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Disease burden

Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs), both of which quantify the number of years lost due to disease (YLDs). One DALY can be thought of as one year of healthy life lost, and the overall disease burden can be thought of as a measure of the gap between current health status and the ideal health status (where the individual lives to old age free from disease and disability).[1][2][3] According to an article published in The Lancet in June 2015 low back pain and major depressive disorder were among the top ten causes of YLDs and were the cause of more health loss than diabetes, chronic obstructive pulmonary disease, and asthma combined. The study based on data from 188 countries, considered to be the largest and most detailed analysis to quantify levels, patterns, and trends in ill health and disability, concluded that "the proportion of disability-adjusted life years due to YLDs increased globally from 21·1% in 1990 to 31·2% in 2013."[4] The environmental burden of disease is defined as the number of DALYs that can be attributed to environmental factors.[3][5][6] These measures allow for comparison of disease burdens, and have also been used to forecast the possible impacts of health interventions. By 2014 DALYs per head were "40% higher in low-income and middle-income regions."[7]

The

  • Lucas, Robyn. "Solar ultraviolet radiation: Assessing the environmental burden of disease at national and local levels" (PDF). Environmental burden of disease series 17. World Health Organization. 
  • "Metrics: Disability-Adjusted Life Year (DALY)". Health statistics and health information systems. World Health Organization. 
  • "Metrics: Population Attributable Fraction (PAF)". Health statistics and health information systems. World Health Organization. 
  • "National and regional story (Netherlands) - Environmental burden of disease in Europe: the EBoDE project". National and regional story. European Environment Agency (EEA). 
  • Öberg, Mattias; Jaakkola, Maritta S.; Woodward, Alistair; Peruga, Armando; Prüss-Ustün, Annette (26 November 2010). "Worldwide burden of disease from exposure to second-hand smoke: a retrospective analysis of data from 192 countries" (PDF). World Health Organization. 
  • Prüss, Annette; Havelaar, Arie (2001). Fewtrell, Lorna; Bartram, Jamie, eds. "The Global Burden of Disease study and applications in water, sanitation and hygiene". Water Quality: Guidelines, Standards and Health. London: IWA Publishing. 
  • "The WHO guides on assessing the environmental burden of disease" (PDF). World Health Organization. 

References

  1. ^ Prüss-Üstün, Annette; Corvalán, Carlos (2006). "Preventing disease through healthy environments: Towards an estimate of the environmental burden of disease" (PDF). Quantifying environmental health impacts. World Health Organization. 
  2. ^ a b c d e f g Kay, David; Prüss, Annette; Corvalán, Carlos (23–24 August 2000). "Methodology for assessment of Environmental burden of disease" (PDF). ISEE session on environmental burden of disease. Buffalo. 
  3. ^ a b c d e f g h Prüss-Üstün, Annette; Mathers, C.; Corvalán, Carlos; Woodward, A. (2003). Assessing the environmental burden of disease at national and local levels: Introduction and methods. WHO Environmental Burden of Disease Series 1. Geneva: World Health Organization.  
  4. ^ "Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013". The Lancet. 8 June 2015.  
  5. ^ a b c d e Knol, Anne B.; Petersen, Arthur C.; van der Sluijs, Jeroen P.; Lebret, Erik (1 January 2009). "Dealing with uncertainties in environmental burden of disease assessment". Environmental Health 8 (1): 21.  
  6. ^ Briggs, D. (1 December 2003). "Environmental pollution and the global burden of disease". British Medical Bulletin 68 (1): 1–24.  
  7. ^ a b Martin J Prince, Fan Wu, Yanfei Guo, Luis M Gutierrez Robledo, Martin O'Donnell, Richard Sullivan, Salim Yusuf (2015). "The burden of disease in older people and implications for health policy and practice". The Lancet 385 (9967): 549–562.  
  8. ^ World Health Organization (WHO) (2004). "Disease incidence, prevalence and disability" (PDF). The Global Burden of Disease 3. Retrieved 2009-01-30. 
  9. ^ Vos, T (Dec 15, 2012). "Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010". Lancet 380 (9859): 2163–96.  
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  11. ^ a b c d "Standard DALYs (3% discounting, age weights): WHO subregions (YLL)" (XLS). Disease and injury regional estimates for 2004. World Health Organization. 
  12. ^ a b "About the Global Burden of Disease (GBD) project". Health statistics and health information systems. World Health Organization. 
  13. ^ a b "Global burden of disease". World Health Organization. 
  14. ^ a b "What is the environment in the context of health?" (PDF). Environmental burden of disease series. World Health Organization. 
  15. ^ a b Department of Public Health and Environment (2010). "Quantification of the disease burden attributable to environmental risk factors" (PDF). Programme on quantifying environmental heath impacts. World Health Organization. 
  16. ^ Öberg, M.; Jaakkola, M.S.; Prüss-Üstün, A.; Schweizer, C.; Woodward, A. (2010). "Second-hand smoke: Assessing the environmental burden of disease at national and local levels". Environmental Burden of Disease Series 18. World Health Organization. 
  17. ^ a b c Knol, A.B.; Staatsen, B.A.M. (8 August 2005). "Trends in the environmental burden of disease in the Netherlands, 1980–2020" (PDF). National Institute of Public Health and the Environment. 
  18. ^ Fewtrell, Lorna; Prüss-Üstün, Annette; Bos, Robert; Gore, Fiona; Bartram, Jamie (2007). "Water, sanitation and hygiene: quantifying the health impact at national and local levels in countries with incomplete water supply and sanitation coverage" (PDF). WHO Environmental Burden of Disease Series 15. World Health Organization. 
  19. ^ a b Wigmore, Cameron (2 November 2007). "Study: Environmental burden of disease in Canada". 
  20. ^ Garrett, Laurie (1 January 2007). "The Challenge of Global Health" (PDF). Foreign Affairs 86 (January/February 2007): 14–38.  
  21. ^ Thacker, Stephen B; Stroup, Donna F; Carande-Kulis, Vilma; Marks, James S; Roy, Kakoli; Gerberding, Julie L (2006). "Measuring the Public's Health". Public Health Reports 121 (1): 14–22.  

Notes

Disease burden methodologies such as DALYs also do not capture other aspects of disease and illness, such as pain and suffering, deterioration in quality of life, and emotional and physical impacts on families.[21]

DALYs are a simplification of a complex reality, and therefore only give a crude indication of environmental health impact. Relying on DALYs may make donors take a narrow approach to health care programs. Foreign aid is most often directed at diseases with the highest DALYs, ignoring the fact that other diseases, despite having lower DALYs, are still major contributors to disease burden. Less-publicized diseases thus have little or no funding for health efforts. For example, maternal death (one of the top three killers in most poor countries) and pediatric respiratory and intestinal infections maintain a high disease burden, and safe pregnancy and the prevention of coughs in infants do not receive adequate funding.[20]

Criticism

Exposure to environmental hazards may cause chronic diseases, so the magnitude of their contribution to the Canada's total disease burden is not well-understood. In order to give an initial estimate of the environmental burden of disease for four major categories of disease, the EAF developed by the WHO, EAFs developed by other researchers, and data from Canadian public health institutions were used.[19] Results showed a total of 10,000–25,000 deaths, with 78,000–194,000 hospitalizations; 600,000–1.5 million days spent in hospital; 1.1–1.8 million restricted activity days for sufferers of asthma; 8000–24,000 new cases of cancer; 500–2,500 babies with low birth weights; and C$3.6–9.1 billion in costs each year due to respiratory disease, cardiovascular illness, cancer, and congenital affliction associated with adverse environmental exposures.[19]

Canada

Among the investigated factors, long-term PM10 exposure have the greatest impact on public health. As levels of PM10 decrease, related disease burden is also expected to decrease. Noise exposure and its associated disease burden is likely to increase to a level where the disease burden is similar to that of traffic accidents. The rough estimates do not provide a complete picture of the environmental health burden, because data are uncertain, not all environmental-health relationships are known, not all environmental factors have been included, and it was not possible to assess all potential health effects. The effects of a number of these assumptions were evaluated in an uncertainty analysis.[17]

In the Netherlands, air pollution is associated with respiratory and cardiovascular diseases, and exposure to certain forms of radiation can lead to the development of cancer. Quantification of the health impact of the environment was done by calculating DALYs for air pollution, noise, radon, UV, and indoor dampness for the period 1980 to 2020. In the Netherlands, 2–5% of the total disease burden in 2000 could be attributed to the effects of (short-term) exposure to air pollution, noise, radon, natural UV radiation, and dampness in houses. The percentage can increase to up to 13% due to uncertainty, assuming no threshold.

The Netherlands

Representative examples

Generally, it is not possible to estimate a formal confidence interval, but it is possible to estimate a range of possible values the environmental disease burden may take based on different input parameters and assumptions.[2][3][5] When more than one definition has to be made about a certain element in the assessment, multiple analyses can be run, using different sets of definitions. Sensitivity and decision analyses can help determine which sources of uncertainty affect the final results the most.[5]

When estimating the environmental burden of disease, a number of potential sources of error may arise in the measure of exposure and exposure-risk relationship, assumptions made in applying the exposure or exposure-risk relationship to the relevant country, health statistics, and, if used, expert opinions.

Uncertainty

Necessary data include prevalence data, exposure-response relationships, and weighting factors that give an indication of the severity of a certain disorder. When information is missing or vague, experts will be consulted in order to decide which alternative data sources to use. An uncertainty analysis is carried out so as to analyze the effects of different assumptions.[17]

DALYs = number of people with the disease × duration of the disease (or loss of life expectancy in the case of mortality) × severity (varying from 0 for perfect health to 1 for death)

The public health impacts of air pollution (annual means of PM10 and ozone), noise pollution, and radiation (radon and UV), can be quantified using DALYs. For each disease, a DALY is calculated as:

Implementation and interpretation

Environmental burden of disease for selected risk factors
This presents the yearly burden, expressed in deaths and DALYs, attributable to: indoor air pollution from solid fuel use; outdoor air pollution; and unsafe water, sanitation, and hygiene. Results are calculated using the exposure-based approach.
Total environmental burden of disease for the relevant country
The total number of deaths, DALYs per capita, and the percentage of the national burden of disease attributable to the environment represent the disease burden that could be avoided by modifying the environment as a whole.
Environmental burden by disease category
Each country summary was broken down by the disease group, where the annual number of DALYs per capita attributable to environmental factors were calculated for each group.[3]

In 2002, the WHO estimated the global environmental burden of disease by using risk assessment data to develop environmentally attributable fractions (EAFs) of mortality and morbidity for 85 categories of disease.[2][3][18] In 2007, they released the first country-by-country analysis of the impact environmental factors had on health for its then 192 member states. These country estimates were the first step to assist governments in carrying out preventive action. The country estimates were divided into three parts:

A dose-response relationship is a function of the exposure parameter assessed for the study population.[2] Exposure distribution and dose-response relationships are combined to yield the study population's health impact distribution, usually expressed in terms of incidence. The health impact distribution can then be converted into health summary measures, such as DALYs. Exposure-response relationships for a given risk factor are commonly obtained from epidemiological studies.[2][3] For example, the disease burden of outdoor air pollution for Santiago, Chile was calculated by measuring the concentration of atmospheric particulate matter (PM10), estimating the susceptible population, and combining these data with relevant dose-response relationships. A reduction of particulate matter levels in the air to recommended standards would cause a reduction of about 5,200 deaths, 4,700 respiratory hospital admissions, and 13,500,000 days of restricted activity per year, for a total population of 4.7 million.[2]

The exposure-based approach, which measures exposure via pollutant levels, is used to calculate the environmental burden of disease.[17] This approach requires knowledge of the outcomes associated with the relevant risk factor, exposure levels and distribution in the study population, and dose-response relationships of the pollutants.

The WHO developed a methodology to quantify the health of a population using summary measures, which combine information on mortality and non-fatal health outcomes. The measures quantify either health gaps or health expectancies; the most commonly used health summary measure is the DALY.[2][13][15]

Estimation

Certain environmental factors were excluded from this definition:

To measure the environmental health impact, environment was defined as "all the physical, chemical and biological factors external to a person, and all the related behaviours".[14] The definition of modifiable environment included:

In 2006, the WHO released a report which addressed the amount of global disease that could be prevented by reducing environmental risk factors.[5] The report found that approximately one fourth of the global disease burden, and more than one third of the burden among children, was due to modifiable environmental factors. The "environmentally-mediated" disease burden is much higher in developing countries, with the exception of certain non-communicable diseases, such as cardiovascular diseases and cancers, where the per capita disease burden is larger in developed countries. Children have the highest death toll, with more than 4 million environmentally-caused deaths yearly, mostly in developing countries. The infant death rate attributed to environmental causes is also 12 times higher in developing countries. 85 out of the 102 major diseases and injuries classified by WHO were due to environmental factors.[5]

Modifiable risk factors

The first study on the global burden of disease, conducted in 1990, quantified the health effects of more than 100 diseases and injuries for eight regions of the world, giving estimates of morbidity and mortality by age, sex, and region. It also introduced the DALY as a new metric to quantify the burden of diseases, injuries, and risk factors.[3][12][13] In 2000–2002, the 1990 study was updated to include a more extensive analysis using a framework known as comparative risk factor assessment.[12]

History

Disease category Percent of all YPLLs, worldwide[11] Percent of all DALYs, worldwide[10] Percent of all YPLLs, Europe[11] Percent of all DALYs, Europe[10] Percent of all YPLLs, US and Canada[11] Percent of all DALYs, US and Canada[10]
Infectious and parasitic diseases, especially lower respiratory tract infections, diarrhea, AIDS, tuberculosis, and malaria 37% 26% 9% 6% 5% 3%
Neuropsychiatric conditions, such as depression 2% 13% 3% 19% 5% 28%
Injuries, especially motor vehicle accidents 14% 12% 18% 13% 18% 10%
Cardiovascular diseases, principally heart attacks and stroke 14% 10% 35% 23% 26% 14%
Premature birth and other deaths (infant mortality) 11% 8% 4% 2% 3% 2%
Cancer 8% 5% 19% 11% 25% 13%

In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury.[10][11]

Statistics

Contents

  • Statistics 1
  • History 2
  • Modifiable risk factors 3
  • Estimation 4
  • Implementation and interpretation 5
    • Uncertainty 5.1
  • Representative examples 6
    • The Netherlands 6.1
    • Canada 6.2
  • Criticism 7
  • Notes 8
  • References 9

:549[7] According to an article in The Lancet published in November 2014, disorders in those aged 60 years and older represent "23% of the total global burden of disease" and leading contributors to disease burden in this group in 2014 were "cardiovascular diseases (30·3%), malignant neoplasms (15·1%), chronic respiratory diseases (9·5%), musculoskeletal diseases (7·5%), and neurological and mental disorders (6·6%)."[9].lower back pain in 2010, it was [8];unipolar depression – YPLL) measures the years of what could have been a healthy life that were instead spent in states of less than full health. In 2004, the health issue leading to the highest YLD for both men and women was years of potential life lost (YLD) (or years lost due to disability For example, [3]

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