Investigators conducted a study to investigate the association between pesticide exposure and dementia among migratory and seasonal agricultural workers. Using medical records from a California clinic that serves migrant and seasonal workers, individuals with dementia were selected based on cognitive screening tests performed on all patients. The comparison group was made up of individuals without dementia from the same clinic. Frequency and intensity of pesticide exposure was assessed using interviews about each individual's use of pesticides and personal protective equipment. Their results described the odds of pesticide exposure comparing those with and those without dementia. What type of study design was used