Table 1.
Characteristics of studies reporting mortality rates for respiratory disorders and pneumonia in people with intellectual disabilities (ID)
| Author | Country | Study design, setting and follow-up | Data sources | ID sample (n, % female, age, level of ID) | Deaths in ID sample (n, % female, age at time of death, level of ID) | Comparison sample (n, % female, age) and deaths (n, % female, age) | Respiratory disorder definition (eg, ICD codes or other definitions) | Quality percentage (assessment) |
| Brameld et al (2018)26 | Australia | Retrospective matched cohort study of adults 20 years old and over. Follow-up 2009–2013 | Intellectual Disability Exploring Answers (IDEA) Database. Death certificate data | Total sample characteristics not available | n=591; 43.8% female; mean age* and level of ID not available | Total sample characteristics not available. Number of deaths=62 917; 47.4% female; mean age not available | ICD 10-chapter codes for respiratory disorders | 95.45% (strong) |
| Cooper et al (2020)28 | UK | Population-based cohort study. Follow-up 2001–2018 | Primary care records and health check data; death certificate data. Comparison data from Health Board statistics | n=962; 45.4% female; mean age=44.1 years (range 16–83); ID mild=382 (39.7%), moderate=236 (24.5%), severe=180 (18.7%), profound=163 (17.0%) | n=294/961 (30.6%); 47.5% female; mean age=52.4 (SD 13.6) | Not available | ICD 10-chapter codes for respiratory disorders | 86.36% (strong) |
| Dupont et al (1987)43 | Denmark | Population-based cohort study of adults with mild ID. Follow-up 1976–1984 | Danish National Service for the Mentally Retarded. Death certificate data | n=7134; gender, age and level of ID not available | n=446; 37.9% females; age and level of ID not available | Not available | Not described | 40.90% (weak) |
| Durvasula et al (2002)30 | Australia | Population-based cohort study of children and adults. Follow-up 1989–1999 | ID prevalence study. Death certificate data, medical records and postmortem data. Australian Bureau of Statistics | n=693; 44.6% female; mean age=N/A; ID 40% mild, 35% moderate, 25% severe/profound | n=40 (6%); 45% female; median age=32 (range 10–59); level of ID not available | n=1 25 848; 51% female; mean age not available. Number of deaths=2154; 37.8% female; mean age not available | Not described | 90.91% (strong) |
| Forsgren et al (1996)15 | Sweden | Population-based cohort study of adults with ID. Follow-up 1986–1992 | Board for Provision and Services to the Mentally Retarded. Death certificate data from Swedish National Bureau of Statistics | n=1478; 44.5% female; age and level of ID not available | n=247; 42.1% female; median age=64 years (IQR 52–75 years); ID 39.7% mild, 31.2% moderate, 21.5% severe, 7.7% profound | Not available | ICD 9-chapter codes for respiratory disorders | 81.82% (strong) |
| Glover et al (2017)8 | UK | Population-based case–control study in primary care. Follow-up 2010–2014 | Primary care records (Clinical Practice Research Data, CPRD). Death certificate data | Total sample characteristics not available | n=664 deaths; 44.1% female | Total sample characteristics not available. Number of deaths=97 379; 52.3% female; mean age not available | ICD 10-chapter codes for respiratory disorders | 81.82% (strong) |
| Heslop et al (2014)5 | UK | Population-based audit of deaths of children and adults with ID aged 4 and over. Audit period 2010–2012 | Medical records. Death certificate data from UK Office of National Statistics | Total sample characteristics not available | n=247; 42.1% female; median age=64 years (IQR 52–75 years); ID 39.7% mild, 31.2% moderate, 21.5% severe, 7.7% profound | Total sample characteristics not available. Number of deaths=480 467; 51.6% female; median age not available | 81.82% (strong) | |
| Hollins et al (1998)11 | UK | Cohort study of adults on an ID register. Follow-up 1982–1990 | Learning disability register. Death certificate data. | n=2026; gender, age and ID level not available | n=268 deaths; gender and age not available; 51.5% mild–moderate, 48.5% severe–profound | Not available | Not described | 81.82% (strong) |
| Hosking et al (2016)24 | UK | Population-based case–control study in primary care. Follow-up 2009–2013 | Primary care records (CPRD linkage). Death certificate data | n=16 666; 58.1% female; mean age 39.9 (SD: 16.2). 19.6% of sample had high support needs | n=656 (3.9%); 55.6% female; age and level of ID not available | n=113 562; 58.1% female; mean age not available. Number of deaths=1358 (1.2%); 60.4% female; mean age not available | ICD 10-chapter codes for respiratory disorders | 90.91% (strong) |
| Janicki et al (1999)22 | USA | Cohort of adults with ID 40 years old and over. Follow-up 1984–1993 | Data from state agency with responsibility for reviewing deaths of disabled persons. Health department data | Total sample characteristics not available | n=2752, 48.1% female; mean age- 65.1; ID 18%, 68% Moderate–profound, 4% unspecified, 10% unknown | Total sample characteristics not available. Number of deaths=149, 980; gender not available, mean age=70.0 | ICD 9-chapter codes for respiratory disorders | 77.27% (strong) |
| Ng et al (2017)12 | Sweden | Population-based case–control study of adults with ID 55 years old and over. Follow-up 2002–2015 | National database of hospital admissions and outpatient care. National disability register. Swedish National Cause of Death register | n=15 289; 45.5% females; mean age not available; level of ID not available | n=4728; 44.9% female; age and ID level not available | n=74 445; 45.5% females; mean age not available. Number of deaths=8364 | ICD 10-chapter codes for respiratory disorders | 95.45% (strong) |
| Oppewal et al (2018)27 | Netherlands | Cohort study of adults with ID 50 years old and over living in three care organisations. Follow-up November 2013–March 2018 | Medical case notes of participants with ID who died during study period. Cause specific mortality statistics for 50+ population in the Netherlands | n=1050; 48.7% female; mean age=61.6 (SD: 8.0, range 50–94); ID level=2.9% borderline, 21.2% mild, 48.2% moderate, 16.4% severe, 8.7% profound | n=207 deaths (19.7%) but only 159 with cause of death available. 60.7% female; mean age not available; ID level=5.7% borderline, 18.9% mild, 54.7% moderate, 13.2% severe, 7.5% profound | Not available | ICD 10-chapter codes for respiratory disorders | 50.0% (weak) |
| Patja et al (2001)14 | Finland | Population-based, nationwide cohort study. Follow-up 1963–1997 | Original 1962 population-based study (Amnell et al 1964). Death certificate data | n=2369, gender, age and level of ID not available | 1111 deaths with death certificates available for 1095–51.0% female, mean age=57.7; ID 40.3% mild, 29.4% moderate, 11.5% severe, 18.0% profound, 0.7% unknown | Not available | ICD 9-chapter codes for respiratory disorders | 81.82% (strong) |
| Raitasuo et al (1997)13 | Finland | Cohort study of adults living in an institution. Follow-up 1972–1993 | Medical case notes and death certificate data. General population mortality statistics for population in Finland | N ≈ 2000; gender, age and level of ID not available | 216 deaths, 42.6% female; mean age 26.7 (1–86 years); ID level 2.0% borderline, 15.0% mild, 18.0% moderate, 20.0% severe, 45.0% profound, 20.0% unknown | Not available | ICD 9-chapter codes for respiratory disorders | 54.55% (weak) |
| Smith et al (2020)10 | UK | Nationwide, population-based cohort study of children aged 4–19. Follow-up 2008–2015 | Scottish pupils census: death certificates data | n=18 278; 35% female; mean age not available | n=106; mean age=14.3 (95% CI: 13.4 to 15.1); level of ID not available | n=7 77 912; 50% female; mean age not available. number of deaths=458; mean age=16.1 years (95% CI: 15.8 to 16.5) | ICD 10-chapter codes for respiratory disorders | 100% (strong) |
| Trollor et al (2017)25 | Australia | Population-based cohort study of adults 20 years old and above registered with disability services. Follow-up 2005–2011 | Disability Services Minimal Data set. Australian Bureau of Statistics. Death records | n=19 362; 44% female, mean age=37 (range 27–48); ID not available | n=732 (4%); 41% female; median age=54 (42–64), level of ID not available | Total sample characteristics not available. Number of deaths=305 050; 49% female; median age=81 (70–92). | ICD 10-chapter codes for respiratory disorders | 95.45% (strong) |
| Tyrer and McGrother (2009)23 | UK | Population-based cohort study of individuals with moderate- profound ID on a register. Follow-up 1993–2006 | Leicestershire learning disability register. Death certificate data. National Statistics 1993–2006 | n=2995; 41.9% female; Age and level of ID not available | n=503; gender, age and level of ID not available | Total sample characteristics not available. Number of deaths≈126 000 | ICD 9 and ICD 10-chapter codes for respiratory disorders | 72.73% (moderate) |
*Individuals in the ID cohort died at a significantly younger age than the comparison cohort.
ICD, International Classification of Diseases; ID, intellectual disabilities; N/A, not available.