|
Although
some individuals with TMD pain experience a single brief episode
of pain (e.g. following an injury), and some have pain every
day for years, the typical pattern of TMD pain is repeated episodes
lasting weeks or months, with pain on about half the days.
Point prevalence
assesses the presence of pain on the day of the interview. Thus,
a point prevalence measure might not capture significant pain
problems that are frequent or persistent, if they are not present
at the time of the survey.
For this reason,
period prevalence is probably the most appropriate type
of prevalence measure for TMD pain, and it is the most widely
used.
The best time
period for determining period prevalence is likely to vary with
aims of the study. If the subject is to be asked about non-trivial
pain, a period of 3 to 6 months generally is chosen, as this period
is long enough to capture recent cases, but not so long that it
taxes the subject's memory, and hence the quality of the data.
If a study
design calls for a follow up every 6 months, investigators might
choose to assess pain in the prior 6 months as the baseline measure,
so that baseline and follow up measures would cover equivalent
and non-overlapping time periods.
Cross sectional
studies sometimes collect multiple period prevalence measures
simultaneously (e.g. pain in the last week, in the last month,
in the last year).
|