Causal diagrams and the logic of matched case-control studies

It is tempting to assume that confounding bias is eliminated by choosing controls that are identical to the cases on the matched confounder(s). We used causal diagrams to explain why such matching not only fails to remove confounding bias, but also adds colliding bias, and why both types of bias are removed by conditioning on the matched confounder(s). As in some publications, we trace the logic of matching to a possible tradeoff between effort and variance, not between effort and bias. Lastly, we explain why the analysis of a matched case-control study – regardless of the method of matching – is not conceptually different from that of an unmatched study

The Straight-Line Depreciation is Wanted, Dead or Alive

We propose a simple axiomatic system that any depreciation method¡ªcomplying with the core of the accounting of depreciation¡ªmust obey. We show that, while none of the prevalent depreciation methods (e.g., straight-line) ex ante conforms to these principles, the accredited proportional depreciation method not only maintains the axiomatic system, but also, for a plausible family of depreciation methods, is the unique method that complies with the axiomatic system. We further propose two consistency requirements of a depreciation method¡ªpartition consistency and dynamic consistency¡ªand show that, in contrast to the commonly used methods, the proportional depreciation method is the only one to always sustain both. Our analysis may provide further resolution to the arguable evidence on the dominance of Funds From Operations over net income in measuring performance in the real estate industry.

Tangible interface for composing music with limited degrees of freedom

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 83-88).This thesis presents SoundStrand, a novel tangible interface for composing music. A new paradigm is also presented - one that allows for music composition with limited degrees of freedom, and therefore is well suited for music creation through the use of tangible interfaces. SoundStrand is comprised of a set of building blocks that represent pre-composed musical segments. By sequentially connecting building blocks to one another, the user arranges these segments into a musical theme; and by individually twisting, stretching and bending the blocks, variations of the melodic, harmonic and rhythmic content are introduced. Software tools are made available to program the musical segments and govern SoundStrand's behavior. Additional work, namely the Coda system, is presented in order to put SoundStrand and the described paradigm in a wider context as tools for music sharing and learning.by Eyal Shahar.S.M

Stroke Mortality, Clinical Presentation and Day of Arrival: The Atherosclerosis Risk in Communities (ARIC) Study

Background. Recent studies report that acute stroke patients who present to the hospital on weekends have higher rates of 28-day mortality than similar patients who arrive during the week. However, how this association is related to clinical presentation and stroke type has not been systematically investigated. Methods and Results. We examined the association between day of arrival and 28-day mortality in 929 validated stroke events in the ARIC cohort from 1987–2004. Weekend arrival was defined as any arrival time from midnight Friday until midnight Sunday. Mortality was defined as all-cause fatal events from the day of arrival through the 28th day of followup. The presence or absence of thirteen stroke signs and symptoms were obtained through medical record review for each event. Binomial logistic regression was used to estimate odds ratios and 95% confidence intervals (OR; 95% CI) for the association between weekend arrival and 28-day mortality for all stroke events and for stroke subtypes. The overall risk of 28-day mortality was 9.6% for weekday strokes and 10.1% for weekend strokes. In models controlling for patient demographics, clinical risk factors, and event year, weekend arrival was not associated with 28-day mortality (0.87; 0.51, 1.50). When stratified by stroke type, weekend arrival was not associated with increased odds of mortality for ischemic (1.17, 0.62, 2.23) or hemorrhagic (0.37; 0.11, 1.26) stroke patients. Conclusions. Presence or absence of thirteen signs and symptoms was similar for weekday patients and weekend patients when stratified by stroke type. Weekend arrival was not associated with 28-day all-cause mortality or differences in symptom presentation for strokes in this cohort

Systematic identification of edited microRNAs in the human brain

Adenosine-to-inosine (A-to-I) editing modifies RNA transcripts from their genomic blueprint. A prerequisite for this process is a double-stranded RNA (dsRNA) structure. Such dsRNAs are formed as part of the microRNA (miRNA) maturation process, and it is therefore expected that miRNAs are affected by A-to-I editing. Editing of miRNAs has the potential to add another layer of complexity to gene regulation pathways, especially if editing occurs within the miRNA–mRNA recognition site. Thus, it is of interest to study the extent of this phenomenon. Current reports in the literature disagree on its extent; while some reports claim that it may be widespread, others deem the reported events as rare. Utilizing a next-generation sequencing (NGS) approach supplemented by an extensive bioinformatic analysis, we were able to systematically identify A-to-I editing events in mature miRNAs derived from human brain tissues. Our algorithm successfully identified many of the known editing sites in mature miRNAs and revealed 17 novel human sites, 12 of which are in the recognition sites of the miRNAs. We confirmed most of the editing events using in vitro ADAR overexpression assays. The editing efficiency of most sites identified is very low. Similar results are obtained for publicly available data sets of mouse brain-regions tissues. Thus, we find that A-to-I editing does alter several miRNAs, but it is not widespread

Validity of hospital discharge diagnosis codes for stroke: The atherosclerosis risk in communities study

BACKGROUND AND PURPOSE: Characterizing International Classification of Disease 9th Revision, Clinical Modification (ICD-9-CM) code validity is essential given widespread use of hospital discharge databases in research. Using the Atherosclerosis Risk in Communities (ARIC) Study, we estimated the accuracy of ICD-9-CM stroke codes. METHODS: Hospitalizations with ICD-9-CM codes 430 to 438 or stroke keywords in the discharge summary were abstracted for ARIC cohort members (1987-2010). A computer algorithm and physician reviewer classified definite and probable ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Using ARIC classification as a gold standard, we calculated the positive predictive value (PPV) and sensitivity of ICD-9-CM codes grouped according to the American Heart Association/American Stroke Association (AHA/ASA) 2013 categories and an alternative code grouping for comparison. RESULTS: Thirty-three percent of 4260 hospitalizations were validated as strokes (1251 ischemic, 120 intracerebral hemorrhage, 46 subarachnoid hemorrhage). The AHA/ASA code groups had PPV 76% and 68% sensitivity compared with PPV 72% and 83% sensitivity for the alternative code groups. The PPV of the AHA/ASA code group for ischemic stroke was slightly higher among blacks, individuals <65 years, and at teaching hospitals. Sensitivity was higher among older individuals and increased over time. The PPV of the AHA/ASA code group for intracerebral hemorrhage was higher among blacks, women, and younger individuals. PPV and sensitivity varied across study sites. CONCLUSIONS: A new AHA/ASA discharge code grouping to identify stroke had similar PPV and lower sensitivity compared with an alternative code grouping. Accuracy varied by patient characteristics and study sites

Association between physical activity and risk of stroke subtypes: The Atherosclerosis Risk in Communities (ARIC) Study

The relationship between stroke subtypes and physical activity is unclear

Obstructive Sleep Apnea and 15-Year Cognitive Decline: The Atherosclerosis Risk in Communities (ARIC) Study

Prospective data evaluating abnormal sleep quality and quantity with cognitive decline are limited because most studies used subjective data and/or had short follow-up. We hypothesized that, over 15 y of follow-up, participants with objectively measured obstructive sleep apnea (OSA) and other indices of poor sleep quantity and quality would experience greater decline in cognitive functioning than participants with normal sleep patterns