Decision-Making Capacity in Mild Cognitive Impairment

When a parent in Sydney begins forgetting bill due dates or a partner in Brisbane repeatedly misplaces car keys, the question often arises quietly: are these signs of normal ageing or something more? Mild cognitive impairment sits in that uncertain middle ground, and nowhere does the uncertainty feel more consequential than when decisions about finances, healthcare, or future living arrangements come into focus. At the heart of clinical care lies a deceptively simple question: does this person still have the capacity to decide?

For neuropsychologists, capacity is neither a single score on a test nor a yes-or-no verdict from a lawyer. It is a functional judgement that blends cognition, communication, and an individual's values, weighed against the complexity of the choice in front of them. With the number of Australians living with cognitive impairment projected to grow alongside an ageing population, clinicians across the country are sharpening their approach to this delicate work.

What Capacity Actually Means

Capacity refers to a person's ability to understand information relevant to a decision, appreciate how that decision applies to their own situation, reason through the options, and communicate a consistent choice. In Australian clinical practice, the term is preferred over older labels such as "competence," which remains a legal designation rather than a clinical one. The distinction matters because a clinician can describe cognitive strengths and limitations, but only a tribunal or court makes a binding determination of legal capacity.

MCI complicates this picture. A person with mild cognitive impairment may perform well on simple tasks like deciding what to wear in the morning, yet struggle with the layered implications of appointing an enduring power of attorney or consenting to a surgical procedure. Capacity is therefore decision-specific, time-specific, and often fluctuating, a reality that demands ongoing assessment rather than a single judgement.

How MCI Alters the Building Blocks of Choice

The cognitive architecture supporting autonomous decision-making includes memory, executive function, language, and social cognition. In MCI, episodic memory is most often affected, particularly when the underlying pathology hints at Alzheimer's disease. Patients may forget conversations with their general practitioner in Perth or misremember the side effects of a newly prescribed medication discussed the week before in Adelaide.

Executive dysfunction adds another layer. Planning a weekly budget, weighing the long-term consequences of moving into residential care, or resisting undue influence from a relative requires mental flexibility and working memory. When these processes falter, choices can drift away from a person's authentic values, even if their basic reasoning appears intact on a brief bedside test.

Tools Used by Australian Clinicians

Australian memory clinics typically rely on structured instruments to anchor their assessments. The MacArthur Competence Assessment Tool for Treatment (MacCAT-T) remains the gold standard in many tertiary centres, while the Aid to Capacity Evaluation offers a faster screen for general practice. Structured interviews help reduce cultural and linguistic bias, particularly for patients from culturally and linguistically diverse backgrounds who form a significant share of older Australians in cities such as Melbourne.

Tool	What It Assesses	Typical Setting	Approximate Duration
MacCAT-T	Understanding, appreciation, reasoning, expressing a choice about treatment	Hospital or memory clinic	15–30 minutes
Aid to Capacity Evaluation (ACE)	Screening for capacity to consent to medical treatment	General practice or bedside	5–10 minutes
Hopkins Competency Assessment Test (HCAT)	Comprehension, judgement, appreciation, choice across domains	Research or outpatient clinic	10–15 minutes
Decision-Making Capacity Assessment Tool (DCAT)	Everyday decisions, finances, living arrangements	Community or aged care	20–40 minutes

Cultural and Family Contexts

Capacity assessments rarely occur in a vacuum. In Australia, family structures vary widely, from multigenerational households in Western Sydney to older adults living independently in inner-city Brisbane apartments. Clinicians are encouraged to explore who the patient trusts, how decisions have traditionally been shared, and whether an interpreter is needed. Culturally informed assessment respects the patient's identity while still meeting the legal threshold for informed consent.

Family meetings, when conducted sensitively, can illuminate a patient's long-standing preferences and reduce the risk of undue influence. They also offer an opportunity to introduce advance care planning, which has gained traction in Australia through national frameworks and the uptake of My Health Record.

Legal Frameworks Across the States

Australia lacks a single national capacity statute, and clinicians must navigate a patchwork of state and territory laws. In New South Wales, the Guardianship Act 1987 (NSW) governs substitute decision-making, while Victoria relies on the Guardianship and Administration Act 2019. Queensland uses the Guardianship and Administration Act 2000, with the Queensland Civil and Administrative Tribunal making most capacity orders. Western Australia, South Australia, Tasmania, the Northern Territory, and the ACT each maintain their own regimes, creating real complexity for clinicians working across borders or via telehealth.

Advance care directives, recognised in every jurisdiction, allow a person to record preferences for future care while they still have capacity. When MCI is detected early, completing or reviewing an advance care directive becomes a meaningful clinical priority.

Supporting Choice Rather Than Replacing It

The contemporary shift in Australia, mirrored in the Aged Care Quality Standards, emphasises supported decision-making over substituted judgement wherever possible. Simple strategies, such as presenting information in plain English, breaking complex choices into smaller steps, offering written summaries, and allowing extra time, can preserve autonomy for people with MCI.

Clinicians are also encouraged to revisit capacity periodically, since MCI may remain stable, progress to dementia, or occasionally improve if an underlying cause such as medication side effects or depression is treated. Continuity of care, anchored in a trusted general practitioner or memory clinic, makes this ongoing monitoring realistic.

Practical Recommendations for Clinicians

• Adopt a decision-specific approach: assess capacity in relation to the actual choice at hand, not as a global label.
• Use a validated structured tool such as the MacCAT-T or ACE, supplemented by clinical interview.
• Screen for reversible contributors to cognitive change, including sleep apnoea, polypharmacy, and depression, before concluding that capacity is permanently impaired.
• Document the assessment clearly, including the information disclosed, the patient's understanding, and any supports offered.
• Encourage early advance care planning and review existing directives regularly.

Wherever neuropsychology meets daily life, the work of assessing capacity demands humility, rigour, and a steady commitment to the person behind the diagnosis. Practitioners gathering in Prague at the INS 2018 mid-year meeting will find these themes echoed throughout the scientific programme, where advances in measurement and care continue to evolve side by side.