Pain severity as a mediator of the association between depressive symptoms and physical performance in knee osteoarthritis.

OBJECTIVE: Depressive symptoms in knee osteoarthritis (OA) are associated with increased pain severity and declines in physical performance. This study examined whether pain severity mediates the association between depressive symptoms and physical performance in persons with radiographic knee OA. METHOD: Three years of annual data from participants (n = 1,463) with radiographic knee OA in the Osteoarthritis Initiative (OAI) were analyzed. Depressive symptoms were measured using the Center for Epidemiological Studies Depression (CES-D) scale. Pain severity was evaluated with the Western Ontario and McMaster Universities Arthritis Index. Physical performance was assessed via standardized gait speed. Marginal structural models were used to assess the direct (unmediated) effects of depressive symptoms on physical performance and indirect (mediated) effects through pain severity. RESULTS: Direct and indirect effects for a difference in CES-D score of 0-1 were -0.0051 (95% confidence intervals (CI): -0.0053, -0.0049) and -0.0016 (95% CI: -0.0024, -0.0007) standard deviations in gait speed, respectively. Higher depressive symptom severity exhibited diminishing, incremental, direct and indirect effects and for a difference in CES-D score of 15-16 were -0.0045 (95% CI: -0.0047, -0.0042) and -0.0009 (95% CI: -0.0014, -0.0004) standard deviations in gait speed, respectively. Therefore, the magnitude of the mediated, indirect effect, was never larger than 24%. CONCLUSION: Pain severity mediated approximately one-fifth of the association between depressive symptoms and physical performance in persons with radiographic knee OA, and the diminishing incremental effects may explain why unimodal treatment strategies with a single disease target are often ineffective in depressed OA patients.

Effects of a common insecticide on wetland communities with varying quality of leaf litter inputs.

Chemical contamination of aquatic systems often co-occurs with dramatic changes in surrounding terrestrial vegetation. Plant leaf litter serves as a crucial resource input to many freshwater systems, and changes in litter species composition can alter the attributes of freshwater communities. However, little is known how variation in litter inputs interacts with chemical contaminants. We investigated the ecological effects resulting from changes in tree leaf litter inputs to freshwater communities, and how those changes might interact with the timing of insecticide contamination. Using the common insecticide malathion, we hypothesized that inputs of nutrient-rich and labile leaf litter (e.g., elm [Ulmus spp.] or maple [Acer spp.]) would reduce the negative effects of insecticides on wetland communities relative to inputs of recalcitrant litter (e.g., oak [Quercus spp.]). We exposed artificial wetland communities to a factorial combination of three litter species treatments (elm, maple, and oak) and four insecticide treatments (no insecticide, small weekly doses of 10 µg L-1, and either early or late large doses of 50 µg L-1). Communities consisted of microbes, algae, snails, amphipods, zooplankton, and two species of tadpoles. After two months, we found that maple and elm litter generally induced greater primary and secondary production. Insecticides induced a reduction in the abundance of amphipods and some zooplankton species, and increased phytoplankton. In addition, we found interactive effects of litter species and insecticide treatments on amphibian responses, although specific effects depended on application regime. Specifically, with the addition of insecticide, elm and maple litter induced a reduction in gray tree frog survival, oak and elm litter delayed tree frog metamorphosis, and oak and maple litter reduced green frog tadpole mass. Our results suggest that attention to local forest composition, as well as the timing of pesticide application might help ameliorate the harmful effects of pesticides observed in freshwater systems.

[Assessment of pain in advanced dementia. Construct validity of the German PAINAD]. / Beurteilung von Schmerz bei Demenz (BESD). Untersuchung zur Validität eines Verfahrens zur Beobachtung des Schmerzverhaltens.

BACKGROUND: The observation scale PAINAD (pain assessment in advanced dementia) is composed of five behavioral categories: breathing, vocalization, facial expression, body language, and consolability. The present study investigates the construct validity of the German version. PATIENTS AND METHODS: We conducted a prospective one-dimensional observation study with repeated measurements (t(1)=pretreatment, t(2)=2 h posttreatment, t(3)=24 h posttreatment). The sample consisted of 12 verbally noncommunicative demented inpatients with severe comorbidity treated in three geriatric clinics. Their age was M=84.3 years (SD=4.4) on the average. Ten of them were female. Inclusion criteria were pain-related physical illness and observed pain behavior. Every patient was treated with analgesics after t(1). After t(2) the medication was discontinued in five patients until t(3). Nurses documented the PAINAD scores after an observation period of 2 min during routine care. RESULTS: Pain behavior at t(2) diminished considerably displaying a large effect size. Scores continued to be low at t(3) only in the sample with continued medication. Scores in the other part of the sample returned to initial values. CONCLUSION: The data demonstrate that pain medication strongly impacts the pain behavior of demented patients. The outcome supports the assumption that PAINAD really measures pain.