You are the epidemiology consultant to a cotton fabric manufacturer. Because of

Question

You are the epidemiology consultant to a cotton fabric manufacturer. Because of some suspicion on the part of local physicians, you conduct a study of the occurrence of respiratory disease among the workers and obtain the following results:

Incidence of respiratory disease among workers exposed to the cotton fiber = 200 per 100,000 per year

Incidence of respiratory disease among workers not exposed to the cotton fiber = 40 per 100,000 per year

Incidence of respiratory disease among general population = 45 per 100,000 per year

1a. Calculate and interpret the rate ratio (RR).

1b. Calculate and interpret the attributable rate (AR).

1c. Calculate and interpret the population attributable rate percent (PAR%)?

1d. Labor asks you to estimate how many people in their factory of 25,000 workers develop respiratory disease per year as a result of cotton fiber exposure.

Explanation / Answer

1.a Rate Ratio = (IRe) / (IRIu)

the ratio of incidence rates in the exposed and unexposed groups.

rate ratio = 200/40 = 5

1.b   Attributable Risk (AR) is the difference in the disease rates in exposed and unexposed individuals.

AR = IRe - IRu = (200-40) / 100,000 = 160 per 100,000

1.c   PAR = risk incidence in population – risk incidence in non-exposed = (45 - 40) = 5 per 100,000

PAR% = (PAR / risk incidence in population)*100 = (5/45)*100 = 11.11%

1.d   Incidence of respiratory disease among workers exposed to the cotton fiber = 200 per 100,000 per year

so in 25,000 workers (200/100,000)*25000 = 50 workers will be having respiratory diesese due to cotton fibre exposure

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