The sample size was calculated using estimating the exact proportion of the population, Then, perform Systematic Random Sampling the population was equal to 353 people in order to meet the specified number and the sample had equal opportunities. By sorting the elderly according to the list of Lak Hok Subdistrict Health Promoting Hospital, finding the ratio between the population and the sample. After that, a simple random drawing is done to find the starting members. From one member number 1-12, the next member's number is systematically assigned with the same distance between everyone. Continue doing this until there are 353 people.