] -0.038, 95% CI, -0.050 to -0.026, for participants with elevated depressive symptoms compared with those with no or one symptom) and the two-year lagged associations (β -0.017, 95% CI, -0.030 to -0.005). Subthreshold depressive symptoms (defined as a score of two or three on the eight-item Center for Epidemiological Studies-Depression scale) were also associated with slower gait speed. Full adjustment for covariates partially explained both the concurrent (β -0.029, 95% CI, -0.039 to -0.019, for participants with subthreshold symptoms compared with those with no or one symptom) and the two-year lagged associations (β -0.011, 95% CI, -0.021 to -0.001).

Conclusions

The inverse association between gait speed and depressive symptoms appears to be bidirectional.     

Field investigation of innate immunity in passerine birds in suburban Chicago, Illinois, USA

The innate immune system is the first line of defense against pathogens, and it plays a fundamental role in coordinating a protective immune response in birds. Although many studies have evaluated avian immune responses in the laboratory, many fewer studies to date have done so in a field setting. To gain insight into interspecific differences in immune function in wild birds, we used a field-deployed in vitro microbicidal assay to measure constitutive innate immunity of whole blood collected from three common passerines in suburban Chicago, Illinois, in 2009. Data from one microbe, Escherichia coli 8739, revealed that American Robins (Turdus migratorius) had significantly lower bactericidal capacity than House Sparrows (Passer domesticus) or Gray Catbirds (Dumetella carolinensis). Bactericidal capacity for E. coli 8739 tended to be lower for birds infested with chewing lice than those without chewing lice, and male birds had lower microbicidal capacity than females in the case of Staphylococcus aureus. This study demonstrates the potential for field-deployable eco-immunologic tools to inform infectious disease ecology research.     

Wading through the swamp: what does tropical peatland restoration mean to national‐level stakeholders in Indonesia?

Ecological restoration is considered to play an important role in mitigating climate change, protecting biodiversity, and preventing environmental degradation. Yet, there are often multiple perspectives on what outcomes restoration should be aiming to achieve, and how we should get to that point. In this study we interview a range of policymakers, academics, and non‐governmental organization (NGO) representatives to explore the range of perspectives on the restoration of Indonesia's tropical peatlands—key global ecosystems that have undergone large‐scale degradation. Thematic analysis suggests that participants agreed about the importance of restoration, but had differing opinions on how effective restoration activities to date have been and what a restored peatland landscape should look like. These results exemplify how ecological restoration can mean different things to different people, but also highlight important areas of consensus for moving forward with peatland restoration strategies.