Chronic disease epidemiology

What is chronic disease epidemiology?

It is a way of investigating a link between dietary behaviour and chronic diseases.

Epidemiological studies used:

* 24 hours recall
* Diet history
* Food frequency questionnaire

Types of chronic disease:

* type 2 diabetes
* Heart disease
* Stroke

Ways to investigate the link between dietary behaviour and chronic diseases

* Anthropometric
 Using body weight, height, skin folds, waist and hip circumference

* Biochemical tests

Blood, urine, faeces, tissues are rested to deter subclinical deficiencies

* Clinical observation

Observation of pallor,  hair, nails, skin, eyes, lips, mouth , muscles, joints

* Dietary assessment

Obtain report of food items consumed, portion sizes, frequency, calculation of nutritional intake

Stages of change model

The stages of change model is often used in nutrition and dietetics.

What does Stages of Change model mean?

It begins with building a solid foundation of recovery.

There are 5 steps:

1.  Pre contemplation

This is where the patient is not actively looking for change.  Perhaps they were not aware of needing a change or have no desire to change.

2.  Contemplation

The patient is beginning to wonder if there may be an issue needs addressing.  Is there  a problem here or not?

3.  Preparation

A plan is being developed to address the problem.

4.  Action

New behaviours are beginning to be implemented to address the problem.  This typically lasts 3-6 months.

5.  Maintenance

Symptom free behaviour continuing the good work!

Confounding factors

Within nutrition, confounding factors play a large part in trials.

The relationship between disease and exposure can experience confounding.  IE Alcohol drinkers.  Do they suffer more heart disease than non alcohol drinkers?
As smoking is often associated with alcohol consumption, is it possible that alcohol drinkers may have more heart disease but due to smoking as opposed to drinking alcohol?  This would be confounding.

Therefore, the relationship between alcohol and heart disease could be due to some confounding variable.

RCTs - Randomised control trials

Placebos are used in randomised control trials to limit the potential for any bias.

Blind controls as used in cases where subjects do not know if they belong to the placebo group or not.

Double blind controls happen where neither the subject being tested or the investigators are aware wh his in the placebo group.

Case control and cohort studies

What are case control studies and cohort studies?

What does this mean in clinical nutrition?

Case control studies are observational studies in which two existing groups (differing in outcome) are identified and compared on the basis of a casual attribute.

Group 1 - Has the condition or disease plus another factor.
Group 2 - Does not have the disease but has the same factor.

Cohort studies uses a group of people who share a common defining characteristic such as graduation or birth etc.
An analysis over time of risk factors of people who do not have a disease but uses correlations to determine the absolute risk.

What is Scientific bias?

Scientific bias is a systematic error.  It gives an association that is not true.

In nutrition there are 5 main types of bias which can be found within studies:

Measurement bias - Poorly measured or improperly measured tests. Such as machines not been correctly calibrated for example.

Interviewer Bias - The outcome of the results is shaped by the belief of the interviewer.  For example, should the interviewer feel there would be a benefit from the test, they will impress upon the subject their own bias.

Selection bias - Proper randomisation of subjects is not achieved.

Social acceptability bias - Survey respondents will answer questions in a manner which will be viewed favourably by others.  Some people change their habits to encourage a better view of themselves.  If there was an exercise questionnaire,  subjects may be inclined to increase their exercise for better opinions of themselves.

Recall bias - Inaccurate recollections by study participants.  It is not always easy to remember.  IF subjects were asked to write down what the had eaten earlier in the day, they might well not remember.

Bias Mind map.

Epidemiology and exam help

Epidemiology - this is the one I felt would be common sense. I felt this would be simple and straight forward.

No.

Not so.

Yikes.

To help me revise (no, hang on, to learn) I am going to try writing blog posts.  Pray to God this will help you guys too.  Let me know if it helps any of you...so, ok, here we go.

Epidemiology is 'the study of the occurrence and distribution of health related events, stats and processed in specified populations, including the study of determinates influencing such precesses and the application of this knowledge to control relevant health problems.' (Porto M. A dictionary of Epidemiology)

Distribution means the frequency and pattern of health events in a population.
Population is a group of people with a common characteristic.
Determinants are factors or events that influence health.

Epidemiology is a tool used by governments to determine investigations into public health.

Common terms used are

Sporadic - a disease which occurs occasionally and often irregularly
Endemic - Constant presence of disease within a given population.
Epidemic - above the expected level of occurrence of disease
Pandemic - an epidemic weidspread over several countries or continents.

Morbidity: any departure from a state of physiological or physiological well being.
Mortality: a number of reported deaths in a population in a specific time period.

Analytical Epidemiology - Basic question - "Is exposure and disease linked?"

Research questions/hypothesis - Do persons with exposure have higher levels of disease than persons without exposure?

3 major factors in epidemiology:
social factors
lifestyle factors
personal characteristics

Measure of disease frequency: Incidence = number of new cases of disease the developed during a specified period of time.
Prevalence - number of existing cases of disease at a given point of time or during a period of time.

I hope some of this may have helped, the next few blog posts go into specifics of exam questions you may find help you to revise! Good luck.