Is later-life depression a risk factor for Alzheimer's disease or a prodromal symptom: a study using post-mortem human brain tissue?

BACKGROUND: Depression and dementia are both common diseases. Although new cases of depression are more common in younger adults, there is a second peak at the age of 50 years suggesting a different pathological process. Late-life depression (LLD) is associated with dementia. However, it remains unclear whether depression represents a dementia prodrome or is a true risk factor for its development. LLD is thought to have a vascular component and this may be a possible link between depression and dementia. We hypothesised that later-life depression is a prodromal manifestation of dementia and would therefore be associated with more AD, and/or ischaemic brain abnormalities that are present in earlier-life depression or in age- and sex-matched controls. METHODS: We assessed post-mortem orbitofrontal cortex and dorsolateral pre-frontal cortex from 145 individuals in 4 groups: 28 18-50-year-olds with depression, 30 older individuals (ages 51-90) with depression, 28 with early AD (Braak tangle stages III-IV) and 57 matched controls (17 early-life, 42 later-life). Levels of Aß, phospho-tau and α-synuclein were assessed by immunohistochemistry and ELISA. To quantify chronic ischaemia, VEGF, MAG and PLP1 were measured by ELISA. To assess pericyte damage, PDGFRB was measured by ELISA. For blood-brain barrier leakiness, JAM-A, claudin 5 and fibrinogen were measured by ELISA. To quantity endothelial activation, the ratio of ICAM1:collagen IV was assessed by immunohistochemistry. RESULTS: There was no evidence of chronic cerebral hypoperfusion or increased Aß/tau in either depression group. There was also no indication of pericyte damage, increased blood-brain barrier leakiness or endothelial activation in the OFC or DLPFC in the depression groups. CONCLUSIONS: Contrary to some previous findings, we have not found evidence of impaired vascular function or increased Aß in LLD. Our study had a relatively small sample size and limitations in the availability of clinical data. These results suggest that depression is a risk factor for dementia rather than an early manifestation of AD or a consequence of cerebral vascular insufficiency.

Masks for prevention of respiratory viruses on the BMT unit: results of a quality initiative.

Respiratory viral infections (RVI) cause significant morbidity and mortality in hospitalized oncology patients. These viruses are easily spread from asymptomatic and/or symptomatic healthcare workers and visitors to immunocompromised patients, and literature review of facemasks for prevention of infection revealed mixed results. The Bone Marrow Transplant (BMT) Quality Assurance (QA) Committee at Mount Sinai began a surgical mask initiative on the BMT unit. The purpose of our initiative was to assess the impact of surgical mask implementation for healthcare workers and visitors on nosocomial RVI in all patients hospitalized on the BMT unit. We hypothesized that implementing surgical masks would reduce the number of hospital-acquired RVI. We performed a retrospective study involving all patients with malignancy hospitalized on the BMT unit for 4 years. During the latter 2 years, all healthcare workers and visitors were required to wear a surgical mask in every patient room on the BMT unit. Primary endpoint was incidence of RVI after implementation of surgical masks. The 2-year incidence of RVI in the pre-mask period was 14 out of a total of 15 001 patient days on the unit vs 2 out of 15 608 patient days after mask implementation. The difference in incidence of RVI within the two time intervals was noted to be statistically significant (P<.05, 2-proportion z-test). Our quality initiative demonstrated that surgical masks are an infection control modality that may provide benefit to oncology/BMT units by decreasing the risk for hospital-acquired RVI.