Measuring Health and Disease

Question 1

why do we measure population health?

Answer 1

Find out disease prevalence (how common) & incidence (how many new cases)
We can then see if interventions or policies to improve health and reduce ill-health are having any effect
Identify differences in disease patterns between different population groups or locations to then provide help where it is most needed
Service planning –do we have the right services in right place for right people?

Question 2

what were the major causes of death in the UK 2018?

Answer 2

Major causes are non-communicable long-term diseases e.g. dementia and Alzheimer’s
The only communicable diseases were influenza and pneumonia.

Question 3

what were the major causes of death in the UK 1915- 2015?

Answer 3

Infectious disease was the main cause of death until around 1945 - Antibiotics came in 1940s greatly reducing the number of people dying as a result of them.
Breast Cancer in women, and heart conditions in men took its place
Shows transition from death being predominantly being due to infectious disease to non-communicable long-term conditions

Question 4

what were the major causes in death in high income communities compared to low income communities?

Answer 4

HIC: main causes are non-communicable disease e.g. heart disease, stroke COPD etc.
LIC: most are communicable diseases e.g. HIV/AIDS lower respiratory infections,

Question 5

what is the difference in life expectancy in 1870 compared to 2001?
why has it improved?

Answer 5

1870 – 42
2001 - 78
Majority of this improvement was due to better sanitation, better housing and food and preventative measures. Health care did not have a significant role

Question 6

how do you measure health status of a whole country?

Answer 6

Census
every 10 years, counts everyone in a household on one particular night, collects age, gender, education, marital status etc.
Sometimes there is a question on health e.g. how would you rate your health 1-5?
Data from census is used to create a population pyramid

Death certification
legal requirement to register death; age, sex and occupation (not ethnicities); primary cause listed; secondary causes given also (any contributing diseases)

Question 7

what is a population pyramid?

Answer 7

a graphical illustration of the distribution of a population by age groups and sex; it typically takes the shape of a pyramid when the population is growing.

HIC: Bulge in middle age show key sign for aging population (square)
LIC: Triangular shaped population pyramid - large number of children/teens due to high birth but high death rate in older population means it tapers very rapidly

Question 8

what is the health survey for England (HSE)?

Answer 8

Around 8,000 adults and 2,000 children take part in the survey each year (since 1990). Information is collected through an interview and, if participants agree, a visit from a specially trained nurse.
Contains questions about demographic info, smoking status, self-reported information on health, illness, treatment, health service usage. Blood and saliva sample analysis, height/weight
Additional information on key theme each year e.g. CVD asthma, accidents, exercise).
Freely available online

Question 9

what is the general lifestyle survey?

Answer 9

sample from whole of GB
Contains question about demographic info about households families and people, housing tenure/accommodation, vehicle access, employment, education, health & service usage, smoking & drinking, family info (i.e. marriage, fertility)

Question 10

what is the Hospital Episode Statistics?

Answer 10

(health service usage) Secondary care
details of all NHS hospital admissions and all outpatient appts in England (started in 1989)
secure details on diagnoses, operations, age, gender, ethnicity, time waited & date of admission, geographical info on where treated, Outcome: discharge home, care home, death.

Question 11

what is Clinical Practice Research Database – CPRD and THIN?

Answer 11

(Primary Care)
anonymised longitudinal data from 625 GP surgeries – 5 million patients
clinical research planning, drug utilisation, studies of treatment patterns, clinical epidemiology, drug safety, health outcomes, health service planning
Being linked to hospital data

Question 12

how do we collect Health protection reports of notifiable diseases?

Answer 12

diseases we’re immunised against (GI diseases eg. Salmonella) (STD) (E.g. Yellow fever, TB, MMR, Cholera, Anthrax etc.)
Certain infectious diseases notified by doctors
Laboratory results for some infectious diseases notified
Cancers registered in cancer registries and linked to mortality data

Question 13

what are other ways you can collect health data from a population?

Answer 13

national/regional/local audits or surveys

Question 14

how can you see how many people died of a disease?

Answer 14

you would use death certificate information as it shows you all deaths whereas hospital episode statistics only shows death in hospitals.

Question 15

Answer 15

Death Certification

Question 16

Answer 16

Either Death Certification & Census or Hospital Episode

Question 17

what are the three commonly-used methods of calculating birth or fertility rates?

Answer 17

birth rate, fertility rate, general fertility rate

Question 18

what is birth rate?

Answer 18

Birth rate = number of live births per 1000 population (all ages and sexes)

Question 19

what is the general fertility rate?

Answer 19

General fertility rate = number of live births per 1000 women aged 15-44

Question 20

what is total fertility rate?

Answer 20

Total fertility rate = the average number of children that a woman would bear if they experienced the age-specific fertility rates at that point in time.

Question 21

how do you use BR, GFR, and TFR to measure birth and fertility rates?

Answer 21

Total fertility rate is often used in preference to the general fertility rate as it allows for comparisons to be made over time or between areas after taking into consideration differences in age-structure between populations.
In the UK, fertility rates are highest in the 30-34 age category. If you compared an area with a high proportion of women aged 25 to 29 with an area with a high proportion of women aged 30-34 you might find that the second area had a higher general fertility rate than the first. But this difference may well standardise out over time as more women in the first area reached the 30 to 34 age category and started to have children.

Question 22

define prevalence

Answer 22

proportion of people in a population who have a particular disease at a specific point in time/over specified time period. It is useful for ascertaining the burden of long-term conditions.

Question 23

what is point prevalence?

Answer 23

equation (see below) Often reported as % or x/100,000 population
Useful for planning services

Question 24

what is incidence?

Answer 24

Number of new cases over a period of time in a population.
The measure of incidence most commonly used is the incidence rate.
The incidence rate represents the rate of development of disease in a population.

Question 25

how do you calculate incidence rate?

Answer 25

Person-years at risk = total population at risk x time period
Person-years at risk is the sum, over all individuals, of the number of years that each individual is followed-up in a study or at risk.
1 person-year at risk = 1 individual at risk (or observed) for 1 year, OR 2 individuals at risk (or observed) for 6 months each OR 4 individuals at risk (or observed) for 3 months each etc.
Person-year at risk can be approximated as the population at the mid-point of the time period.

Question 26

how do you calculate infant mortality rate?

Answer 26

Question 27

Why do we measure the IMR?

Answer 27

The IMR is highly correlated with expectation of life, and with overall economic status
High infant mortality rates are amenable to change through public health measures (e.g. care of pregnant women, supporting breastfeeding, infant immunisation & nutrition programmes)

Question 28

how do you calculate crude mortality rate?

Answer 28

If there were 5000 deaths in 1 year in a population of 1 million people at its mid-point
Crude mortality rate = 5000/1,000,000
= 5 deaths/ 1000 resident pop. per year
Be careful as can be confusing as they don’t take into account the structure of population

Question 29

how do you calculate disease specific death rate?

Answer 29

Can also have age specific rate or sex-specific rates for disease or death
Mortality data - legal requirement in UK for each death to be registered

Question 30

what are the pros and cons of using mortality data for as a measure of population health?

Answer 30

Advantages:
Legal requirement in UK to register each death (complete data)
little delay in data collection
cheap source of health data (legal requirement for death certificates in UK)
international classification of diseases - ensures comparability
Disadvantages:
potential for error (diagnosis, certification, coding, processing, interpretation etc.)
death may result from conjunction of diseases
Some diseases have high mortality rate but quick death occurs; others are long-term, resource-intensive but rarely directly cause death (difficult for resource allocation – The biggest killer shouldn’t necessarily have most allocated to it.)

Question 31

how might we use mortality or morbidity rates?

Answer 31

Compare areas:
To identify areas where people experience poor health
Identify the need for preventive services
May raise hypotheses about the cause of a disease
Look at change over time to see if preventative strategies are working.

Question 32

what does Standardisation allow?

Answer 32

more accurate comparisons to be made and avoid false conclusions
Standardisation enables us to compares rates of disease or death in populations with different structures, be it age, sex or ethnicity.

Question 33

what is direct standardisation?

Answer 33

age-specific rates from a study population applied to standard population structure
Allows you to see what would be the death rate in the standard population if it had the age and sex-specific death rates experienced by the population I am looking at?
e.g e.g age- specific rates of bournmouth applied to UK

Question 34

what are the pros and cons of direct standardisation?

Answer 34

advantages
compare disease rates across areas & time frames
disadvantages
requires age-specific rates 🡪 not always available at local level
rates may not be stable for a small number of events (<100)

Question 35

what is indirect standardisation?
how do you calculate SMR?

Answer 35

age-specific rates from standard population applied to study population (standardised mortality ratio)
e.g age- specific rates of UK applied to bournmouth

Question 36

what does an SMR of 150% mean?

Answer 36

SMR of 150% means that your study population has 1.5 times as many deaths as you would expect

Question 37

what are the pros and cons of SMR?

Answer 37

advantages:
doesn’t require local rates, only absolute no. of events
interpretation easier
disadvantages:
areas cannot be directly compared
doesn’t give idea of burden of disease (because it is a ratio not full figures)

Question 38

why is SMR used?

Answer 38

can compare SMRs for a disease w/ the national average (i.e. 100)
identify diseases that have higher than national rates in an area & need investigation
consider preventative measures
may raise hypotheses about the cause of a disease

Question 39

what are the pitfalls in interpreting health and disease?

Answer 39

Different criteria used to define the disease between areas
Not all the cases of disease have been identified in each area
Use of hospital data to describe disease or death in an area (omits people who are treated in general practice or die in the community)

Question 40

how does deprivation affect health?

Answer 40

those living in socio-economically deprived areas have lower life expectancy, higher mortality rates from most conditions, higher teenage pregnancy rates, higher levels of unhealthy lifestyles
Gini coefficient measures distribution of income within a population - measure of economic inequality

Question 41

what are the theories as to why health may be associated with socioeconomic deprivation?

Answer 41

Artefact = observed associations are not genuine but exist due to methods of measuring health and deprivation NO effect
Social selection = health determines socio-economic status rather than vice versa (i.e. poor health 🡪 less likely to work 🡪 more ‘deprived’)
Behavioural/cultural = those in deprived areas more likely to smoke, eat poor diets, not exercise, less capital, crime etc.
Psychosocial = stress of working in poorly paid, low status jobs w/ little autonomy 🡪 biological changes in body 🡪 create patho-physical changes i.e. stress causes your poor health
Material = direct effects of poverty, cold damp house more likely to end up with lung disease, dangerous area more likely injured