Survey data from different populations suggests that the overall prevalence of congestive heart failure in persons 75 years of age and older is about 9-10%.

Three different surveys in the literature report the prevalence of CHF. Two were rural counties in Vermont and North Carolina; the third was from an urban setting in Minnesota. As you can see, the prevalence rate increases with age, and for individuals at or over the age of 75 the prevalence rate is quite high - about 10%.

REMINDER:
The prevalence of something is the number of instances of a given disease or other condition in a given population at a designated time; sometimes used to mean prevalence rate. When used without quantification, the term usually refers to the situation at a specified point in time (point prevalence).

The prevalence rate is the total number of all individuals who have an attribute or disease at a particular time (or during a particular period) divided by the population at risk of having the attribute or disease at this point in time or midway through the period.

So, if you wanted to know the prevalence rate of congestive heart failure in your sample, what would you have to do? First pick a time period, say one week. Then, count all the individuals with a diagnosis of congestive heart failure. Then, divide by the population at risk for congestive heart failure, and multiply by 100 to get the prevalence rate in percent form.