4) Authors of a recent article in the Journal of the American Medical Associatio

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4) Authors of a recent article in the Journal of the American Medical Association conclude based on their study that participation in physical activity within 1 week after a concussion may benefit symptom recovery following a concussion in children and adolescents. The authors followed a sample of participants who had a concussion and determined l) 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 day7 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%l, sport-specific exercise (n 214 18.9%D, noncontact drills (n l43[5.9%D, full-contact practice physical activity". Early physical activity participants had lower risk of PPCS than those Given this information and assuming the 2413 participants are a random sample of children and adolescents who had a concussion: 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 asample including these 869 participants and the 2413participants represent a random sample of children and adolescents who had a concussion? Why or why not h Suppose the l172 participants and the 869 participants all performed early physical activity and also all had PPCS at day28? Then, based on the total sample of 4454

Explanation / Answer

Please find the table for 2413 participants:

a) Number of participants who did not have PPCS on Day 28 = 415.84 + 1264.46 = 1680 (Answer)

b) No of participants who performed early physical activity and had PPCS on day 28 = 412 (Answer)

c) Risk difference for PPCS = 43.5%-24.6% = 18.9%

d) Relative risk for PPCS = 43.5/24.6 = 1.77

e) One reason for disagreement can be that the sample size for people who do physical activity and dont do it is not the same. Also, there is no information about the proportion of children and adoloscents in each sampel

f) 2413 does not represent a random sample

g) Inclusion of 869 participants will not represent a random sample because 1172 patients did not participate and there is no information about their reason for not participating . Also, there is no information about comparison of profile of these 1172 patients and the rest of the participants.

h) Suppose 4454 is the sample size, above table will look like the following

Risk difference for PPCS for participants with early physical activity vis-a-vis no physical activity = 22.49%

Relative risk for PPCS = 43.5/65.99 = .66

Evaluation on Day 7 Evaluation on Day 28 No participation in early physical activity Number %age Number %age 736 30.50145 PPCS 320.16 43.5 Non PPCS 415.84 56.5 Total 736 100 Participation in early physical activity Light aerobic exercise 795 32.94654 Sport specific exercise 214 8.868628 Non contact drills 143 5.926233 Full contact practice 106 4.392872 Full competition 419 17.36428 Total 1677 69.49855 PPCS 412.542 24.6 Non PPCS 1264.458 75.4 Total 1677 100 Grand Total 2413 100

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