Aging with a Developmental Disability in Ontario: A Guide for Families

If you’re supporting an adult with a developmental disability in Ontario, one of the most important things to understand is that later life often arrives sooner than you’d expect. Aging can begin in the 40s rather than the 60s, and for some people — especially those with Down syndrome — it brings health changes that mainstream seniors’ services aren’t built to catch. This guide explains what “aging” really means for this population, why establishing an early baseline matters so much, how dementia can look different here, and how to plan ahead across a system that splits responsibility between two ministries — in plain language, with every figure sourced and dated.

The short version

• Adults with developmental disabilities age earlier and faster than the general population. In Ontario, signs of frailty appear in adults with developmental disabilities as early as age 40 — a level (roughly 8%) not reached until after age 75 in adults without developmental disabilities (H-CARDD/ICES, 2014) — so “later life” planning should begin in the 40s, not the 60s.
• Down syndrome carries a near-universal, genetically driven risk of Alzheimer’s disease. Amyloid plaques are present in virtually everyone with Down syndrome by age 40; the lifetime risk of dementia exceeds 90%; and dementia presents at a mean age of onset of 53.8 years (with prodromal changes around 50.8 years) — roughly 20 years earlier than the general population (Fortea et al., Lancet 2020; Lancet Neurology 2021).
• Dementia looks different in this population. Early changes are often behavioural, personality, and executive-function changes (and new-onset seizures) rather than the memory loss seen first in the general population — which is why establishing an early cognitive/functional “baseline” is essential.
• Other age-related changes cluster and arrive early: vision and hearing loss, osteoporosis and fractures, earlier menopause, multimorbidity, and polypharmacy. These are treatable and often missed.
• The systems built to serve aging adults don’t fit this population well. In Ontario, responsibility is split between MCCSS (developmental services) and the Ministry of Health / Ontario Health (seniors’ and long-term care). Good later-life support means baselining, health monitoring, adapting pace and environment, planning end-of-life care early, and bridging the developmental-services and seniors’-services silos.

What every family should know

1. Premature and accelerated aging is real and measurable. Ontario administrative data show frailty appearing about 35 years earlier in adults with developmental disabilities than in those without. Practically, “aging” services and monitoring should begin at 40 — and for people with Down syndrome, even earlier.
2. Down syndrome and Alzheimer’s disease is the single most important later-life health issue (and is covered in the most depth below). The association is genetic (triplication of the APP gene on chromosome 21), the neuropathology is near-universal by 40, and dementia is now the leading cause of death in adults with Down syndrome over 35.
3. Baselining is the central practical tool. Because everyone starts from a different cognitive and functional baseline, detecting decline requires knowing the individual’s prior level of functioning. Screening tools designed for this population (NTG-EDSD, DSQIID) are built around detecting change from baseline, not absolute scores.
4. Diagnostic overshadowing — attributing new symptoms to the pre-existing disability rather than a new illness — is a named risk that can cause real illness (including dementia) to be missed. See Dual Diagnosis and Diagnostic Overshadowing in Ontario: A Family Guide to Mental Health and Developmental Disability.
5. Care transitions are poorly served by mainstream seniors’ services. Long-term care homes and generic seniors’ day programs are frequently a poor fit. Emerging best practice favours “aging in place” with dementia-capable adaptation of familiar environments.
6. Palliative and end-of-life care is under-accessed. People with intellectual and developmental disabilities are referred to specialist palliative care less, are identified for end-of-life care later, and receive less symptom relief than the general population.
7. The jurisdictional gap is structural. Developmental-services and health/seniors systems each tend to assume the other “owns” aging adults with developmental disabilities, leaving families to navigate the seam.

Aging comes earlier — and faster

Adults with intellectual and developmental disabilities are living far longer than in previous generations. For Down syndrome specifically, the GLOBAL Medical Care Guidelines note that average life expectancy increased from 25 years in 1983 to 60 years in 2020 (Tsou et al., JAMA, 2020). But longer life comes with many age-related changes arriving earlier. The clinical literature describes this as “accelerated” and, in some conditions, “segmental” or “atypical” aging: some but not all body systems age prematurely.

Ontario-specific evidence (H-CARDD/ICES). In the H-CARDD “Aging Profiles of Adults With and Without Developmental Disabilities in Ontario” report (Ouellette-Kuntz & Martin, 2014), using a cohort of 51,138 Ontario adults with developmental disabilities linked at ICES:

• Frailty (Johns Hopkins Frailty Marker) affected 8.9% of adults with developmental disabilities versus 3.1% of those without.
• Frailty appeared as early as age 40 in adults with developmental disabilities at a level of approximately 8% — a proportion not reached until after age 75 among adults without developmental disabilities — roughly a 35-year gap (consistent with reported life-expectancy and age-at-death gaps in Europe and Australia).
• Adults with developmental disabilities were far more likely to have used home care (about 12.5% vs 3.6%) and long-term care (about 11.6% vs 1.4%) despite being, on average, a younger population.
• By 2021, the number of adults with developmental disabilities over age 64 was projected to be over 1.6 times the 2009/10 figure — a demographic wave that services must plan for.

Which populations show accelerated aging, and why.

• Down syndrome is the clearest example, with dementia, early sensory decline, earlier menopause, and immune/endocrine changes; biological aging biomarkers (immunosenescence, “inflammaging”) support a progeroid pattern.
• Cerebral palsy shows premature musculoskeletal and functional decline and emerging evidence of elevated dementia/mild-cognitive-impairment risk at younger ages.
• More broadly, adults with intellectual disability face earlier onset of chronic conditions and functional limitation; a 2025 analysis (Healthcare/MDPI) found that on average a 44-year-old with a developmental disability had a level of functional limitation far exceeding chronological-age expectations, concluding that care should be function-based rather than age-based.

What this means in practice. “Later life” for this population effectively begins in the 40s. Aging-related health monitoring, baselining, and support-planning conversations should start earlier than for the general population.

Down syndrome and Alzheimer’s disease

This is the single most important later-life health topic for many families, so it’s worth taking slowly.

The genetic association. Down syndrome results from trisomy 21. Chromosome 21 carries the amyloid precursor protein (APP) gene; having three copies causes lifelong overproduction of amyloid-beta, which accumulates as the plaques characteristic of Alzheimer’s disease. Down syndrome is now understood as a genetically determined form of Alzheimer’s disease, analogous to autosomal-dominant Alzheimer’s (Fortea et al., Lancet Neurology 2021).

Near-universal neuropathology by age 40. Amyloid plaques and neurofibrillary tau tangles sufficient for a neuropathological diagnosis of Alzheimer’s are present in virtually all adults with Down syndrome by age 40 (Fortea et al., Lancet Neurology 2021; GLOBAL/JAMA 2020 guideline). Intraneuronal amyloid accumulation begins in the first decade of life.

But pathology precedes symptoms by 10 or more years. There is a long prodromal/preclinical phase: pathology accumulates from the 30s, but clinical dementia typically presents later. This dissociation is central to counselling families — an early biomarker or pathology finding does not mean imminent dementia.

Prevalence, incidence, and age of onset.

• Lifetime risk of dementia in Down syndrome is over 90% (some estimates 95%+).
• Mean age at prodromal (mild cognitive impairment) presentation is about 50.8 years; mean age at dementia onset is about 53.8 years (Fortea et al., Lancet 2020).
• Roughly 70% are diagnosed with dementia by around age 54; prevalence rises to 88–100% in those over 65.
• Age-specific dementia risk has been estimated at roughly 23–55% at ages 40–49 and 75–88% by ages 60–69 (Horizon 21 European consortium, Larsen et al., 2024). Reported ranges are wide because of differing diagnostic methods (some studies report clinical dementia prevalence of 5.7–55% at ages 40–49).
• Alzheimer’s disease is the leading cause of death in adults with Down syndrome older than 35, the proximate cause in about 70% of deaths.

Longitudinal Irish data (IDS-TILDA). Trinity College Dublin’s IDS-TILDA — the only study directly comparing aging in intellectual disability with the general population, following adults 40+ — found dementia prevalence among people with Down syndrome nearly doubling over a three-year period (from about 15.8% to 29.9%), a doctor’s diagnosis of dementia in 35.5% of people with Down syndrome by Wave 3, an average age of onset around 55 (with some cases in the early 40s), and — in a 20-year follow-up (McCarron et al., 2017) — 97.4% developing dementia over the period. IDS-TILDA also found nearly 80% of people with Down syndrome and dementia developed new-onset epilepsy, versus about 11% in the general population.

How dementia presents and progresses differently.

• Behavioural, personality, and executive changes come first, not memory loss. Early signs include reduced social engagement, apathy or withdrawal, decreased enthusiasm, irritability or uncooperativeness, and decline in attention and planning (the “frontal-first” pattern), reflecting frontal-lobe vulnerability. This contrasts with the memory-first presentation typical in the general population (Lautarescu, Holland & Zaman, systematic review 2017; Alzheimer’s Association).
• New-onset seizures in adulthood are a common and important feature. Up to 75% of adults with Down syndrome and dementia develop epilepsy — a far higher proportion than in sporadic (1.5–12.7%) or autosomal-dominant (2.8–41.7%) Alzheimer’s — and a first untriggered seizure after age 40–45 is highly suggestive of symptomatic Alzheimer’s disease (Fortea et al., Lancet Neurology 2021).
• Gait changes, coordination problems, sleep disturbance, and increased noisiness or excitability may appear.
• Behavioural and psychological symptoms of dementia (BPSD) can appear early and track with underlying amyloid/tau pathology.
• Progression after diagnosis tends to be more rapid than in late-onset Alzheimer’s.

Why baselining matters so much. Because adults with Down syndrome and other intellectual disabilities begin from an individual cognitive and functional baseline, decline can only be detected by comparison to that person’s own prior functioning. Down syndrome guidance (Canadian Down Syndrome Society; NDSS) recommends establishing a baseline of cognitive and functional abilities in adulthood — CDSS materials suggest around age 30, well before risk rises — and re-screening periodically, so that change can be recognized early and reversible causes ruled out.

Rule out reversible mimics first. Hypothyroidism (strongly associated with Down syndrome, and correlated with Alzheimer’s onset timing), depression, sensory loss, sleep apnea, vitamin deficiency, and medication effects can all mimic dementia and are treatable. Guidelines stress ruling these out before attributing decline to Alzheimer’s — one more reason a good working relationship with a knowledgeable doctor matters. See Navigating Healthcare for an Adult with a Developmental Disability in Ontario.

The guideline anchor. The GLOBAL Medical Care Guidelines for Adults with Down Syndrome (Tsou et al., “Medical Care of Adults With Down Syndrome: A Clinical Guideline,” JAMA, October 20, 2020; 324(15):1543–1556) issued only one strong recommendation across all topics: screening for Alzheimer-type dementia starting at age 40 (the guideline reviewed 11,295 citations and produced 14 recommendations plus 4 good-practice statements). Screening should use symptom-based evaluation and functional baselines rather than standard general-population cognitive tests. A family-friendly version was published in 2022, and a second edition is in development. The Canadian Down Syndrome Society’s “Today & Tomorrow: A Guide to Aging with Down Syndrome” (updated 2025) is the key Canadian family-facing resource.

Other health changes that arrive with age

• Vision and hearing loss are common and often under-recognized. IDS-TILDA (Wave 3) found eye-disease prevalence rising to 19.5%, with cataracts the most common (15.9%), higher and earlier in people with Down syndrome. Hearing loss (including from treatable causes like earwax impaction) compounds communication difficulty and can mimic or mask cognitive decline.
• Osteoporosis and fractures. People with intellectual disability develop osteoporotic fractures at younger ages and higher rates. In one recent study (Burke et al., 2024), osteoporosis was objectively measured at 41% with a further 33.2% osteopenic, yet fewer than 2 in 10 had a doctor’s diagnosis — a major under-diagnosis gap. Among those aged 50+, women with intellectual disability had about 2.3× and men about 3.8× the hip-fracture rate of peers without intellectual disability.
• Earlier menopause. Menopause tends to occur earlier; in an IDS-TILDA sample the mean age of menopause was about 47.6 years, and Down syndrome guidance cites an average around 42 for women with Down syndrome — with implications for bone health (earlier estrogen loss → earlier osteoporosis risk).
• Multimorbidity and chronic conditions. IDS-TILDA found multimorbidity (2+ chronic conditions) in about 72% of older adults with intellectual disability. Thyroid disease, epilepsy, and mobility decline are notably common.
• Polypharmacy. In Ontario, among older adults with developmental disabilities receiving home care, roughly 42% were taking nine or more medications overall — and nearly 59% among group-home residents — with high rates of psychotropic use (about 63% overall, 72% in group homes) (H-CARDD, 2014). Polypharmacy raises the risks of adverse drug interactions, falls, and cognitive side effects, and warrants regular medication review.

A note on the numbers: many of these prevalence figures come from Irish (IDS-TILDA), UK, or older Ontario (2009/10 data, published 2014) sources; Canadian population-level figures specific to sensory loss and osteoporosis in this population are thin.

Spotting the early signs of decline

Watch for change, not absolute scores. The core mechanic is comparing current function to the individual’s known baseline. Families and staff should watch for change in: memory and orientation, day-to-day skills (dressing, toileting, familiar routines), continence, gait and coordination, sleep, mood and social engagement, and new behaviours. Keeping a simple log of when changes appear helps distinguish stable lifelong traits from genuine new decline.

Screening tools designed for this population.

• NTG-EDSD (National Task Group Early Detection Screen for Dementia): an informant-based (caregiver-completed) screen designed specifically for adults with intellectual and developmental disabilities. It is not diagnostic; it captures early, subtle changes and pre-existing impairment to facilitate conversations with clinicians. It is free and widely used; validation work shows sections (particularly memory and language/communication) are sensitive to mild cognitive impairment in Down syndrome, but that findings need to be supplemented by fuller assessment.
• DSQIID (Dementia Screening Questionnaire for Individuals with Intellectual Disabilities): a 53-item observer-rated instrument developed by Deb et al. (2007) in the UK, with strong psychometrics (original cut-off of 20 gave sensitivity 0.92, specificity 0.97; internal consistency α=0.91). It has been translated and validated in multiple languages. Newer work (Nuebling/Wagemann et al., 2024–2026) notes limitations in specificity and in detecting early stages when relying on caregiver report alone, prompting research combining DSQIID with blood biomarkers.
• CAMDEX-DS and neuropsychological batteries (e.g., NAID) are used in specialist assessment.

The risk that real illness is missed. Diagnostic overshadowing — attributing new symptoms (pain, behaviour change, cognitive decline) to the person’s existing disability rather than investigating a new, possibly treatable illness — is a named, well-documented risk. It contributes to delayed dementia diagnosis and to missed treatable conditions. It’s covered in depth alongside co-occurring mental health under Dual Diagnosis and Diagnostic Overshadowing in Ontario: A Family Guide to Mental Health and Developmental Disability; here it’s flagged as a concept to keep in mind.

When the current arrangement no longer fits

Signs the setup needs to change. As stamina drops and health needs rise, a full-day, high-activity day program may become too demanding; living arrangements may no longer match support needs; and pace, transport, and scheduling may need adjustment. Signs include increased fatigue, new falls, withdrawal from previously enjoyed activities, and difficulty with transitions.

The poor fit of mainstream seniors’ services. Long-term care homes and generic seniors’ day programs are frequently ill-suited: staff are rarely trained in intellectual and developmental disability, communication supports are lacking, peer groups differ by decades of life experience, and admission and eligibility processes are built for the “average” senior. In Ontario, adults with developmental disabilities are markedly over-represented in long-term care at younger ages, and are over-represented among long-stay hospital and psychiatric admissions (H-CARDD/ICES) — often because appropriate community options are unavailable.

Aging in place vs. moving. Emerging best practice, supported by the NTG and by longitudinal service-provider research (e.g., the 14-year “Wichita Project” tracking 34 adults with intellectual disability and dementia across three purpose-built, five-bed dementia-capable group homes), favours “aging in place” — keeping the person in a familiar environment and bringing adapted support to them — over default admission to institutional settings. Adaptation looks like: modifying the physical environment for safety and orientation, simplifying and slowing routines, reducing group sizes, adding health monitoring, and training staff in both dementia care and intellectual-disability care. For a fuller look at residential and home models, see Housing and Residential Options for Adults with Developmental Disabilities in Ontario.

Planning for the end of life

This is hard to think about, but planning early is one of the kindest things a family can do.

End-of-life care is under-accessed. People with intellectual and developmental disabilities consistently receive worse access to palliative and hospice care:

• A large English primary-care cohort study (Tyrer, Tuffrey-Wijne et al., Family Practice 2026; 1.1 million decedents, 9,858 with intellectual disabilities) found people with intellectual disabilities were less likely to have an end-of-life care record before death (21.8% vs 28.4%), had about half the end-of-life hospitalization rate (incidence rate ratio 0.42), and were identified closer to death — 26% died within 7 days of their first end-of-life care record versus 16% of those without intellectual disabilities. Specialist palliative-care referral rates were low in both groups (~16% vs ~15%), signalling that end-of-life needs are recognized too late.
• The UK Confidential Inquiry (CIPOLD; Heslop et al., Lancet 2014), reviewing 247 deaths of people with learning disabilities across five South West England Primary Care Trusts, found that of the 238 deaths for which the Overview Panel reached agreement, 42% were assessed as premature (average age at death 65 for men / 63 for women, ~16 years younger than the general population); people with learning disabilities were less likely to access specialist palliative care and received less opioid analgesia in their final illness.
• A systematic review (Adam, Tuffrey-Wijne et al., Palliative Medicine 2020) concluded that adults with intellectual disabilities face multiple barriers and are less likely to access palliative care, and called addressing this an urgent international priority.
• A scoping review (Velepucha-Iniguez, Bruera et al., 2022) found under-referral, reduced access, communication barriers, and limited provider knowledge across 22 studies. A US 22-year CDC-WONDER analysis (9,432 decedents with intellectual disability, 1999–2020) found only 16.2% died in home or hospice versus 78.7% in a medical or nursing facility.

Advance care planning, adapted. Advance care planning for this population must be adapted to communication and cognitive needs: visual and creative tools (e.g., Talking Mats, picture- and card-based conversation resources such as “When I’m ill” and “My funeral” cards, “Books Beyond Words”) work better than standard easy-read forms, which co-design research found overwhelming (Bruun et al., JARID 2025). Planning should begin early — ideally before dementia is advanced, while the person can still participate. NTG and international-summit consensus recommends integrating disability and palliative-care providers, training carers in end-of-life support, and involving the person early in their own advance care planning. This overlaps closely with succession planning for when a caregiver is no longer there; see Future & Succession Planning in Ontario: A Guide for Aging Parents of an Adult with a Developmental Disability.

Place of death and system dependence. Place-of-death patterns vary by country and care system: English mortality reviews found people with intellectual disabilities more likely to die in hospital (59% vs 45%), whereas Irish (McCarron et al., 2017) and Swedish (Segerlantz et al., 2020) data found many people with intellectual disability dying in their group or residential home. The direction of “home death” should not be read uncritically as good access — it may instead reflect that people die where they live without hospital or hospice services. Canadian and Ontario-specific palliative-access data for this population is a genuine literature gap; the closest anchor is the H-CARDD/ICES finding that adults with developmental disabilities die prematurely at a much higher rate (6.1% vs 1.6% over 2010–2016).

What good day-program and community support looks like

Good later-life support in a day-program or community setting includes:

• Baselining and monitoring: record each person’s cognitive and functional baseline; use NTG-EDSD/DSQIID-style screening to detect change; track health, mood, sleep, gait, and continence over time.
• Adapting activities and pace: shorten days, build in rest, reduce group size and stimulation, keep routines predictable and familiar, and shift from skill-acquisition goals to comfort, engagement, and preserved abilities.
• Dementia-capable environments and programming: apply dementia-design principles (clear wayfinding, reduced clutter and noise, good lighting, safe walking paths) and person-centred approaches (e.g., Montessori-for-aging methods) adapted for intellectual disability.
• Health promotion within capacity: maintain mobility, hearing and vision aids, nutrition and hydration, and medication review.
• Staff training that bridges both fields: direct-support professionals need competency in both dementia care and intellectual-disability care. NTG offers structured “Dementia Capable Care” training, and in Ontario, Reena and the Alzheimer Society of York Region have run cross-sector one-day “Aging with a Developmental Disability” workshops for both developmental-services and health/seniors/long-term-care staff.
• Grief and continuity: support peers and staff through illness and loss; maintain relationships and familiar faces as the person declines.

Where families get stuck: the jurisdictional gap

In Ontario, two systems serve aging adults with developmental disabilities, and neither clearly “owns” them:

• Developmental services are funded by the Ministry of Children, Community and Social Services (MCCSS), delivered by community agencies, and accessed through Developmental Services Ontario (DSO) under the Services and Supports to Promote the Social Inclusion of Persons with Developmental Disabilities Act, 2008 (SIPDDA).
• Health, seniors’, home, and long-term care are funded by the Ministry of Health / Ministry of Long-Term Care and Ontario Health (home care and long-term-care placement).

The seam between them is where responsibility falls through. The H-CARDD aging report explicitly flagged that group-home residents (an MCCSS-funded setting) were relying on Ministry-of-Health-funded home care for services such as homemaking — a role “largely expected to be filled by service providers in the developmental services sector” — revealing unclear boundaries about who pays for and provides care as people age. Mainstream seniors’ programs, long-term care homes, and geriatric services are governed by health legislation and were not designed for this population, while developmental-services agencies are often not funded or equipped for dementia-level and end-of-life care. Ontario’s own guidance on supporting adults with a developmental disability in long-term care attempts to coordinate MCCSS, MLTC, Ontario Health, HCCSS, DSO, the Office of the Public Guardian and Trustee, municipal service managers, and LTC homes — the sheer number of parties illustrating the fragmentation. (As of March 31, 2022, 8,026 people receiving MCCSS-funded supportive living services were 50 or older.)

Where responsibility actually lives. Legally, developmental-services eligibility and funding sit with MCCSS/DSO; health care, home care, and long-term care sit with Health / Ontario Health / MLTC. In practice, aging adults with developmental disabilities need both simultaneously, and no single body is accountable for integrating them. Bridging efforts exist — the Ontario Partnership on Aging and Developmental Disabilities (OPADD, led through Reena), Developmental Disabilities Primary Care guidelines and the OHIP-billable annual health check for adults with developmental disabilities, Project ECHO Ontario AIDD, and the NTG Canadian Consortium/Reena work under Canada’s National Dementia Strategy — but these are largely voluntary partnerships rather than a mandated, funded pathway.

Grey areas and points of confusion

• Whether and when to screen adults with no symptoms. The GLOBAL guideline’s strong recommendation is to begin dementia screening at 40 in Down syndrome, but there is ongoing debate about screening asymptomatic adults, the risk of false positives, and how to counsel families given the long gap between pathology and symptoms.
• Which screening instrument is best. NTG-EDSD and DSQIID are both widely used but neither is diagnostic, cut-off scores vary across populations and translations, and specificity and early-stage sensitivity are debated. There is no consensus single best tool, and serial (repeated) use over time is often recommended over single assessments.
• Biomarker research in Down syndrome. Plasma and CSF biomarkers (amyloid, tau/p-tau, neurofilament light) and PET imaging show a predictable, decades-long ordered progression similar to autosomal-dominant Alzheimer’s, and clinical trials of disease-modifying therapies (via the Alzheimer’s Clinical Trials Consortium–Down Syndrome) now specifically include people with Down syndrome. But biomarkers are not yet standard clinical practice for this population, and their role in guiding care is still being defined.
• Prevalence ranges are wide. Age-band dementia prevalence estimates vary substantially (e.g., 5.7–55% at ages 40–49 across studies) because of differing diagnostic criteria and the difficulty of assessing dementia against varied baselines.
• Place-of-death disparities differ by country, and Canadian and Ontario palliative-access data specific to this population is largely absent.
• Frailty measurement is unsettled. The H-CARDD authors themselves cautioned that the Johns Hopkins Frailty Marker may overestimate frailty in people with disabilities and that disability-specific frailty measures (e.g., the Dutch HA-ID Frailty Index, the Vienna Frailty Questionnaire) are still being developed.

How current is this, and what to double-check

• Recency: The strongest Ontario population data (H-CARDD aging profiles) reflect 2009/10 data published in 2014 — now over a decade old; projections ran to 2021. Newer Ontario-specific aging data would strengthen this picture. Down syndrome/dementia clinical figures are current (2020–2026). IDS-TILDA is ongoing (Wave 5 reported 2023).
• Geography: Much of the highest-quality longitudinal evidence is Irish (IDS-TILDA), UK, or US; Canadian and Ontario-specific figures are thinner and are flagged where used. International figures should be read as indicative, not exact, for Ontario.
• Source reliability: Clinical claims are anchored to peer-reviewed research (Lancet, Lancet Neurology, JAMA, Mayo Clinic Proceedings, Family Practice, Palliative Medicine) and specialist bodies (NTG, GLOBAL Down Syndrome Foundation, Canadian Down Syndrome Society, Alzheimer Society of Canada). Some prevalence ranges are inherently wide due to diagnostic challenges. A few figures cited from advocacy or organizational materials (e.g., CDSS guides) are included as family-facing anchors and noted as such.
• Scope: This guide covers the later-life health trajectory and aging support. General (non-age-specific) health disparities, the diagnostic-overshadowing deep-dive, residential and housing models, and aging-caregiver succession planning are covered in companion guides and are only touched here where they intersect aging and care transitions. This is general information, not medical advice — decisions about screening, diagnosis, and treatment belong with the person’s own clinicians.

Related: Navigating Healthcare for an Adult with a Developmental Disability in Ontario · Future & Succession Planning in Ontario: A Guide for Aging Parents of an Adult with a Developmental Disability · Dual Diagnosis and Diagnostic Overshadowing in Ontario: A Family Guide to Mental Health and Developmental Disability · Housing and Residential Options for Adults with Developmental Disabilities in Ontario