Marine vessel wave wake: transient effects when accelerating or decelerating

It is well known that the waves generated by marine vessels, often referred to as wave wake or wash, can cause many issues when operating in sheltered waterways, including, but not limited to, erosion of shorelines and damage to maritime structures, and present a danger to other waterway users. Much research has been undertaken to understand the characteristics of these waves and their effects better, especially for high-speed vessels that operate in shallow water where particularly large and energetic waves are generated. However, in general, all previous studies have considered only steady-state conditions in which vessel speed remains constant; however, many vessel operations, particularly those of commuter ferries, in which regular passages through the transcritical zone to supercritical speeds (in terms of depth Froude number) are required. The present study describes a novel series of model-scale experiments used to quantify the waves during both acceleration and deceleration phases. Notable transient effects were found to occur during the acceleration phase that significantly increased both the height and period of the maximum wave compared to height and period of the maximum wave occurring at the corresponding steady-state speed. The wave characteristics at constant speed were used when assessing whether a particular vessel met wash criteria, and such criteria were likely significantly exceeded when a vessel accelerated to a supercritical speed, which could lead to the occurrence of wave wake issues. In an interesting finding, the study also found no such increase in wave characteristics when the same vessel decelerated back through the transcritical speed zone

A meta-analysis of health state valuations for people with diabetes: Explaining the variation across methods and implications for economic evaluation

To review published studies on the effect of diabetes and its complications on utility scores to establish whether there is systematic variation across studies and to examine the implications for the estimation of quality-adjusted life years (QALYs). A systematic review was performed using studies reporting QALY measures elicited from people with diabetes including those with a history of complications. Meta-analysis was used to obtain the average utility, and meta-regression was employed to examine the impact of study characteristics and elicitation methods on these values. The effect of different utility scores on QALYs was examined using diabetes simulation models. In the meta-analysis based on 45 studies reporting 66 values, the average utility score was 0.76 (95% CI 0.75-0.77). A meta-regression showed significant variation due to age, method of elicitation and the proportion of males. The average utility score for individual complications ranged from 0.48 (95% CI 0.25, 0.71) for chronic renal disease to 0.75 (95% CI 0.73, 0.78) for myocardial infarction, and these differences produced meaningful changes in simulated QALYs. There was significant heterogeneity between studies. We provide summary utility scores for diabetes and its major complications that could help inform economic evaluation and policy analysis. © 2011 Springer Science+Business Media B.V

Recent trends in life expectancy for people with type 1 diabetes in Sweden

AIMS/HYPOTHESIS: People with type 1 diabetes have reduced life expectancy (LE) compared with the general population. Our aim is to quantify mortality changes from 2002 to 2011 in people with type 1 diabetes in Sweden. METHODS: This study uses health records from the Swedish National Diabetes Register (NDR) linked with death records. Abridged period life tables for those with type 1 diabetes aged 20 years and older were derived for 2002-06 and 2007-11 using Chiang's method. Cox proportional hazard models were used to assess trends in overall and cause-specific mortality. RESULTS: There were 27,841 persons aged 20 years and older identified in the NDR as living with type 1 diabetes between 2002 and 2011, contributing 194,685 person-years of follow-up and 2,018 deaths. For men with type 1 diabetes, the remaining LE at age 20 increased significantly from 47.7 (95% CI 46.6, 48.9) in 2002-06 to 49.7 years (95% CI 48.9, 50.6) in 2007-11. For women with type 1 diabetes there was no significant change, with an LE at age 20 of 51.7 years (95% CI 50.3, 53.2) in 2002-06 and 51.9 years (95% CI 50.9, 52.9) in 2007-11. Cardiovascular mortality significantly reduced, with a per year HR of 0.947 (95% CI 0.917, 0.978) for men and 0.952 (95% CI 0.916, 0.989) for women. CONCLUSIONS/INTERPRETATION: From 2002-06 to 2007-11 the LE at age 20 of Swedes with type 1 diabetes increased by approximately 2 years for men but minimally for women. These recent gains have been driven by reduced cardiovascular mortality

Severe Hypoglycemia and Mortality After Cardiovascular Events for Type 1 Diabetic Patients in Sweden

OBJECTIVE: To examine whether previous severe hypoglycemic events were associated with the risk of all-cause mortality after major cardiovascular events (myocardial infarction [MI] or stroke) in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS: This study is based on data from the Swedish National Diabetes Register linked to patient-level hospital records, prescription data, and death records. We selected patients with type 1 diabetes who visited a clinic during 2002-2010 and experienced a major cardiovascular complication after their clinic visit. We estimated a two-part model for all-cause mortality after a major cardiovascular event: logistic regression for death within the first month and a Cox proportional hazards model conditional on 1-month survival. At age 60 years, 5-year cumulative mortality risk was estimated from the models for patients with and without prior diabetes complications. RESULTS: A total of 1,839 patients experienced major cardiovascular events, of whom 403 had previously experienced severe hypoglycemic events and 703 died within our study period. A prior hypoglycemic event was associated with a significant increase in mortality after a cardiovascular event, with hazard ratios estimated at 1.79 (95% CI 1.37-2.35) within the first month and 1.25 (95% CI 1.02-1.53) after 1 month. Patients with prior hypoglycemia had an estimated 5-year cumulative mortality risk of 52.4% (95% CI 45.3-59.5) and 39.8% (95% CI 33.4-46.3) for MI and stroke, respectively. CONCLUSIONS: We have found evidence that patients with type 1 diabetes in Sweden with prior severe hypoglycemic events have increased risk of mortality after a cardiovascular event

Self‐rated health scores predict mortality among people with type 2 diabetes differently across three different country groupings: findings from the ADVANCE and ADVANCE‐ON trials

Aims To explore whether there is a different strength of association between self‐rated health and all‐cause mortality in people with type 2 diabetes across three country groupings: nine countries grouped together as 'established market economies'; Asia; and Eastern Europe. Methods The ADVANCE trial and its post‐trial follow‐up were used in this study, which included 11 140 people with type 2 diabetes from 20 countries, with a median follow‐up of 9.9 years. Self‐rated health was reported on a 0–100 visual analogue scale. Cox proportional hazard models were fitted to estimate the relationship between the visual analogue scale score and all‐cause mortality, controlling for a range of demographic and clinical risk factors. Interaction terms were used to assess whether the association between the visual analogue scale score and mortality varied across country groupings. Results The visual analogue scale score had different strengths of association with mortality in the three country groupings. A 10‐point increase in visual analogue scale score was associated with a 15% (95% CI 12–18) lower mortality hazard in the established market economies, a 25% (95% CI 21–28) lower hazard in Asia, and an 8% (95% CI 3–13) lower hazard in Eastern Europe. Conclusions Self‐rated health appears to predict 10‐year all‐cause mortality for people with type 2 diabetes worldwide, but this relationship varies across groups of countries.</p

Self-rated health scores predict mortality among people with type 2 diabetes differently across three different country groupings: findings from the ADVANCE and ADVANCE-ON trials

Aims To explore whether there is a different strength of association between self‐rated health and all‐cause mortality in people with type 2 diabetes across three country groupings: nine countries grouped together as 'established market economies'; Asia; and Eastern Europe. Methods The ADVANCE trial and its post‐trial follow‐up were used in this study, which included 11 140 people with type 2 diabetes from 20 countries, with a median follow‐up of 9.9 years. Self‐rated health was reported on a 0–100 visual analogue scale. Cox proportional hazard models were fitted to estimate the relationship between the visual analogue scale score and all‐cause mortality, controlling for a range of demographic and clinical risk factors. Interaction terms were used to assess whether the association between the visual analogue scale score and mortality varied across country groupings. Results The visual analogue scale score had different strengths of association with mortality in the three country groupings. A 10‐point increase in visual analogue scale score was associated with a 15% (95% CI 12–18) lower mortality hazard in the established market economies, a 25% (95% CI 21–28) lower hazard in Asia, and an 8% (95% CI 3–13) lower hazard in Eastern Europe. Conclusions Self‐rated health appears to predict 10‐year all‐cause mortality for people with type 2 diabetes worldwide, but this relationship varies across groups of countries