Week 1 all-cause mortality Flashcards
Define all cause mortality
all of the deaths that occur in a population regardless of cause
How is all cause mortality assessed and what are the limitations?
Observational research
Cant talk about cause and effect (can only say there are relationships - could be confounding factors that explain the relationships).
Who is Prof Jeremy Morris? (1910-2009)
Used epidemiological methods in the 50s to look at heart disease.
Compared CHD in bus drivers and bus conductors.
Likelihood of heart attack was halved in the conductors and if heart attack did happen in conductors they were more likely to recover.
What was the purpose of the Harvard Alumni Health study? (Paffenbarger et al, 1986)
Set up to explore the causes, pathways and preventabilities of chronic degenerative disorders that remain largely unknown through the socio-medical science of epidemiology.
Outline the method of the Harvard Alumni Health study?
Male students 1916-50
Record deaths and causes and perform statistical analysis to look at relationships between how active people were and their likelihood of premature death
What were the results of the Harvard Alumni Health study?
The higher the PA index the lower the relative risk of death (up to PA index 3000-3499, then increases again but still higher than reference group).
Biggest drop is between <500 (inactive) and 500-899 so asking people who are doing nothing to do just a little is where we are likely to get the biggest benefits as a population.
Limitations of the Harvard Alumni Health study?
At very high PA index there probably isn’t many people in that group so ay not be that accurate/representative
Have to consider if there are other factors, e.g. people who are physically active tend to have better diet
Harvard students - all likely to be well off and socio-economic status impacts on mortality.
What does some research suggest about just 15 minutes of exercise a day?
Can boost life expectancy by three years and cut death risk by 14%.
What was the methods of the Wen et al (2011) study?
416,175 individuals
Average follow up duration 8.05yrs
Weekly exercise volume assessed using a self administered questionnaire
What were the results of the Wen et al (2011) study?
Compared with individuals in the inactive group, those in the low volume group who exercised for 15 min a day had a 14% reduced risk of all cause mortality and a 3 year longer life expectancy. Every additional 15 min of exercise beyond the minimum amount of 15 min a day further reduced all cause mortality by 4%.
Findings are the same for CVD, stroke, diabetes as for all cause mortality, but not quite as effective for cancers.
What has research suggested about death rate and sedentary time?
Age adjusted all-cause death rate increases as sedentary time increases.
Ekelund et al (2016) examined whether PA can protect against the ills of excessive sitting. What was the result?
Sitting time increased ACM risk in a dose-response fashion in all groups except the most active
No association between sitting time and ACM risk in the most active quartile.
ACM across sedentary quartiles was attenuated by increasing PA (60-75 min/d of PA eliminates the ACM risk associated with excessive sitting).
What did the aerobics centre longitudinal study about physical fitness and mortality show?
As fitness reduces, relative risk of premature mortality increases in men and women (dose-response).
Note: these risks for fitness are much stronger than risks seen for PA in other studies (fitness also takes account of genetic component).
A cohort study by Knoops et al (2004) examined Mediterranean diet, moderate alcohol use, PA and non-smoking, what did the results show?
Non-smoking reduces risk in all-causes and CVD but most reduced in cancers
Diet reduces risk in all but least in cancers
The combined impact of lifestyle factors
How can casual inference be gleaned?
by assessing
- Biological plausability
- Does-reponse
- Reversability
- Consitency of effect
- Appropriately sequenced
