PPS Risks and Trends in Asthma Flashcards
Descriptive epidemiology
First stage of epidemiological investigation focusing on how disease risk varies in relation to place, time and person
What does descriptive epidemiology use?
Routinely collected information especially deaths (mortality) where possible, but for diseases that don’t cause many deaths like asthma, ad hoc population surveys needed
Asthma definition
Biological: A disorder characterised by narrowing of airways, which varies with time, either spontaneously or as a result of treatment - at least in initial stages. Pathological changes include chronic inflammation of the airways, with bronchial hyperresponsiveness to a wide variety of stimuli.
Clinical: Wheeze and dyspnoea (breathlessness), often associated with cough, that varies over time. May be clearly associated with various precipitating factors. Responds to anti-asthmatic treatment. May progress to persistent chronic symptoms similar to chronic obstructive pulmonary disease (COPD)
Social: variable effects – loss of school/work and social interaction in severe cases
How does knowing about variations in disease between places, times and persons help us?
helps to understand important aspects of disease
whether a disease is inevitable’ (or preventable)
what represents biological normality’
helps to establish disease causes
helps to separate environmental from genetic causes
helps to establish needs for treatment and prevention
helps in making diagnosis from a particular clinical presentation
What did Hippocrates state on variations in disease risk between places?
where people live can affect their health
`.…consider the situation (of a place)….the winds….the waters….and the mode in which the inhabitants live….whether they are fond of eating and drinking to excess….or are fond of exercise and labour….’
Geographic variations in disease risk…
affect many diseases and can be very large
can occur between countries and within countries (between regions or between very small areas)
How does asthma prevalence vary in different countries?
2003 study- higher prevalence in western countries, highest in the UK then Aus/NZ and US/Canada
What does the high variation of asthma across different countries tell us?
High rates in UK not inevitable, should be scope for prevention
Low rates like in Indonesia may be closer to biological normality
How can geographical variation indicate biological normality?
Eg. CHD shows a lot of variation across countries, post-mortems in high risk countries show atherosclerosis vs clean and open coronary arteries in less affected countries. So this varies between different settings.
How can variations in disease risk between places allow the study of disease causes?
Simple mapping of disease in relation to possible cause
Ecological studies for causes of non-infections diseases
Ecological study
Used to investigate geographical variation and disease
Unit of observation is population or community instead of individual
Both exposures and disease rates are measured in each of a series of geographical populations and their relation is examined (works best in context where disease risks vary widely)
