. In a study concerned with the possible effects of air pollution on the development of chronic bronchitis,

the following data was obtained. A population of 9,000 men aged 45 years was examined in January 2010. Of these, 6,000 lived in areas where they were exposed to air pollution and 3,000 did not. At this examination, 90 cases of chronic bronchitis were discovered, 60 among those exposed to air pollution. All the men initially examined who did not have chronic bronchitis were available for subsequent repeated examination during the next 5 years. These examinations revealed 268 new cases of chronic bronchitis in the total group, with 3o among those unexposed to air pollution.

What is the prevalence proportion of chronic bronchitis in January 2010?

Prevalence:

/900

.01x100

% prevalence of chronic bronchitis in January 2010

What is the incidence rate (per 1,000) of chronic bronchitis for the 5 years among those exposed to air pollution?

Incidence: (268 new cases minus 30 that are unexposed to air pollution divided by 6000 people that are exposed to air pollution and minus 60 - the number of existing case at the beginning of the 5 year study)

=(268-30)/(6000-60)

/5940

.06 cases per 1,000 during 5 years

What is the incidence rate (per 1,000) of chronic bronchitis for the 5 years among those unexposed to air pollution?

What is the incidence rate (per 1,000) of chronic bronchitis for the 5 years in the total population?