The authors followed a sample of participants who had a concussion and determine

Question

The authors followed a sample of participants who had a concussion and determined 1) whether they participated in early physical activity (physical activity within 7 days after the concussion, and 2) whether they had PPCS, persistent post-concussive symptoms as measured on day 28 (28 days from the concussion). In the abstract, the authors state that among 2413 study participants who were evaluated for physical activity at day 7 and for PPCS at day 28, “PPCS at 28 days occurred in 733 (30.4%); 1677 (69.5%) participated in early physical activity including light aerobic exercise (n=795 [32.9%]), sport-specific exercise (n=214 [8.9%]), noncontact drills (n=143[5.9%]), full-contact practice (n=106[4.4%]), or full competition (n=419 [17.4%]), whereas 736 (30.5%) had no early physical activity”.

   .   a) How many participants did not have PPCS at day 28?

   .   b) How many participants performed early physical activity and had PPCS at day 28?

   .   c) What is the risk difference for PPCS comparing participants with early physical activity
to participants without early physical activity?

   .   d) [*1 pt] What is the relative risk for PPCS comparing participants with early physical
activity to participants without early physical activity?

   .   e) Provide at least one reason why one might disagree or be concerned with the author’s
conclusion?

There were actually 4454 children and adolescents who were eligible for the authors’ study but 1172 did not consent and 869 were excluded from the analysis for various reasons (including missing information about physical activity within 7 days or PPCS at day 28).

   .   f) Given this additional information, do the 2413 participants represent a random sample?

   .   g) Suppose the 869 participants were NOT excluded, and information about their physical
activity within 7 days or PPCS at day 28 were known. Would a sample including these 869 participants and the 2413 participants represent a random sample of children and adolescents who had a concussion? Why or why not?

   .   h) Suppose the 1172 participants and the 869 participants all performed early physical activity and also all had PPCS at day 28? Then, based on the total sample of 4454

children, what is the risk difference and the relative risk, comparing participants with early physical activity to participants without early physical activity?

Explanation / Answer

Answer:

Total study participants 2413

Total study participants (2413)

1677, 69.5% (involved in physical activity after 7days)

733, 30.4% (PPCS after 28days)

736, 30.5% (no physical activity after 7days)

1680, 69.6% (no PPCS after 28days)

Total study participants (2413)

1677, 69.5% (involved in physical activity after 7days)

733, 30.4% (PPCS after 28days)

736, 30.5% (no physical activity after 7days)

1680, 69.6% (no PPCS after 28days)

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