Public Health Key Data Sources

South West Public Health Observatory

Key Data Sources for Public Health Public Health Information and Evidence Seminar

Mark Dancox

4th November 2010


In this session

• Main sources of data used in Public Health

• Over-view of special methods used to measure the health of a population

• Specific data sources for the South West


First things first

• In public health we are often interested in the frequency, distribution and determinants of health problems and disease in populations.

• The unit of interest is the POPULATION not the individual.


What data do we use?

• Raw data, only available to NHS employees with appropriate role-based permissions:– Births – Deaths – Hospital Admissions– Cancer Registrations– GP consultations – Prescriptions – A&E attendances– Population

• Need to aggregate data so that it can’t be identified


What’s the distribution?

• Often want to tie in frequency information to location. • Consideration of geography is therefore important:

– Postcode– Lower Super Output Area– Local Authorities – Primary Care Trusts– Strategic Health Authorities

• Need to link geography information to births and deaths data

• Social Marketing datasets linkage


• Mortality – All cause– Specific cause– Place of death

• Life Expectancy – General measure of health– At birth – Disability Free

• Births– Birth Rate – Infant Mortality

Some common types of measures:


– Widely accepted system of classifying diseases and causes of death developed by the World Health Organisation.

– Updated every 10 years or so to keep up with advances in medical knowledge and improvements in methods of diagnoses.

– Changes in coding can present problems when looking at the occurrence of specific causes of death through time.

– ONS regularly produce data on mortality statistics using the ICD-10 system.

ICD-10


– Infectious and parasitic diseases– Neoplasms– Diseases of the blood and blood forming organs– Endocrinal and Nutritional diseases– Mental and behavioural disorders– Diseases of the circulatory system– Diseases of the respiratory system– Injury, poisoning and certain other causes of external

consequences

ICD-10 Headings include:


Hospital Admissions (HES)

• Principal source of data on all admissions to NHS hospitals in England.

• Data warehouse containing details of all admissions to NHS hospitals in England.

• Includes private patients treated in NHS hospitals, patients who were resident outside of England and care delivered by treatment centres (including those in the independent sector) funded by the NHS.

• Contains details of all NHS outpatient appointments in England


Determinants : Factors affecting health• Health is affected by many factors, as summarised by

Dahlgren and Whitehead’s diagram…


What are the determinants ?

• Age, sex and constitutional factors• Lifestyle • Agriculture and Food production• Education• Work Environment• Unemployment• Water and Sanitation• Health Care Services• Housing


Deprivation

• Prepared by DCLG• Area based measure based on seven ‘domains’

– Health and Disability– Income – Employment – Education skills and Training– Barriers to housing and services– Crime – Living Environment

• Applies to England• IMD2004 and IMD2007 available


Surveys

• Established surveys can provide information on the determinants of health– Health Survey for England– General Household Survey– Longitudinal Study– Active People – National Child Measurement Program


Health Survey for England

• Annual • Questionnaire-based answers with physical measurements

and analysis of blood samples. • Blood pressure, height and weight, smoking, drinking and

general health are covered every year.• An interview with each eligible person in the household is

followed by a nurse visit.


General Household Survey

• Information from people living in households in England • Annual • Data collected on

– household and family information – housing tenure and household accommodation – consumer durables including vehicle ownership – employment – education – health and use of health services – smoking and drinking – family information including marriage, cohabitation and fertility – income – demographic information about household members including

migration.


South West Observatory Modules

• Further information on the determinants of health can be found via the modules of the South West Observatory:– Economy– Skills and Learning– Planning – Environment– Crime – Culture

• State of the South West


Special methods of measuring public health• Published sources of Public Health data use different

methods of measuring the health of a population:– Incidence – Prevalence – Crude Rate– Standardised Rates – (confidence intervals)


Prevalence

Prevalence quantifies the proportion of individuals in a population who have the disease at a specific instant.

Total number of cases at a given timePrevalence = Total population at that time

Note: No time period is involved here.


Incidence

Incidence quantifies the number of new cases of disease that develop in a population of individuals at risk during a specified time period.

Number of new cases in period of timeIncidence =

Population at risk

The denominator, “population at risk” , should consist of the entire population in which new cases can occur.

Incidence and prevalence

Sick population

(Prevalence)Healthy

population

Incidence (new cases)

die (mortality)

recover


Crude Rate

• Is the number of cases in a population divided by the total population during a specific time interval.

• Provides information on the experience of the population.

• Useful for the allocation of health resources and public health planning.

• However if comparing heart disease rates between two populations where one population had a larger proportion of young people then differences in rates might simply reflect the relationship between heart disease and age.


Category-Specific Rates

• To account for different population distributions of a factor of interest we can present and compare category-specific rates.

• These are calculated on a subgroup of the population which is defined by stratifying the populations into categories e.g age.

• They permit comparisons between different categories within the same population.


Age standardisation

• Occurrence of disease in one area may appear to be higher than in another because:– Population structures are different– One area is older than another

• Standardisation used to adjust for the effects of age on mortality rates or other rates

• Direct or Indirect• Involves the calculation of numbers of expected

events which are then compared with numbers of observed events


Two Methods of standardisation

• Different methods available but ‘Direct’ and ‘Indirect’ methods are most common

• Can calculate confidence intervals for each• Which method used depends on the comparisons to be

performed and the availability of data


When to use which?

• No right or wrong approach, but…– Direct standardisation useful to compare different areas

or through time– Indirect Standardisation useful to determine if disease

incidence is high or low in one area.


Measures in action….Health Profiles


Measures in action….NCHOD

Thankyou

Mark [email protected]

Public Health Key Data Sources

Education

domains health

world health organisation

data warehouse

raw data

key data sources

session main sources

circulatory system diseases

england imd2004