This paper aims to provide a basis for the improvement of software estimation research through a systematic review of previous work. The review identifies 304 software cost estimation papers in 76 journals and classifies the papers according to research topic, estimation approach, research approach, study context and data set. Based on the review, we provide recommendations for future software cost estimation research: 1) Increase the breadth of the search for relevant studies, 2) Search manually for relevant papers within a carefully selected set of journals when completeness is essential, 3) Conduct more research on basic software cost estimation topics, 4) Conduct more studies of software cost estimation in real-life settings, 5) Conduct more studies on estimation methods commonly used by the software industry, and, 6) Conduct fewer studies that evaluate methods based on arbitrarily chosen data sets.

In this study from the general practice sector, a reverse J-shaped relation between the serum level of 25(OH)D and all-cause mortality was observed, indicating not only a lower limit but also an upper limit. The lowest mortality risk was at 50-60 nmol/liter. The study did not allow inference of causality, and further studies are needed to elucidate a possible causal relationship between 25(OH)D levels, especially higher levels, and mortality.

Background and purpose Hip fractures are associated with high mortality, but the cause of this is still not entirely clear. We investigated the effect of surgical delay, weekends, holidays, and time of day admission on mortality in hip fracture patients.Patients and methods Using data from the Danish National Indicator Project, we identified 38,020 patients admitted from 2003 to 2010. Logistic regression analysis was used to study the association between sex, age, weekend or holiday admission, night-time admission, time to surgery, and ASA score on the one hand and mortality on the other.Results The risk of death in hospital increased with surgical delay (odds ratio (OR) = 1.3 per 24 h of delay), ASA score (OR (per point added) = 2.3), sex (OR for men 2.2), and age (OR (per 5 years) = 1.4). The mortality rate for patients admitted during weekends or public holidays, or at night, was similar to that found for those admitted during working days.Interpretation Minimizing surgical delay is the most important factor in reducing mortality in hip fracture patients.

In this large observational study, low and high levels of 25(OH)D were associated with cardiovascular disease, stroke, and acute myocardial mortality in a nonlinear, reverse J-shaped manner, with the highest risk at lower levels. Whether this was a causal or associational finding cannot be determined from our data. There is a need for randomized clinical trials that include information on the effects of 25(OH)D levels greater than 100 nmol/L.