Charline Maertens de Noordhout

Disability weights for the Global Burden of Disease 2013 study

BACKGROUND The Global Burden of Disease (GBD) study assesses health losses from diseases, injuries, and risk factors using disability-adjusted life-years, which need a set of disability weights to quantify health levels associated with non-fatal outcomes. The objective of this study was to estimate disability weights for the GBD 2013 study. METHODS We analysed data from new web-based surveys of participants aged 18-65 years, completed in four European countries (Hungary, Italy, the Netherlands, and Sweden) between Sept 23, 2013, and Nov 11, 2013, combined with data previously collected in the GBD 2010 disability weights measurement study. Surveys used paired comparison questions for which respondents considered two hypothetical individuals with different health states and specified which person they deemed healthier than the other. These surveys covered 183 health states pertinent to GBD 2013; of these states, 30 were presented with descriptions revised from previous versions and 18 were new to GBD 2013. We analysed paired comparison data using probit regression analysis and rescaled results to disability weight units between 0 (no loss of health) and 1 (loss equivalent to death). We compared results with previous estimates, and an additional analysis examined sensitivity of paired comparison responses to duration of hypothetical health states. FINDINGS The total analysis sample consisted of 30 230 respondents from the GBD 2010 surveys and 30 660 from the new European surveys. For health states common to GBD 2010 and GBD 2013, results were highly correlated overall (Pearsons r 0·992 [95% uncertainty interval 0·989-0·994]). For health state descriptions that were revised for this study, resulting disability weights were substantially different for a subset of these weights, including those related to hearing loss (eg, complete hearing loss: GBD 2010 0·033 [0·020-0·052]; GBD 2013 0·215 [0·144-0·307]) and treated spinal cord lesions (below the neck: GBD 2010 0·047 [0·028-0·072]; GBD 2013 0·296 [0·198-0·414]; neck level: GBD 2010 0·369 [0·243-0·513]; GBD 2013 0·589 [0·415-0·748]). Survey responses to paired comparison questions were insensitive to whether the comparisons were framed in terms of temporary or chronic outcomes (Pearsons r 0·981 [0·973-0·987]). INTERPRETATION This study substantially expands the empirical basis for assessment of non-fatal outcomes in the GBD study. Findings from this study substantiate the notion that disability weights are sensitive to particular details in descriptions of health states, but robust to duration of outcomes. FUNDING European Centre for Disease Prevention and Control, Bill and Melinda Gates Foundation.

The global burden of listeriosis: a systematic review and meta-analysis

BACKGROUND Listeriosis, caused by Listeria monocytogenes, is an important foodborne disease that can be difficult to control and commonly results in severe clinical outcomes. We aimed to provide the first estimates of global numbers of illnesses, deaths, and disability-adjusted life-years (DALYs) due to listeriosis, by synthesising information and knowledge through a systematic review. METHODS We retrieved data on listeriosis through a systematic review of peer-reviewed and grey literature (published in 1990-2012). We excluded incidence data from before 1990 from the analysis. We reviewed national surveillance data where available. We did a multilevel meta-analysis to impute missing country-specific listeriosis incidence rates. We used a meta-regression to calculate the proportions of health states, and a Monte Carlo simulation to generate DALYs by WHO subregion. FINDINGS We screened 11,722 references and identified 87 eligible studies containing listeriosis data for inclusion in the meta-analyses. We estimated that, in 2010, listeriosis resulted in 23,150 illnesses (95% credible interval 6061-91,247), 5463 deaths (1401-21,497), and 172,823 DALYs (44,079-676,465). The proportion of perinatal cases was 20·7% (SD 1·7). INTERPRETATION Our quantification of the global burden of listeriosis will enable international prioritisation exercises. The number of DALYs due to listeriosis was lower than those due to congenital toxoplasmosis but accords with those due to echinococcosis. Urgent efforts are needed to fill the missing data in developing countries. We were unable to identify incidence data for the AFRO, EMRO, and SEARO WHO regions. FUNDING WHO Foodborne Diseases Epidemiology Reference Group and the Université catholique de Louvain.

Calculating disability-adjusted life years to quantify burden of disease

The disability-adjusted life year or DALY is a summary measure of public health widely used to quantify burden of disease. In the DALY philosophy, every person is born with a certain number of life years potentially lived in optimal health. People may lose these healthy life years through living with illness and/or through dying before a reference life expectancy. These losses in healthy life years are exactly what is measured by the DALY metric. Ten DALYs, for instance, correspond to ten lost years of healthy life, attributable to morbidity, mortality, or both. On a population level, diseases with a higher public health impact will thus account for more DALYs than those with a lesser impact. DALYs have been the key measure in the four Global Burden of Disease (GBD) studies, each presenting a comprehensive assessment of the worldwide health impact of disease, injury and risk factors (Murray and Lopez 1996; Lopez et al. 2006; World Health Organization 2008; Murray et al. 2013a; Lopez 2013). Table 1 shows the most important diseases according to the different GBD studies. Furthermore, various national and regional DALY calculations have been performed to assess and monitor local health and to set priorities within the local health sector (e.g., Melse et al. 2000; Mathers et al. 2001; Devleesschauwer et al. 2013; Shield et al. 2013). In this Hints and Kinks paper, we summarize the DALY’s basic features and present a description of its calculation. An ‘‘Appendix’’ includes R code to calculate DALYs. The

DALY calculation in practice: a stepwise approach

disability weight ð1Þ YLL 1⁄4 Number of deaths life expectancy at the age of death ð2Þ DALY 1⁄4 YLD þ YLL ð3Þ The philosophical and methodological aspects of the DALY calculation have been described (and debated) in great detail (Murray 1994; Murray and Acharya 1997; for critiques, see, amongst others, Anand and Hanson 1997), and are summarized in the accompanying Hints and Kinks paper (Devleesschauwer et al. 2014). The steps preceding the actual calculation, however, remain less well documented. This Hints and Kinks paper tries to address this gap by presenting a stepwise approach towards a DALY calculation.

The burden of parasitic zoonoses in Nepal: a systematic review

Background Parasitic zoonoses (PZs) pose a significant but often neglected threat to public health, especially in developing countries. In order to obtain a better understanding of their health impact, summary measures of population health may be calculated, such as the Disability-Adjusted Life Year (DALY). However, the data required to calculate such measures are often not readily available for these diseases, which may lead to a vicious circle of under-recognition and under-funding. Methodology We examined the burden of PZs in Nepal through a systematic review of online and offline data sources. PZs were classified qualitatively according to endemicity, and where possible a quantitative burden assessment was conducted in terms of the annual number of incident cases, deaths and DALYs. Principal Findings Between 2000 and 2012, the highest annual burden was imposed by neurocysticercosis and congenital toxoplasmosis (14,268 DALYs [95% Credibility Interval (CrI): 5450–27,694] and 9255 DALYs [95% CrI: 6135–13,292], respectively), followed by cystic echinococcosis (251 DALYs [95% CrI: 105–458]). Nepal is probably endemic for trichinellosis, toxocarosis, diphyllobothriosis, foodborne trematodosis, taeniosis, and zoonotic intestinal helminthic and protozoal infections, but insufficient data were available to quantify their health impact. Sporadic cases of alveolar echinococcosis, angiostrongylosis, capillariosis, dirofilariosis, gnathostomosis, sparganosis and cutaneous leishmaniosis may occur. Conclusions/Significance In settings with limited surveillance capacity, it is possible to quantify the health impact of PZs and other neglected diseases, thereby interrupting the vicious circle of neglect. In Nepal, we found that several PZs are endemic and are imposing a significant burden to public health, higher than that of malaria, and comparable to that of HIV/AIDS. However, several critical data gaps remain. Enhanced surveillance for the endemic PZs identified in this study would enable additional burden estimates, and a more complete picture of the impact of these diseases.

Assessing disability weights based on the responses of 30,660 people from four European countries

BackgroundIn calculations of burden of disease using disability-adjusted life years, disability weights are needed to quantify health losses relating to non-fatal outcomes, expressed as years lived with disability. In 2012 a new set of global disability weights was published for the Global Burden of Disease 2010 (GBD 2010) study. That study suggested that comparative assessments of different health outcomes are broadly similar across settings, but the significance of this conclusion has been debated. The aim of the present study was to estimate disability weights for Europe for a set of 255 health states, including 43 new health states, by replicating the GBD 2010 Disability Weights Measurement study among representative population samples from four European countries.MethodsFor the assessment of disability weights for Europe we applied the GBD 2010 disability weights measurement approach in web-based sample surveys in Hungary, Italy, Netherlands, and Sweden. The survey included paired comparisons (PC) and population health equivalence questions (PHE) formulated as discrete choices. Probit regression analysis was used to estimate cardinal values from PC responses. To locate results onto the 0-to-1 disability weight scale, we assessed the feasibility of using the GBD 2010 scaling approach based on PHE questions, as well as an alternative approach using non-parametric regression.ResultsIn total, 30,660 respondents participated in the survey. Comparison of the probit regression results from the PC responses for each country indicated high linear correlations between countries. The PHE data had high levels of measurement error in these general population samples, which compromises the ability to infer ratio-scaled values from discrete choice responses. Using the non-parametric regression approach as an alternative rescaling procedure, the set of disability weights were bounded by distance vision mild impairment and anemia with the lowest weight (0.004) and severe multiple sclerosis with the highest weight (0.677).ConclusionsPC assessments of health outcomes in this study resulted in estimates that were highly correlated across four European countries. Assessment of the feasibility of rescaling based on a discrete choice formulation of the PHE question indicated that this approach may not be suitable for use in a web-based survey of the general population.

Quantifying burden of disease to support public health policy in Belgium: opportunities and constraints

BackgroundTo support public health policy, information on the burden of disease is essential. In recent years, the Disability-Adjusted Life Year (DALY) has emerged as the most important summary measure of public health. DALYs quantify the number of healthy life years lost due to morbidity and mortality, and thereby facilitate the comparison of the relative impact of diseases and risk factors and the monitoring of public health over time.DiscussionEvidence on the disease burden in Belgium, expressed as DALYs, is available from international and national efforts. Non-communicable diseases and injuries dominate the overall disease burden, while dietary risks, tobacco smoking, and high body-mass index are the major risk factors for ill health. Notwithstanding these efforts, if DALYs were to be used for guiding health policy, a more systematic approach is required. By integrating DALYs in the current data generating systems, comparable estimates, rooted in recent local data, can be produced. This might however be hampered by several restrictions, such as limited harmonization, timeliness, inclusiveness and accessibility of current databases.SummaryRoutine quantification of disease burden in terms of DALYs would provide a significant added value to evidence-based public health policy in Belgium, although some hurdles need to be cleared.

Current and future Disability-Adjusted Life Years (DALYs) of Salmonella and Campylobacter in Belgium

Salmonellosis and campylobacteriosis are major foodborne diseases caused by consumption of contaminated raw pork or poultry. Symptomatic disease is mainly characterized by gastroenteritis, although immunoreactive complications also occur, especially among the immunocompromised. Although these diseases cause the highest number of confirmed foodborne bacterial infections in Belgium, their real and future population health impact remains unknown. The objectives of this study were to estimate and forecast the number of Salmonella and Campylobacter cases in Belgium from 2012 to 2020 and to calculate the corresponding number of Disability-Adjusted Life Years. The time series of laboratory-confirmed Salmonella cases ranged from 2001 to 2012, and that of Campylobacter cases from 1993 to 2013. We developed a Bai and Perron two breakpoint model to design salmonellosis time series taking into account the multiple changes in Salmonella spp. transmission and control. We developed a dynamic linear model for campylobacteriosis because the data showed a stochastic drift, varied locally and suffered from parameter stability issues around the seasonal component of the data. We calculated DALYs using standard formulas. The salmonellosis forecast showed a continued decline after 2005. The average monthly number of salmonellosis cases was 264 in 2012 and predicted to be 212 in 2020 (Standard Deviation [SD] 87). Salmonellosis caused 173 DALYs (95% Uncertainty Interval [UI] 33-433) per 100,000 in 2012 and 177 DALYs (95% UI 32-430) per 100,000 in 2020. The average monthly number of campylobacteriosis cases was 633 in 2012, with the predictions showing an upward trend until 2020 to an average of 1081 (SD 311) cases per month. Campylobacteriosis caused 25 DALYs (95% UI 9-60) per 100,000 in 2012 and 40 DALYs (95% UI 14-101) per 100,000 in 2020. Assuming a constant environment, the burden of salmonellosis will stay stable and the burden of campylobacteriosis may almost double until 2020.

National studies as a component of the World Health Organization initiative to estimate the global and regional burden of foodborne disease

Background The World Health Organization (WHO) initiative to estimate the global burden of foodborne diseases established the Foodborne Diseases Burden Epidemiology Reference Group (FERG) in 2007. In addition to global and regional estimates, the initiative sought to promote actions at a national level. This involved capacity building through national foodborne disease burden studies, and encouragement of the use of burden information in setting evidence-informed policies. To address these objectives a FERG Country Studies Task Force was established and has developed a suite of tools and resources to facilitate national burden of foodborne disease studies. This paper describes the process and lessons learned during the conduct of pilot country studies under the WHO FERG initiative. Findings Pilot country studies were initiated in Albania, Japan and Thailand in 2011 and in Uganda in 2012. A brief description of each study is provided. The major scientific issue is a lack of data, particularly in relation to disease etiology, and attribution of disease burden to foodborne transmission. Situation analysis, knowledge translation, and risk communication to achieve evidence-informed policies require specialist expertise and resources. Conclusions The FERG global and regional burden estimates will greatly enhance the ability of individual countries to fill data gaps and generate national estimates to support efforts to reduce the burden of foodborne disease.

Welfare-Adjusted Life Years (WALY): A novel metric of animal welfare that combines the impacts of impaired welfare and abbreviated lifespan

Currently, separate measures are used to estimate the impact of animal diseases on mortality and animal welfare. This article introduces a novel metric, the Welfare-Adjusted Life Year (WALY), to estimate disease impact by combining welfare compromise and premature death components. Adapting the Disability-Adjusted Life Year approach used in human health audits, we propose WALY as the sum of a) the years lived with impaired welfare due to a particular cause and b) the years of life lost due to the premature death from the same cause. The years lived with impaired welfare are the product of the average duration of each welfare impediment, reflecting the actual condition that compromises animal welfare, the probability of an incident case developing and impaired welfare weights, representing the degree of impaired welfare. The years of life lost are calculated using the standard expected lifespan at the time of premature death. To demonstrate the concept, we estimated WALYs for 10 common canine diseases, namely mitral valve disease, dilated cardiomyopathy, chronic kidney disease, diabetes mellitus, atopic dermatitis, splenic haemangiosarcoma, appendicular osteosarcoma, cranial cruciate ligament disease, thoracolumbar intervertebral disc disease and cervical spondylomyelopathy. A survey of veterinarians (n = 61) was conducted to elicit impaired welfare weights for 35 welfare impediments. Paired comparison was the primary method to elicit weights, whereas visual analogue scale and time trade-off approaches rescaled these weights onto the desired scale, from 0 (the optimal welfare imaginable) to 1 (the worst welfare imaginable). WALYs for the 10 diseases were then estimated using the impaired welfare weights and published epidemiological data on disease impacts. Welfare impediment “amputation: one limb” and “respiratory distress” had the lowest and highest impaired welfare weights at 0.134 and 0.796, rescaled with a visual analogue scale, and 0.117 and 0.857, rescaled with time trade-off. Among the 10 diseases, thoracolumbar intervertebral disc disease and atopic dermatitis had the smallest and greatest adverse impact on dogs with WALYs at 2.83 (95% UI: 1.54–3.94) and 9.73 (95% uncertainty interval [UI]: 7.17–11.8), respectively. This study developed the WALY metric and demonstrated that it summarises welfare compromise as perceived by humans and total impact of diseases in individual animals. The WALY can potentially be used for prioritisation of disease eradication and control programs, quantification of population welfare and longitudinal surveillance of animal welfare in companion animals and may possibly be extended to production animals.