The relationship between poor health and cognitive impairment is not fully understood yet. People with Down syndrome are prone to a number of health problems, including congenital heart defect, visual impairment, hearing loss, autoimmune diseases, epilepsy, early-onset Alzheimer's disease and intellectual disability. Our aim was to assess the impact of impaired health on cognitive performance in people with Down syndrome. A series of people with Down syndrome (n=129) were studied for their intellectual disability, sensory impairments and health concerns. The medical and psychological records of all persons with Down syndrome in the Intellectual Disability Service Register of Kainuu from 1970 to 2004 were analysed. The detected health issues were related to the individuals' cognitive levels. Visual impairment, poor dental health and acute neurological disease were associated with the severity of intellectual disability and ageing. (Contains 4 tables.)