Sundown syndrome: is it reflected in the use of PRN medications for nursing home residents?

Sundown syndrome describes the increase in agitation and delirium in elderly patients with dementia that occurs in the evening after sunset. In a nursing home, data were gathered over a year-long period to test the hypothesis that the administration of PRN (pro re nata, given as needed) medications for agitation in Alzheimer's patients would reflect sundown syndrome. More PRNs were administered in the early morning and mid-afternoon hours than at other times of the day. These outcomes suggest there is a relationship of PRN use for agitation, in institutionalized Alzheimer's patients, to environmental variables other than sunset.

A comparison of response patterns on fixed-, variable-, and random-ratio schedules.

The behavior of individual pigeons on fixed-ratio, variable-ratio, and random-ratio schedules was examined. Within each type of ratio schedule the size of the ratio was varied in an irregular sequence. At various ratio sizes (5, 10, 40, 80) no differences were found among overall response rates (postreinforcement pause plus running response rate) as a function of ratio type. This similarity in overall response rates held despite noticeable differences in the microstructure of performance both within and across subjects; the primary performance difference on the three types of ratio schedules was the relatively longer postreinforcement pause duration on the fixed-ratio schedule. We concluded that the gross temporal characteristics of performance determined by the relative weightings of the postreinforcement pause and running response rate were primarily controlled by the type of ratio schedule (fixed, variable, or random), whereas the overall rate of responding was controlled by the size of the ratio.