Toward a better understanding of nonoccupational sound exposures and associated health impacts: Methods of the Apple Hearing Study.

Globally, noise exposure from occupational and nonoccupational sources is common, and, as a result, noise-induced hearing loss affects tens of millions of people. Occupational noise exposures have been studied and regulated for decades, but nonoccupational sound exposures are not well understood. The nationwide Apple Hearing Study, launched using the Apple research app in November 2019 (Apple Inc., Cupertino, CA), is characterizing the levels at which participants listen to headphone audio content, as well as their listening habits. This paper describes the methods of the study, which collects data from several types of hearing tests and uses the Apple Watch noise app to measure environmental sound levels and cardiovascular metrics. Participants, all of whom have consented to participate and share their data, have already contributed nearly 300 × 106 h of sound measurements and 200 000 hearing assessments. The preliminary results indicate that environmental sound levels have been higher, on average, than headphone audio, about 10% of the participants have a diagnosed hearing loss, and nearly 20% of the participants have hearing difficulty. The study's analyses will promote understanding of the overall exposures to sound and associated impacts on hearing and cardiovascular health. This study also demonstrates the feasibility of collecting clinically relevant exposure and health data outside of traditional research settings.

Bayesian monotonic errors-in-variables models with applications to pathogen susceptibility testing.

Drug dilution (MIC) and disk diffusion (DIA) are the 2 most common antimicrobial susceptibility assays used by hospitals and clinics to determine an unknown pathogen's susceptibility to various antibiotics. Since only one assay is commonly used, it is important that the 2 assays give similar results. Calibration of the DIA assay to the MIC assay is typically done using the error-rate bounded method, which selects DIA breakpoints that minimize the observed discrepancies between the 2 assays. In 2000, Craig proposed a model-based approach that specifically models the measurement error and rounding processes of each assay, the underlying pathogen distribution, and the true monotonic relationship between the 2 assays. The 2 assays are then calibrated by focusing on matching the probabilities of correct classification (susceptible, indeterminant, and resistant). This approach results in greater precision and accuracy for estimating DIA breakpoints. In this paper, we expand the flexibility of the model-based method by introducing a Bayesian 4-parameter logistic model (extending Craig's original 3-parameter model) as well as a Bayesian nonparametric spline model to describe the relationship between the 2 assays. We propose 2 ways to handle spline knot selection, considering many equally spaced knots but restricting overfitting via a random walk prior and treating the number and location of knots as additional unknown parameters. We demonstrate the 2 approaches via a series of simulation studies and apply the methods to 2 real data sets.

Determination of disk diffusion susceptibility testing interpretive criteria using model-based analysis: development and implementation.

The determination of diffusion test breakpoints has become a challenging issue due to the increasing resistance of microorganisms to antibiotics. Currently, the most commonly-used method for determining these breakpoints is the modified error-rate bounded method. Its use has remained widespread despite the introduction of several model-based methods that have been shown superior in terms of precision and accuracy. However, the computational complexities associated with these new approaches has been a significant barrier for clinicians. To remedy this, we developed and examine the utility of a free online software package designed for the determination of diffusion test breakpoints: dBETS (diffusion Breakpoint Estimation Testing Software). This software package allows clinicians to easily analyze data from susceptibility experiments through visualization, error-rate bounded, and model-based approaches. We analyze four publicly available data sets from the Clinical and Laboratory Standards Institute using dBETS.

Unmet Need for Help With Activities of Daily Living Disabilities and Emergency Department Admissions Among Older Medicare Recipients.

Purpose of the Study: This study determined whether self-reports of unmet need for help with activities of daily living (ADL) disabilities are prognostic of emergency department (ED) utilization. Design and Methods: This prospective cohort study of 2,194 community-living, ADL-disabled subjects combined 2004 National Long-Term Care Survey responses with linked Medicare data through 2005. A negative binomial count model was computed to assess the association between unmet ADL need and number of subsequent ED admissions while statistically adjusting for predisposing, enabling, and need characteristics associated with ED admissions among older adults. Results: The adjusted annual incidence rate (IR) for ED admissions was 19% higher for unmet versus met need (IR = 1.19; 95% confidence interval [CI] = 1.00-1.40; p = .047). The IR for ED admissions for falls and injuries was higher for those with unmet ADL versus met ADL need (IR = 1.43; 95% CI = 1.10-1.86), and trended toward significance for ED admissions for skin breakdown (IR = 2.02; 95% CI = 0.97-2.88), but was not significant for ED admissions for dehydration (IR = 1.13; 95% CI= 0.79-1.63). Implications: Unmet ADL need is prognostic of ED admissions, especially for falls and injuries. Future research is needed to determine whether resolution of unmet ADL need reduces ED utilization.

Prognostic Significance of Postoperative Subsyndromal Delirium.

BACKGROUND: Whether postoperative subsyndromal delirium (SSD) is a separate syndrome from delirium and has clinical relevance is not well understood. OBJECTIVES: We sought to investigate SSD in older surgical patients and to determine its prognostic significance. METHODS: We performed a prospective cohort study of patients who were 65 years or older and were scheduled for noncardiac surgery. Postoperative delirium was determined using the Confusion Assessment Method. SSD was defined as the presence of at least one of the possible 10 symptoms of delirium, as defined by the Confusion Assessment Method, but not meeting the criteria for delirium. RESULTS: The number of features of SSD on the first postoperative day was associated with the subsequent development of delirium on the next day, after controlling for other risk factors. When compared with a patient with no SSD features, a patient with 1 SSD feature was 1.07 times more likely to have delirium on the next day (95% CI: 0.42-2.53), with 2 features was 3.32 times more likely to have it (95% CI: 1.42-7.57), and with ≥ 2 features was 8.37 times more likely to have it (95% CI: 4.98-14.53). Furthermore, there was a significant relationship between the number of features of SSD and increased length of hospital stay and worsened functional status at 1 month after surgery. CONCLUSIONS: SSD is prevalent in at-risk surgical patients and has prognostic significance. Only a single symptom of SSD was sufficient to cause a significant increase in hospital length of stay and further decline in functional status. These results suggest that monitoring for SSD is indicated in at-risk patients.

The temporal relationship between early postoperative delirium and postoperative cognitive dysfunction in older patients: a prospective cohort study.

BACKGROUND: Postoperative delirium and cognitive dysfunction are frequent phenomena in older patients; however, few studies have examined the temporal relationship between these two conditions in the early postoperative period. Therefore, this study aimed to determine if postoperative delirium and postoperative cognitive dysfunction (POCD) coexist after major noncardiac surgery. METHODS: This was a prospective cohort study of patients who were ≥ 65 yr of age undergoing noncardiac surgery. Patients were evaluated preoperatively and for two days postoperatively for delirium and POCD. Delirium was determined using the Confusion Assessment Method, and POCD was measured by three cognitive tests addressing changes in executive function, memory, attention, and concentration. For each postoperative day, patients' neurologic status was categorized into three mutually exclusive categories: delirium, POCD, or neither condition. RESULTS: Four hundred sixty-one patients aged ≥ 65 yr of age were studied, and 421 patients with complete postoperative cognitive testing were reported. Eighty percent of patients experienced either delirium or POCD on the first day after surgery. Seventy percent of patients who had delirium on the first postoperative day also had delirium on the second postoperative day. Sixty-three percent of patients who had POCD on postoperative day one continued to have POCD on the next day. Sixteen percent of patients with delirium on day one were non-delirious on day two but met criteria for POCD on day two. Conversely, 15% of patients with POCD on day one became delirious on day two. Only 13% of patients did not experience delirium or POCD on either day after surgery. CONCLUSIONS: Eighty percent of surgical patients experienced some form of cognitive dysfunction the day after surgery, and few recovered by the second day after surgery.

Vitamin D status and resistance exercise training independently affect glucose tolerance in older adults.

We assessed the influence of serum 25-hydroxyvitamin D (25[OH]D) and parathyroid hormone (PTH) concentrations on oral glucose tolerance, body composition, and muscle strength in older, nondiabetic adults who performed resistance exercise training (RT) while consuming diets with either 0.9 or 1.2 g protein kg(-1) d(-1). We hypothesized that individuals with insufficient 25(OH)D and/or high PTH would have less improvement in glucose tolerance after 12 weeks of RT compared with individuals with sufficient 25(OH)D and lower PTH. Sixteen men and 19 women (aged 61 ± 8 years; range, 50-80 years; body mass index, 26.3 ± 3.6 kg/m(2)) performed RT 3 times/wk for 12 weeks, with oral glucose tolerance tests done at baseline and postintervention. Protein intake did not influence the responses described below. Plasma glucose area under the curve (P = .02) and 2-hour plasma glucose concentration (P = .03) were higher for vitamin D-insufficient subjects (25[OH]D <50 nmol/L, n = 7) vs vitamin D-sufficient subjects (25[OH]D ≥50 nmol/L, n = 28). These differences remained significant after adjustment for age and body mass index. Resistance exercise training reduced fat mass (mean ± SD, -6% ± 7%; P < .001) and increased lean body mass (2% ± 3%, P < .001) and whole-body muscle strength (32% ± 17%, P < .001) in these weight-stable subjects but did not affect 25(OH)D or PTH concentrations. Oral glucose tolerance improved after RT (-10% ± 16% in glucose area under the curve and -21% ± 40% in 2-hour glucose, P = .001), but baseline 25(OH)D and PTH did not influence these RT-induced changes. These findings indicate that vitamin D status and RT independently affect glucose tolerance, and a training-induced improvement in glucose tolerance does not offset the negative effect of insufficient vitamin D status in older, nondiabetic adults.

Association between intraoperative blood transfusions and early postoperative delirium in older adults.

OBJECTIVES: To determine whether intraoperative blood transfusion, a known trigger and amplifier of inflammation, is an independent risk factor for early postoperative delirium (POD), an acute state of confusion with fluctuating consciousness and inattention after surgery, in older adults undergoing surgery. DESIGN: Secondary analysis using a database created for a prospective cognitive outcomes study. SETTING: University hospital. PARTICIPANTS: Four hundred seventy-two individuals aged 65 and older undergoing major noncardiac surgery. MEASUREMENTS: Perioperative data were examined for association with POD on the first postoperative day. Multivariable logistic regression analysis was conducted to determine whether intraoperative blood transfusion independently predicts POD after adjusting for covariates known to be associated with onset of delirium and blood transfusions. RESULTS: One hundred thirty-seven individuals (29%) developed delirium on the first postoperative day. The multivariable logistic regression model identified age, sex, history of central nervous system disorder, preoperative cognitive dysfunction, and pain, as well as blood transfusions, as independent risk factors for POD. Intraoperative administration of more than 1,000 mL of red blood cells (RBCs) was the strongest predictor of POD on the first postoperative day (odds ratio = 3.68; 95% confidence interval = 1.32­10.94; P < .001). CONCLUSION: Intraoperative blood transfusion of more than 1,000 mL of RBCs increases the risk of delirium on the first postoperative day in older adults undergoing noncardiac surgery.

Impact of missing data on analysis of postoperative cognitive decline (POCD).

BACKGROUND: There are a variety of techniques to handle missing data, such as removing observations with missing data from the analyses or estimating the missing values using various imputation algorithms. Dropping subjects from standard regression models and analyzing only completers, however, may bias results from the true value of reality. Likewise, 'last-observation-carried-forward' may not be an appropriate technique for studies measuring a particular variable over time. METHODS: This dataset was part of a larger prospective cohort study that examined postoperative cognitive decline (POCD) after surgery in older adults. Data collectors had provided the reasons for data being missing using adjectives including 'confused', 'incapable', 'stuporous', 'comatose', and 'intubated'. Data having these qualitative notations were re-coded as 'incapable' and trial scores of zero were recorded. This value of '0' indicated that the patient was cognitively incapable of performing the neuropsychological test. RESULTS: Missing data varied by cognitive test and postoperative day. Re-coding word list scores from missing to zero when a patient was too cognitively impaired to complete the tests improved sample size by 13.5% of postoperative day (POD) 1 and 12.8% on POD 2. Recoding missing data to zero for the digit symbol test resulted in 29.3% larger sample size on POD 1 and 22.7% on POD 2. Verbal fluency gained 15.7% sample size with re-coding for POD 1 and 13.7% for POD 2. Re-coding of each cognitive test reduced missing data sample size to 20-32% in all cognitive tests for each day. DISCUSSION: Our data suggest that using a scoring system that enters a value of '0' when patients are unable to perform cognitive testing did significantly increase the number of patients that met the diagnosis of postoperative cognitive decline using the criteria that were determined a priori and may lessen chances of type II error (failure to detect a difference).

Hospital readmission among older adults who return home with unmet need for ADL disability.

PURPOSE: This study determined whether returning to the community from a recent hospitalization with unmet activities of daily living (ADL) need was associated with probability of readmission. METHODS: A total of 584 respondents to the 1994, 1999, and/or 2004 National Long-Term Care Surveys (NLTCS) who were hospitalized within 90 days prior to the interview and reported ADL disability at the time of the interview were considered for analysis. Medicare claims linked to the NLTCS provided information about hospital episodes, so those enrolled in Health Maintenance Organizations or Veterans Affairs Medical Centers were not included (n = 62), resulting in a total sample size of 522. ADL disability was defined as needing human help or equipment to complete the task. Unmet ADL need was defined as receiving inadequate or no help for one or more ADL disabilities. Disability that began within 90 days of the interview was considered new disability. RESULTS: After adjusting for demographic, health, and functioning characteristics, unmet ADL need was associated with increased risk for hospital readmission (HR: 1.37, 95% CI: 1.03-1.82). Risk of readmission was greater for those with unmet need for new disabilities than those with unmet need for disabilities that were present before the index hospitalization (HR: 1.66, 95% CI: 1.01-2.73). IMPLICATIONS: Many older patients are discharged from the hospital with ADL disability. Those who report unmet need for new ADL disabilities after they return home from the hospital are particularly vulnerable to readmission. Patients' functional needs after discharge should be carefully evaluated and addressed.

Surface enhanced Raman spectroscopy (SERS) for the discrimination of Arthrobacter strains based on variations in cell surface composition.

Surface enhanced Raman spectroscopy (SERS) is a rapid and highly sensitive spectroscopic technique that has the potential to measure chemical changes in bacterial cell surface in response to environmental changes. The objective of this study was to determine whether SERS had sufficient resolution to differentiate closely related bacteria within a genus grown on solid and liquid medium, and a single Arthrobacter strain grown in multiple chromate concentrations. Fourteen closely related Arthrobacter strains, based on their 16S rRNA gene sequences, were used in this study. After performing principal component analysis in conjunction with Linear Discriminant Analysis, we used a novel, adapted cross-validation method, which more faithfully models the classification of spectra. All fourteen strains could be classified with up to 97% accuracy. The hierarchical trees comparing SERS spectra from the liquid and solid media datasets were different. Additionally, hierarchical trees created from the Raman data were different from those obtained using 16S rRNA gene sequences (a phylogenetic measure). A single bacterial strain grown on solid media culture with three different chromate levels also showed significant spectral distinction at discrete points identified by the new Elastic Net regularized regression method demonstrating the ability of SERS to detect environmentally induced changes in cell surface composition. This study demonstrates that SERS is effective in distinguishing between a large number of very closely related Arthrobacter strains and could be a valuable tool for rapid monitoring and characterization of phenotypic variations in a single population in response to environmental conditions.