Table 3.

Key studies examining multiple medicines used in populations with intellectual disability (ID).

Title, year, country	Aim	Setting, population, sample size	Definition of multiple medicine use	Results
Factors associated with polypharmacy and excessive polypharmacy in older people differ from the general population: a cross-sectional study9 O’Dwyer et al.(2016), Ireland	To determine the prevalence of polypharmacy and excessive polypharmacy in older adults with ID and the clinical and demographic factors associated with polypharmacy and excessive polypharmacy	Cross-sectional study of 736 older adults (41–90 years) with ID from wave 1 (2009/2010) of IDS-TILDA, a nationally representative study of older adults with ID in Ireland	Polypharmacy was defined as 5–9 medicines. Excessive polypharmacy was defined as 10 or more medicines	Polypharmacy was observed in 31.5% of participants and excessive polypharmacy in 20.1%. Living in an institutional setting, reporting a mental health condition or neurological condition were significantly associated with polypharmacy and excessive polypharmacy after adjusting for confounders, but age or sex had no significant effect
Prevalence and factors associated with polypharmacy in Victorian adults with intellectual disability60 Haider et al. (2014), Australia	To describe the prevalence of medicine use and polypharmacy (defined as five or more concomitant medicines), and to investigate the factors associated with polypharmacy in a population of people with ID	897 adults aged 18–82 years (mean age 42 years), with all levels of ID (74% had mild or moderate ID). Participants drawn randomly from the Victorian Population Survey of People with ID. This study contained participants from an administrative database of people with ID who had sought assistance from the Victorian Department of Human Services	Concomitant use of 5 or more medicines	In the population, 76% used medicines, and 21% were exposed to polypharmacy. At multivariate analysis, polypharmacy was associated with older age, unemployment, increased health checks and general practitioner (GP) visits. Those with epilepsy, diabetes, stroke, cancer and osteoporosis had more polypharmacy
Title, year, country	Aim	Setting, Population, Sample Size	Definition of multiple medicine use	Results
Atlas on the Primary Care of Adults with Developmental Disabilities in Ontario61 Lunsky et al. (2013), Canada Canada	To explore prevalence and patterns of medication use, with emphasis on those with multiple medicines (defined as two or more) in adults with ID	52,404 adults with ID aged 18–64 years who were receiving income support from the Ontario Disability Support Program, and were eligible to have medications paid for under the Ontario Drug Benefit Program	Patterns and number of medicines used on a given date in 2009 (from pharmacy claims data) Multiple medicines classed as 2 or more, also used threshold of 5 or more dispensed medicines	Of the sample, 26% were dispensed 2–4 medicines, and 21.5% had 5 or more medicines. 39.5% had no medicines dispensed. Antipsychotics (21.1%), benzodiazepines (13.1%) and SSRI antidepressants were most commonly dispensed. The number of medicines increased with age and among those with high morbidity levels and was higher among women (univariate). Those with a psychiatric diagnosis had a greater prevalence of multiple medicine us compared with those with no psychiatric diagnosis
Medication use among Australian adults with intellectual disability in primary healthcare settings: a cross-sectional study62 Doan et al. (2013), Australia	To investigate the extent of medication use in Australian adults with ID living in the community and accessing generic primary health care, and to explore associations between demographic and medical variables and psychotropic medication use	117 adults with ID living in the community in Brisbane (mean age 35 years), all levels of ID. Derived from a larger randomized controlled trial: the Advocacy and Health Study	Numbers, and classes of medicines and supplements taken. Medication data reported by person with ID or carer, health assessment carried out by general practitioner	Of the 117 participants, 79% reported currently taking medicines, a median of 3 medicines. Psychotropics were most frequently reported by 35%, followed by anticonvulsants (26%), and analgesics and gastrointestinal medicines (25%). Having a psychiatric illness or challenging behaviours were significantly associated with increased odds of using psychotropics
Title, year, country	Aim	Study Population, Sample Size	Definition of multiple medicine use	Results
The documentation of health problems in relation to prescribed medication in people with profound intellectual and multiple disabilities63 Van der Heide et al. (2009), The Netherlands	To document if there was an associated health problem documented in the notes for frequently prescribed medicines among people with profound intellectual and multiple disabilities	254 adults from 8 residential settings (46% male, 54% female). All had profound intellectual and multiple disabilities, an estimated intelligence quotient of 25, and profound or severe motor disorders	Medication use was defined as a prescribed medication in the previous year, use of 5 or more prescribed medications in the previous year was also analysed (medication and health data from pharmacy and case records)	Of the 254 participants, 89% were prescribed 1 or more medicines over the course of 1 year, and 40% were prescribed 5 or more medicines. Overall 92% had a documented reason for medicines use. Most frequently reported classes were laxatives (65%), anticonvulsants (56%), and drugs for peptic ulcer and gastro-oesophageal reflux disease (52%)
Health problems of people with intellectual disabilities: the impact for general practice28 Straetmans et al. (2007), The Netherlands	To analyse health problems and prescription patterns of people with intellectual disabilities registered with GPs, and the differences in health problems between people with intellectual disabilities and controls (without intellectual disabilities)	868 individuals with ID, and 4305 controls (people without ID). Each individual with ID was matched to 5 people without ID with regard to age, sex and practice. Individuals came from 87 GP practices.	Numbers of acute and repeat prescriptions. All therapeutic classes analysed	People with intellectual disabilities paid 1.7 times more visits to GPs and received four times as many repeat prescriptions. Psycholeptics, anticonvulsants and psychoanaleptics were the most frequently reported repeat prescriptions for people with ID. Different morbidity patterns

SSRI, selective serotonin reuptake inhibitor.