Wide-Band, High-Quantum-Efficiency Photodetector

A design has been proposed for a photodetector that would exhibit a high quantum efficiency (as much as 90 percent) over a wide wavelength band, which would typically be centered at a wavelength of 1.55 m. This and similar photodetectors would afford a capability for detecting single photons - a capability that is needed for research in quantum optics as well as for the practical development of secure optical communication systems for distribution of quantum cryptographic keys. The proposed photodetector would be of the hot-electron, phonon-cooled, thin-film superconductor type. The superconducting film in this device would be a meandering strip of niobium nitride. In the proposed photodetector, the quantum efficiency would be increased through incorporation of optiA design has been proposed for a photodetector that would exhibit a high quantum efficiency (as much as 90 percent) over a wide wavelength band, which would typically be centered at a wavelength of 1.55 m. This and similar photodetectors would afford a capability for detecting single photons - a capability that is needed for research in quantum optics as well as for the practical development of secure optical communication systems for distribution of quantum cryptographic keys. The proposed photodetector would be of the hot-electron, phonon-cooled, thin-film superconductor type. The superconducting film in this device would be a meandering strip of niobium nitride. In the proposed photodetector, the quantum efficiency would be increased through incorporation of opti

The Relation of Patient Dependence to Home Health Aide Use in Alzheimer's Disease

BACKGROUND: Although there has been much research devoted to understanding the predictors of nursing home placement (NHP) in Alzheimer's disease (AD) patients, there is currently a lack of research concerning the predictors of home health care. The objective of this study was to examine whether the Dependence Scale can predict home health aide (HHA) use. METHODS: The sample is drawn from the Predictors Study, a large, multicenter cohort of patients with probable AD, prospectively followed annually for up to 7 years in three university-based AD centers in the United States. Markov analyses (n=75) were used to calculate annual transition probabilities for the "new onset" of HHA use (instances where an HHA was absent at the previous visit, but present at the next visit) as a function of HHA presence at the preceding year's visit and dependence level at that preceding year's visit. RESULTS: The dependence level at the previous year's visit was a significant predictor of HHA use at the next year's visit. Three specific items of the Dependence Scale (needing household chores done for oneself, needing to be watched or kept company when awake, and needing to be escorted when outside) were significant predictors of the presence of an HHA. CONCLUSION: The Dependence Scale is a valuable tool for predicting HHA use in AD patients. Obtaining a better understanding of home health care in AD patients may help delay NHP and have a positive impact on the health and well-being of both the caregiver and the patient

Change in Body Mass Index before and after Alzheimer's Disease Onset

OBJECTIVES: A high body mass index (BMI) in middle-age or a decrease in BMI at late-age has been considered a predictor for the development of Alzheimer's disease (AD). However, little is known about the BMI change close to or after AD onset. METHODS: BMI of participants from three cohorts, the Washington Heights and Inwood Columbia Aging Project (WHICAP; population-based) and the Predictors Study (clinic-based), and National Alzheimer's Coordinating Center (NACC; clinic-based) were analyzed longitudinally. We used generalized estimating equations to test whether there were significant changes of BMI over time, adjusting for age, sex, education, race, and research center. Stratification analyses were run to determine whether BMI changes depended on baseline BMI status. RESULTS: BMI declined over time up to AD clinical onset, with an annual decrease of 0.21 (p=0.02) in WHICAP and 0.18 (p=0.04) kg/m2 in NACC. After clinical onset of AD, there was no significant decrease of BMI. BMI even increased (b=0.11, p=0.004) among prevalent AD participants in NACC. During the prodromal period, BMI decreased over time in overweight (BMI>/=25 and /=30) NACC participants. After AD onset, BMI tended to increase in underweight/normal weight (BMI<25) patients and decrease in obese patients in all three cohorts, although the results were significant in NACC study only. CONCLUSIONS: Our study suggests that while BMI declines before the clinical AD onset, it levels off after clinical AD onset, and might even increase in prevalent AD. The pattern of BMI change may also depend on the initial BMI

Clinical Characteristics and Longitudinal Changes of Informal Cost of Alzheimer's Disease in the Community

Most estimates of the cost of informal caregiving in patients with Alzheimer's disease (AD) remain cross-sectional. Longitudinal estimates of informal caregiving hours and costs are less frequent and are from assessments covering only short periods of time. The objectives of this study were to estimate long-term trajectories of the use and cost of informal caregiving for patients with AD and the effects of patient characteristics on the use and cost of informal caregiving. The sample is drawn from the Predictors Study, a large, multicenter cohort of patients with probable AD, prospectively followed annually for up to 7 years in three university-based AD centers in the United States (n=170). Generalized linear mixed models were used to estimate the effects of patient characteristics on use and cost of informal caregiving. Patients' clinical characteristics included cognitive status (Mini-Mental State Examination), functional capacity (Blessed Dementia Rating Scale (BDRS)), comorbidities, psychotic symptoms, behavioral problems, depressive symptoms, and extrapyramidal signs. Results show that rates of informal care use and caregiving hours (and costs) increased substantially over time but were related differently to patients' characteristics. Use of informal care was significantly associated with worse cognition, worse function, and higher comorbidities. Conditional on receiving informal care, informal caregiving hours (and costs) were mainly associated with worse function. Each additional point on the BDRS increased informal caregiving costs 5.4%. Average annual informal cost was estimated at $25,381 per patient, increasing from$20,589 at baseline to $43,030 in Year 4

Home Health and Informal Care Utilization and Costs over Time in Alzheimer's Disease

OBJECTIVES: To (1) compare home health and informal (unpaid) services utilization among patients with Alzheimer's disease (AD), (2) examine longitudinal changes in services use, and (3) estimate possible interdependence of home health and informal care utilization. METHODS: The sample is drawn from the Predictors Study, a large, multicenter cohort of patients with probable AD, prospectively followed annually for up to 7 years in three university-based AD centers. Bivariate probit models estimated the effects of patient characteristics on home health and informal care utilization. RESULTS: A large majority of the patients (80.6%) received informal care with a smaller proportion (18.6%) receiving home health services. Home health services utilization increased from 9.9% at baseline to 34.5% in year 4. Among users, number of days that services were provided in three-month recall increased from 21.9 to 56 days over time. Home health services utilization was significantly associated with function, depressive symptoms, being female, and not living with a spouse. Informal care utilization was significantly associated with cognition, function, comorbidities, and living with a spouse or child. CONCLUSIONS: Home health and informal care utilization relate differently to patient characteristics. Utilization of home health care or informal care was not influenced by utilization of the other

Clinical Features Associated with Costs in Early AD: Baseline Data from the Predictors Study

BACKGROUND: Few studies on cost of caring for patients with Alzheimer disease (AD) have simultaneously considered multiple dimensions of disease costs and detailed clinical characteristics. OBJECTIVE: To estimate empirically the incremental effects of patients' clinical characteristics on disease costs. METHODS: Data are derived from the baseline visit of 180 patients in the Predictors Study, a large, multicenter cohort of patients with probable AD followed from early stages of the disease. All patients initially lived at home, in retirement homes, or in assisted living facilities. Costs of direct medical care included hospitalizations, outpatient treatment and procedures, assistive devices, and medications. Costs of direct nonmedical care included home health aides, respite care, and adult day care. Indirect costs were measured by caregiving time. Patients' clinical characteristics included cognitive status, functional capacity, psychotic symptoms, behavioral problems, depressive symptoms, extrapyramidal signs, comorbidities, and duration of illness. RESULTS: A 1-point increase in the Blessed Dementia Rating Scale score was associated with a $1,411 increase in direct medical costs and a$2,718 increase in unpaid caregiving costs. Direct medical costs also were $3,777 higher among subjects with depressive symptoms than among those who were not depressed. CONCLUSIONS: Medical care costs and unpaid caregiving costs relate differently to patients' clinical characteristics. Poorer functional status is associated with higher medical care costs and unpaid caregiving costs. Interventions may be particularly useful if targeted in the areas of basic and instrumental activities of daily living

Longitudinal Study of Effects of Patient Characteristics on Direct Costs in Alzheimer Disease

OBJECTIVES: To estimate long-term trajectories of direct cost of caring for patients with Alzheimer disease (AD) and examine the effects of patients' characteristics on cost longitudinally. METHODS: The sample is drawn from the Predictors Study, a large, multicenter cohort of patients with probable AD, prospectively followed up annually for up to 7 years in three university-based AD centers in the United States. Random effects models estimated the effects of patients' clinical and sociodemographic characteristics on direct cost of care. Direct cost included cost associated with medical and nonmedical care. Clinical characteristics included cognitive status (measured by Mini-Mental State Examination), functional capacity (measured by Blessed Dementia Rating Scale [BDRS]), psychotic symptoms, behavioral problems, depressive symptoms, extrapyramidal signs, and comorbidities. The model also controlled for patients' sex, age, and living arrangements. RESULTS: Total direct cost increased from approximately 9,239 dollars per patient per year at baseline, when all patients were at the early stages of the disease, to 19,925 dollars by year 4. After controlling for other variables, a one-point increase in the BDRS score increased total direct cost by 7.7%. One more comorbid condition increased total direct cost by 14.3%. Total direct cost was 20.8% lower for patients living at home compared with those living in an institutional setting. CONCLUSIONS: Total direct cost of caring for patients with Alzheimer disease increased substantially over time. Much of the cost increases were explained by patients' clinical and demographic variables. Comorbidities and functional capacity were associated with higher direct cost over time

Distinct Pools of β-Amyloid in Alzheimer Disease-Affected Brain: A Clinicopathologic Study

Objective: To determine whether β-amyloid (Aβ) peptides segregated into distinct biochemical compartments would differentially correlate with clinical severity of Alzheimer disease (AD). Design: Clinicopathologic correlation study. Participants: Twenty-seven patients from a longitudinal study of AD and 13 age- and sex-matched controls without a known history of cognitive impairment or dementia were included in this study. Interventions: Temporal and cingulate neocortex were processed using a 4-step extraction, yielding biochemical fractions that are hypothesized to be enriched with proteins from distinct anatomical compartments: TRIS (extracellular soluble), Triton (intracellular soluble), sodium dodecyl sulfate (SDS) (membrane associated), and formic acid (extracellular insoluble). Levels of Aβ₄₀ and Aβ₄₂ were quantified in each biochemical compartment by enzyme-linked immunosorbent assay. Results: The Aβ₄₂ level in all biochemical compartments was significantly elevated in patients with AD vs controls (P < .01). The Aβ₄₀ levels in the TRIS and formic acid fractions were elevated in patients with AD (temporal, P < .01; cingulate, P = .03); however, Triton and SDS Aβ₄₀ levels were similar in patients with AD and in controls. Functional impairment proximal to death correlated with Triton Aβ₄₂ (r = 0.48, P = .02) and SDS Aβ₄₂ (r = 0.41, P = .04) in the temporal cortex. Faster cognitive decline was associated with elevated temporal SDS Aβ₄₂ levels (P < .001), whereas slower decline was associated with elevated cingulate formic acid Aβ₄₂ and SDS Aβ₄₂ levels (P = .02 and P = .01, respectively). Conclusion: Intracellular and membrane-associated Aβ, especially Aβ₄₂ in the temporal neocortex, may be more closely related to AD symptoms than other measured Aβ species