Question

Researchers are interested in the association between depression and average hours of sleep received each night among a group of participants in an observational study aged 25-40. Researchers collected information about sleep habits by observing sleep journals collected from participants and compiling average sleep over the study period into a variable based on tertiles of the average sleep for the whole study population. The outcome was assessed by means of responses on the geriatric depression scale (GDS). Suppose the following table compiles the study results. Calculate the relative risks for depression by amount of sleep by comparing each of the upper tertiles to the 1^st as the reference group.

	Depression (GDS>19)	Depression (GDS≤19)	Total
1st Tertile of Sleep	41	196	237
2nd Tertile of Sleep	56	181	237
3rd Tertile of Sleep	111	126	237
Total	208	503	711

Choose the most appropriate option

		Option A RR1 (1st to 2nd)=0.37, RR2 (1st to 3rd)=0.42
		Option B RR1 (1st to 2nd)=0.65, RR2 (1st to 3rd)=0.35
		Option C RR1 (1st to 2nd)=0.42, RR2 (1st to 3rd)=0.44
		Option D RR1 (1st to 2nd)=0.73, RR2 (1st to 3rd)=0.24

Answer 1

Cumulative Incidence for Depression (GDS>19) for 1st Tertile of Sleep, CI1 = 41/237

Cumulative Incidence for Depression (GDS>19) for 2nd Tertile of Sleep, CI2 = 56/237

RR1 (1st to 2nd)= CI1 / CI2 = (41 / 237) / (56 / 237) = 41/56 = 0.73

Cumulative Incidence for Depression (GDS>19) for 3rd Tertile of Sleep, CI2 = 111/237

RR1 (1st to 3rd) = CI1 / CI3 = (41 / 237) / (111 / 237) = 41/111 = 0.37

The answer is

RR1 (1st to 2nd)=0.73, RR2 (1st to 3rd)=0.37

None of the given options are correct. Please check if the all the options are given