Algorithmic statistics: forty years later

Algorithmic statistics has two different (and almost orthogonal) motivations. From the philosophical point of view, it tries to formalize how the statistics works and why some statistical models are better than others. After this notion of a "good model" is introduced, a natural question arises: it is possible that for some piece of data there is no good model? If yes, how often these bad ("non-stochastic") data appear "in real life"? Another, more technical motivation comes from algorithmic information theory. In this theory a notion of complexity of a finite object (=amount of information in this object) is introduced; it assigns to every object some number, called its algorithmic complexity (or Kolmogorov complexity). Algorithmic statistic provides a more fine-grained classification: for each finite object some curve is defined that characterizes its behavior. It turns out that several different definitions give (approximately) the same curve. In this survey we try to provide an exposition of the main results in the field (including full proofs for the most important ones), as well as some historical comments. We assume that the reader is familiar with the main notions of algorithmic information (Kolmogorov complexity) theory.Comment: Missing proofs adde

Aneurysmal and clinical characteristics as risk factors for intracerebral haematoma from aneurysmal rupture

Intracerebral haematoma (ICH) occurs in one-third of patients with aneurysmal subarachnoid haemorrhage (SAH) and is associated with poor prognosis. Identification of risk factors for ICH from aneurysmal rupture may help in balancing risks of treatment of unruptured aneurysms. We assessed potential clinical and aneurysmal risk factors for ICH from aneurysmal rupture. In all 310 SAH patients admitted to our service between 2005 and 2007, we compared clinical risk factors (gender, age, smoking, hypertension, history of SAH and family history) of patients with and without an ICH. From the latest admitted, 50 patients with and 50 without ICH, we compared the location, shape and direction of blood flow of the aneurysms on CT-angiography. Relative risks (RRs) of ICH were 1.2 (95% confidence interval, CI):0.7–1.8) for males, 1.0 (95%CI:0.7–1.4) for age ≥55 year, 1.0 (95%CI:0.6–1.6) for smoking, 0.9 (95%CI:0.5–1.5) for hypertension, 0.6 (95%CI:0.1–3.8) for history of SAH and 0.5 (95%CI:0.2–1.3) for family history of SAH. RRs of ICH were 1.8 (95%CI:1.2–2.5) for MCA aneurysms, 0.5 (95%CI:0.3–1.0) for ICA aneurysms, 0.4 (95%CI:0.1–1.3) for posterior circulation aneurysms, and 0.7 (95%CI:0.3–1.3) for multilobed aneurysms. The RRs of other aneurysmal characteristics varied between 0.9 and 1.2. Patients with MCA aneurysms are at a higher risk of developing ICH. The other aneurysmal or clinical factors have no or only minor influence on the risk of ICH after rupture and are, therefore, not helpful in deciding on treatment of unruptured aneurysms

Effect of weekend admission on in-hospital mortality and functional outcomes for patients with acute subarachnoid haemorrhage (SAH)

BACKGROUND: Aneurysmal subarachnoid haemorrhage (aSAH) is an acute cerebrovascular event with high socioeconomic impact as it tends to affect younger patients. The recent NCEPOD study looking into management of aSAH has recommended that neurovascular units in the United Kingdom should aim to secure cerebral aneurysms within 48 h and that delays because of weekend admissions can increase the mortality and morbidity attributed to aSAH. METHOD: We used data from a prospective audit of aSAH patients admitted between January 2009 and December 2011. The baseline demographic and clinical features of the weekend and weekday groups were compared using the chi-squared test and T-test. Cox proportional hazards models (Proc Phreg in SAS) were used to calculate the adjusted overall hazard of in-hospital death associated with admission on weekend, adjusting for age, sex, baseline WFNS grade, type of treatment received and time from scan to treatment. Sliding dichotomy analysis was used to estimate the difference in outcomes after SAH at 3 months in weekend and weekday admissions. RESULTS: Those admitted on weekends had a significantly higher scan to treatment time (83.05 ± 83.4 h vs 40.4 ± 53.4 h, P < 0.0001) and admission to treatment (71.59 ± 79.8 h vs 27.5 ± 44.3 h, P < 0.0001) time. After adjustments for adjusted for relevant covariates weekend admission was statistically significantly associated with excess in-hospital mortality (HR = 2.1, CL [1.13–4.0], P = 0.01). After adjustments for all the baseline covariates, the sliding dichotomy analysis did not show effects of weekend admission on long-term outcomes on the good, intermediate and worst prognostic bands. CONCLUSIONS: This study provides important data showing excess in-hospital mortality of patients with SAH on weekend admissions served by the United Kingdom’s National Health Service.; However, there were no effects of weekend admission on long-term outcomes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00701-016-2746-z) contains supplementary material, which is available to authorized users

Aneurismal subarachnoid hemorrhage in a Chilean population, with emphasis on risk factors

<p>Abstract</p> <p>Background</p> <p>Subarachnoid Hemorrhage (SAH) is caused principally by the rupture of intracranial aneurisms. Important risk factors have been described such as age, sex, hypertension (HT) and season of the year, among others. The objective is to investigate the demographic characteristics and possible risk factors in a population of Chilean patients.</p> <p>Methods</p> <p>This retrospective study was based on the analysis of 244 clinical records of patients diagnosed with aneurismal SAH who were discharged from the Instituto de Neurocirugía ASENJO in Santiago, Chile.</p> <p>Results</p> <p>The mean age of patients was 49.85 years and the male:female ratio was 1:2.7. The signs and symptoms were not different between sexes; cephalea (85.7%) was predominant, followed by loss of consciousness, vomiting/nausea and meningeal signs. Risk factors included sex, age and HT. Concordant with other reports, the incidence of SAH was greatest in spring.</p> <p>Conclusions</p> <p>The demographic characteristics and risk factors observed in patients with aneurismal SAH treated in ASENJO were comparable to those of other populations. We were not able to conclude that tobacco and alcohol consumption were risk factors for this population.</p

Emergency department clinical leads’ experiences of implementing primary care services where GPs work in or alongside emergency departments in the UK: a qualitative study

Background To manage increasing demand for emergency and unscheduled care NHS England policy has promoted services in which patients presenting to Emergency Departments (EDs) with non-urgent problems are directed to general practitioners (GPs) and other primary care clinicians working within or alongside emergency departments. However, the ways that hospitals have implemented primary care services in EDs are varied. The aim of this study was to describe ED clinical leads’ experiences of implementing and delivering ‘primary care services’ and ‘emergency medicine services’ where GPs were integrated into the ED team. Methods We conducted interviews with ED clinical leads in England (n = 19) and Wales (n = 2). We used framework analysis to analyse interview transcripts and explore differences across ‘primary care services’, ‘emergency medicine services’ and emergency departments without primary care services. Results In EDs with separate primary care services, success was reported when having a distinct workforce of primary care clinicians, who improved waiting times and flow by seeing primary care-type patients in a timely way, using fewer investigations, and enabling ED doctors to focus on more acutely unwell patients. Some challenges were: trying to align their service with the policy guidance, inconsistent demand for primary care, accessible community primary care services, difficulties in recruiting GPs, lack of funding, difficulties in agreeing governance protocols and establishing effective streaming pathways. Where GPs were integrated into an ED workforce success was reported as managing the demand for both emergency and primary care and reducing admissions. Conclusions Introducing a policy advocating a preferred model of service to address primary care demand was not useful for all emergency departments. To support successful and sustainable primary care services in or alongside EDs, policy makers and commissioners should consider varied ways that GPs can be employed to manage variation in local demand and also local contextual factors such as the ability to recruit and retain GPs, sustainable funding, clear governance frameworks, training, support and guidance for all staff. Whether or not streaming to a separate primary care service is useful also depended on the level of primary care demand