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Temporomandibular Disorders
Author Bios
Introduction
Epidemiology
Currently selected section: Population Perspective
Developmental Perspective
Ecological Perspective
Epidemiologic Measures
Defining a Case
Pain Location
Pain Frequency, Duration and Severity
Recency of Pain
Ambient Pain or Pain on Function?
Clinical Signs and Symptoms
Pain Impact/Disability
Co-morbidity
Choosing an Appropriate Design
Cross-sectional Surveys
Longitudinal Studies
Case-control Studies
Currently selected section: Prospective Designs
Preventive and Clinical Trials
Clinical Epidemiology
Practical Considerations
Sample Size
Standardizing Data Collection
Response Burden
Summary

 

Chapter 26: Studying the Epidemiology of Temporomanibular Disorders: Prospective Designs
          

A prospective study is a longitudinal study that starts with persons not affected by the condition of interest in order to study risk factors. Alternatively, a cohort of persons in the early stages of illness may be identified if the goal is to study risk factors for chronicity. These cohorts are then followed over time to identify onsets of the condition, or other endpoints of interest (e.g. recurrence of the condition, chronicity, or disability).

A true prospective design requires frequent surveillance of the subjects to detect endpoints occurring over the follow up period, and reasonably precise dating of the occurrence of the endpoint.

Stratifying the cohorts by risk factor status at the outset, or as the study progresses, allows for inference about the relationship of the risk factor to the risk of subsequent occurrence of the endpoint.

A retrospective (also referred to as non-concurrent or historical) cohort study uses historical records of exposure to a risk factor and subsequent disease experience to investigate the relationship of a risk factor to disease occurrence. For example, records documenting the distance survivors were from the hypocenter of the atom bomb explosion in Hiroshima were used to study the effect of different levels of radiation exposure on the incidence of leukemia and the period from exposure to onset of disease (Cobb et al., 1959).

Example
Von Korff et al. (1993) used a prospective design to determine whether elevated levels of depressive symptoms placed individuals at risk of first onset of TMD pain, back pain, headache, abdominal pain or chest pain. They followed up a sample of 803 persons initially interviewed in a pain prevalence survey. At a three year follow-up, they found that persons with elevated levels of depressive symptoms at baseline were more likely to report first onset of headache and chest pain at follow-up, but were not at increased risk of first onset of TMD pain, back pain, or abdominal pain. For chest pain and headache, first onset rates were highest among the chronically depressed. The risk of experiencing a first onset of TMD was higher among persons who experienced other pain conditions at baseline. As the number of pain conditions at baseline rose, the probability of developing TMD pain increased. Similar relationships were found for the other pain conditions as well.

 

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