Researchers conducted a cohort study among 400 participants, including both men

Question

Researchers conducted a cohort study among 400 participants, including both men and women, between the ages 40 and 64 to determine the effect of cigarette smoking on incidence of diabetes. To be eligible, participants had to be without any diagnosis of diabetes at baseline. Participants were enrolled at baseline and followed for 8 years, with follow-up assessments every 2 years (at years 2, 4, 6, and 8). At each assessment, participants reported their behaviors, including cigarette smoking, and asked to report any new diagnoses of diabetes. Of the 400 individuals, 4 reported a diagnosis of diabetes at the first assessment (2 years into the study), 6 reported a new diagnosis at the second assessment, 2 reported a diagnosis at the third assessment, and 7 reported a diagnosis at the fourth and final assessment. There were no losses to follow-up at the first assessment (2 years into the study), but 10 participants were lost to follow-up at the second assessment (4 years into the study), 12 participants lost to follow-up at the third assessment, and 5 participants lost to follow-up at the fourth and final assessment. What was the incidence rate (incidence density) of diabetes for the study? Select one: a. 6.25 cases of diabetes per 1,000 person-years b. 92.23 cases of diabetes per 1,000 person-years c. 47.5 cases of diabetes per 1,000 person-years d. 12.51 cases of diabetes per 1,000 person-years e. 8.47 cases of diabetes per 1,000 person-years

Explanation / Answer

Incidence rate or person time rate is a measure of incidence that incorporate time directly into the denomenator. Person time rate is generally calculated from long term cohort followup study, wherein enrolled are followed overtime and the occurance of new cases of disease is documented.

Incidence rate = no. Of new cases of disease/ time each person was observed, totalled of all person

To calculate denomenator, in our study for example follow up occur in every 2 year. Someone lost to followup in year 4 and someone diagnosed with disease in year 4 means each contribute 3.5 years of disease free followup to denomenator.

In this study

Total no of new cases of diabetes ( numerator) = 4+6+2+7 = 19

Denomenator person- year of observation

(4*1.5) +(6*3.5)+(2*5.5)+(7*7.5)+(0*0.5)+(10*2.5)+(12*4.5)+(5*6.5)+(354*8)

= 3034 person - year of observation

Total person have disease and lost follow up = 46 so 400-46= 354 . 354 person who were followed for 8 years and remain disease free.

Incidence rate = 19/3034

.00626 person- years of observation

.00626*1000 = 6.26 cases per 1000 person- years

So the answer is a).

Related Questions

Navigate

• Browse (All)
• Browse R
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.