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GIS > GIS29 Geography, Migration, Development And Disease Burden > Flashcards

GIS29 Geography, Migration, Development And Disease Burden Flashcards

1
Q

Disease burden

A

**Assessing health impact of a disease **quantitatively at ***population level

Potential uses:

  • compare ***disease burden over time / between places / and person
  • compare ***health losses due to different risk factors / disease states
  • identify ***priority actions
  • estimate Clinical / ***cost-effectiveness of interventions
  • guide ***policies and strategies adoption and implementation
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2
Q

Measuring health events

A
  1. Fatal events
    - mortality
  2. Non-fatal events
    - hospital care
    - primary care
  3. Summary measure of both
    - Quality-adjusted life years (QALYs)
    - Disability-adjusted life years (DALYs)
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3
Q

Measuring mortality

A
  1. Mortality rate
    - Number of deaths in a population, scaled to the size of that population, ***per unit of time
    - e.g. deaths per 1000 individuals per year
  2. Crude death rate
    - Total number of deaths per year per 1000 population at risk of dying in the middle of the year
    - Without considering cause of death
    - Overall impression in a single figure
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4
Q

Specific / stratified mortality rates

A
  1. Sub-population specific rates
    - Age-specific
    - Sex-specific
    - rate of death occurring **in a subgroup of the population
    - used when crude rate inadequate to describe **    conditions having different load in population subgroups
  2. Cause/ disease-specific
    - death rate for a ***specific cause of death
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5
Q

Standardised rates

A
  1. Age / sex standardised rate
    - Take account of the **different age / sex structures of 2 populations
    —> eliminate effect of the characteristic being standardised
    —> factors being standardised can no longer be used to explain variations
    - Allow for **    direct comparison of mortality experience across different geographical areas / over time
  2. Direct standardisation
    - a common age-structured population —> observe the rate
  3. Indirect standardisation
    - a common set of age-specific rates —> observe the population
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6
Q

Measures of morbidity

A
  1. Health care utilisation data
    - hospital-based data
    - primary care data
  2. Surveillance data
    - ILI-surveillance systems
  3. Registration of disease
    - Cancer registry
  4. Population-based health information
    - General household survey / local health surveys
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7
Q

Problems of traditional assessments of the number of disease burden

A

Measured either

  • the number of deaths
  • the amount of suffering (impaired QOL) due to disease incidence
  • but NOT both

Make it difficult to compare:
- losses that **occur at different ages
- conditions having **differential impact on length / QOL
—> some conditions do not markedly shorten life but reduce QOL
—> some conditions do shorten life but also reduce QOL

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8
Q

Examples of inadequacy of traditional health indicators

A
  • death at age 20 years vs death at age 70 years
  • 200 acute respiratory infections vs 400 cases of infectious diarrhoea
  • cancer treatment resulting in an average survival of 10 years compared to untreated average survival of 2 years = gain of 8 whole years of life per person treated?
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9
Q

Other health indicators

A
  • Focusing on either mortality / morbidity
    —> Life expectancy
  • Combining data on mortality and non-fatal outcomes into a single number
    —> Disability-adjusted life years (DALYs)
    —> Quality-adjusted life year (QALY)
    —> Disability-adjusted life expectancy (DALE)
    —> Healthy life year (HeaLY)
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10
Q

Life expectancy

A

Life expectancy:
- Average no. of years an individual of a given age is expected to live if current mortality rates continue to apply
—> a statistical abstraction based on existing age-specific death rates (assuming mortality at each age remains constant in the future)
—> a hypothetical measure and indicator of current health and mortality condition

Life expectancy at birth:

  • average no. of years a newborn baby can be expected to live
  • average no. of years to be lived by a group of people born in the same year
  • a measure of overall QOL in a country and summarises mortality at all ages

Life expectancy at a given age:
- average no. of ADDITIONAL years a person of age X will live, based on the age-specific death rates for a given year if current mortality trends continue to apply

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11
Q

Relationship between life expectancy and GDP

A

↑ GDP —> ↑ life expectancy

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12
Q

***Quality-adjusted life year (QALY)

A

Adjust life years for QOL
—> a single measurement of changes in QOL relative to a state of perfect wellbeing (valued as unity)

***QALY = Life years x Quality of life weight(0-1)

QOL: pain / mood / self-care ability / social activities / household activities / paid employment

Uses:

  • comparison of clinical and cost-effectiveness of different interventions (pharmaceuticals, procedures, programmes)
  • adopted by NICE in UK

Problems:

  • theoretical and practical difficulties of deriving valid indices of QOL
  • reservation regarding the fairness and appropriateness for using as a basis for assessing / determining health needs
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13
Q

***Disability-adjusted life years (DALYs)

A
  • summary measure of population health by combining mortality and disability
  • combines in one measure:
    —> Time lost due to premature mortality + Time lost due to disability
    —> “Time” (years) lost as the unit of measurement
    —> measures Health Gap: relative to an “ideal” life expectancy (80 years for men and 82.5 years for women)

***DALY = YLL + YLD

YLL: years of life lost due to premature mortality
YLD: years of life lost due to disability

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14
Q

***YLL: years of life lost due to premature mortality

A

YLL, for a given cause, age, sex:

***YLL = N x L

N: no. of deaths
L: standard life expectancy at age of death (in years)

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15
Q

***YLD: years of life lost due to disability

A

***YLD = I x L x DW

YLD: years lived with disability
I: no. of incident disability cases
DW: disability weight (reflect severity of disease on a scale 0 (perfect health) to 1 (dead))
L: average duration of disability (years)

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16
Q

Age weights

A
  • Social preference of value of year lived by a young adult

—> a year of life in young adulthood worth more than a year lived by young child / old aged

17
Q

Time discounting

A

People’s preference on a healthy year of life immediately rather than in the future

3% time discount rate added to every year of life lost in the future
—> estimate net present value of years of life lost

18
Q

Global disease burden

A

Death: CD ~ NCD
YLL: CD&raquo_space; NCD
YLD: CD &laquo_space;NCD
DALY: CD ~ NCD

19
Q

Contributors to global DALY in different age groups

A

Neonates:
- Neonatal disorder (NND)

Children:
- GE (GI infection)

Adult:

  • Mental + other NCD + TA
  • HIV

Old age:

  • MSD (musculoskeletal) + DM + other NCDs
  • IHD + Cancer
20
Q

Temporal pattern of GDB over last few decades

A
  1. Changing proportions of DALYs by different age groups
    —> ↓ proportion of DALY by <5
    —> ↑ proportion of DALY by 15-69
    (disease more affect elderly now)
  2. Overall decline in global age-specific mortality rate
    —> huge decline in neonatal MR, smaller decline in adult MR
  3. % change in no. of deaths by country
    —> children <5: ↓ no. of deaths for most developing regions apart from sub-Saharan Africa
    —> young adults (15-49): ↑ no. of deaths in Botswana, South Africa, Zambia, and Zimbabwe by >500%
    (Only small amount attributed to larger population size, mostly due to rapid increases in HIV/AIDS mortality
  4. Change in global cause of death (deaths per 100,000)
    - CD: generally ↓ (except HIV/AIDS)
    - NCD: generally ↑
  5. Change in global DALYs
    - CD: generally ↓ (except HIV/AIDS)
    - NCD: generally ↑
  6. Change in global YLD
    - Mainly due to NCD
21
Q

Geo-temporal pattern of GDB over last few decades

A
  1. DALYs
    - Developed countries (high SDI: socio-demographic index):
    —> Mainly NCD, generally remained similar
    - Developing countries (low SDI):
    —> Mainly CD, with some NCD ↑
  2. Death
    - Developed:
    —> Mainly NCD, generally remained similar
    - Developing:
    —> Mainly CD but generally ↓, with some NCD ↑
  3. YLL
    - Developed:
    —> Mainly NCD, with some NCD ↑
    - Developing:
    —> Mainly CD, with some NCD ↑
  4. YLD
    - Developed:
    —> Mainly NCD, generally remained similar
    - Developing:
    —> Mainly ***NCD, generally remained similar
  5. China DALYs
    - CD: generally ↓
    - NCD: generally ↑
  6. China YLDs
    - Young age: Nutritional deficiencies
    - Adult / elderly: Mental / COPD / MSD / other NCD
22
Q

Major temporal trends in GDB

A
  1. Since 1970, globally, Men and women:
    - gained slightly more than 10 years of life expectancy overall
    - but spend more years living with illness and disability
  2. Broad shift from communicable, maternal, neonatal, nutritional causes towards NCD
  3. Infectious diseases, maternal and child illness, malnutrition now cause fewer deaths and less illness than 20 years ago
    —> fewer children dying every year
  4. NCD (heart disease, cancer) become dominant causes of death and disability worldwide
    —> but more young and middle-aged adults are dying and suffering from disease and injury
23
Q

General global epidemiological transition

A
  • Majority of global mortality contributed by ***developing countries
  • Marked ***regional heterogeneity exists in many causes (e.g. violence, suicide, liver cancer, DM)
  • Many developing countries suffer from ***“Double disease burden”
    —> communicable, maternal, neonatal and nutritional deficiencies remain dominant causes of disease burden (YLL and DALY)
    —> increasing burden from NCDs
24
Q

Geographical distribution and reasons for occurrence of different communicable and non-communicable GI diseases
—> Infantile diarrhoea

A

Incidence / prevalence of childhood diarrhoea varies >10-fold across geographic areas (very high in central Africa, very low in Japan)

Major risk factor for infantile diarrhoea

  • poor sanitation
  • lack of clean food and water
  • poverty

Treatment:

  • ORS
  • zinc tablets

Prevention:

  • increase clean water and safe sanitation
  • promote hygiene education and practice
  • exclusive breastfeeding
25
Q

Geographical distribution and reasons for occurrence of different communicable and non-communicable GI diseases
—> Colorectal cancer

A

Geographical distribution:
- Incidence of CA colon varies >20 fold across geographic areas
- 2nd most common cancer in developed countries
- Relatively rare in developing countries
—> more towards either a lifestyle / environmental / genetic factor

Temporal changes in disease risk:
- Incidence rates ↑ rapidly in some countries with formerly low rates
- level of risk experienced changes with time
- migrants quickly acquire cancer pattern of host country
—> more towards either a ***lifestyle / environmental rather than genetic factor (meat consumption ↑ —> ↑ colon cancer incidence)

26
Q

Geographical distribution and reasons for occurrence of different communicable and non-communicable GI diseases
—> Hepatocellular carcinoma

A

Geographical distribution

  • Incidence of HCC varies >12-fold across geographical areas
  • 80% of cases in ***developing countries
  • uncommon in where hepatitis is not endemic (where mostly metastasis CA)
  • correspond closely with patterns of ***hepatitis B endemicity
27
Q

Risk factors and prevention for HCC

A

Hep B/ Hep C
- percutaneous blood exposure
—> main-line drug addict
—> blood transfusions
- unprotected sexual intercourse (MSM: men who have sex with men)
- vertical transmission from mother to infant

Prevention of Hep B transmission in HK
- public health programs
—> universal newborn vaccination (major factor)
—> screening of blood products for HBV
—> antenatal screening of Hep B infection in pregnant women
- behavioural approach
—> avoid sharing / reuse of needles
—> use of condom / safe sex
28
Q

Endemicity of Hep B in China

A
  • Highly endemic for chronic Hep B infection
  • estimated 130 million HBV carrier
  • most cases of acute Hep B infection occur in perinatal / early childhood period
  • incidence of HBV still ↑ despite vaccination programme since 1990s
  • 1 million new cases in 2005
29
Q

Summary: QALY, DALY, YLL, YLD

A
  1. QALY = Life years x QOL weight (0-1)
  2. DALY = YLL + YLD
  3. YLL = N x L
    (N: no. of deaths, L: standard life expectancy at age of death (in years))
  4. YLD = I x L x DW
    (I: no. of incident disability cases
    L: average duration of disability (years)
    DW: disability weight (reflect severity of disease 0-1))

GIS (29 decks)

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