Home Nursing for Dementia and Alzheimer’s Patients: A Complete Guide
A dementia or Alzheimer’s diagnosis changes daily life gradually but relentlessly, reshaping how a person manages the ordinary tasks that once required no thought at all. For families, the natural instinct is often to keep their loved one at home, surrounded by familiar rooms, routines, and faces, for as long as it remains safe and manageable to do so. Home nursing care makes this possible by bringing trained, compassionate professional support directly into that familiar environment, easing the burden on family caregivers while helping the person with dementia maintain dignity, comfort, and the highest functional independence their condition allows.
This guide explains what home nursing for dementia actually involves, the specific skills and techniques trained caregivers bring, how care evolves across the different stages of the disease, and practical guidance for families navigating this journey, from the earliest signs of concern through to the most advanced stages of the disease.
Understanding Dementia and Alzheimer’s Disease
Dementia is not a single disease but a broad term describing a decline in cognitive function, including memory, thinking, reasoning, and the ability to perform everyday activities, severe enough to interfere with daily life. Alzheimer’s disease is the most common cause of dementia, accounting for a majority of cases, and is characterised by the progressive build-up of abnormal proteins in the brain that gradually damage and destroy nerve cells. Other significant causes of dementia include vascular dementia, resulting from reduced blood flow to the brain, often following a stroke or a series of smaller strokes, Lewy body dementia, associated with abnormal protein deposits affecting movement and cognition together, and frontotemporal dementia, which primarily affects personality, behaviour, and language before memory. While each type of dementia has its own particular pattern and progression, all share a common trajectory of gradually increasing dependence on others for daily care, which is precisely why structured, skilled support becomes increasingly essential as the condition advances. Understanding which specific type of dementia a loved one has been diagnosed with can help families anticipate the particular pattern of challenges likely to emerge, since the sequence and nature of symptoms differ somewhat between these underlying causes even though the overall trajectory toward increasing dependence remains broadly similar.
Why Home-Based Care Is Often the Preferred Choice
Research and clinical experience consistently point to the same conclusion: people with dementia generally do better, both emotionally and functionally, when they remain in a familiar environment for as long as it is safely possible. The confusion and disorientation that are hallmark symptoms of dementia are often significantly worsened by unfamiliar surroundings, a phenomenon sometimes called transfer trauma, which can occur when a person is suddenly moved to a hospital, care facility, or even a relative’s unfamiliar home. Staying in a well-known environment, surrounded by familiar furniture, photographs, and daily routines, provides a stabilising anchor that helps reduce anxiety and confusion, supporting better overall emotional wellbeing. Home-based dementia care also allows for genuinely individualised, one-on-one attention, since a home caregiver is focused entirely on a single client rather than dividing attention across many residents, as is often unavoidable in institutional settings. For many families, remaining at home also honours a loved one’s own explicitly stated wishes, since most people, when asked, express a strong preference to age and, where possible, receive care in their own home rather than in an institutional setting. This preference, well documented across numerous surveys of older adults, deserves genuine weight in family decision-making whenever it remains a safe and realistic option.
Core Services Provided Through Home Nursing for Dementia
Personal Care Assistance
As dementia progresses, everyday personal care tasks such as bathing, dressing, grooming, and toileting become increasingly difficult to manage independently. Trained home caregivers assist with these tasks in a way that preserves dignity and encourages the person to do as much for themselves as they safely can, since maintaining a sense of capability and independence, even in small ways, supports emotional wellbeing and slows the psychological impact of increasing dependence on others for such intimate, personal aspects of daily life.
Medication Management
People with dementia frequently take multiple medications, and cognitive decline itself makes it increasingly unsafe for them to manage their own medication schedule accurately. Home nurses or trained caregivers ensure medications are administered at the correct times and in the correct doses, monitor for side effects, and communicate any concerns to the treating physician, providing a critical safety net that prevents the genuinely dangerous consequences of missed doses or accidental double-dosing, a risk that grows substantially as memory impairment worsens.
Nutrition and Meal Support
Dementia can affect appetite, the ability to recognise hunger and thirst cues, and even the physical coordination needed to eat safely, sometimes leading to unintentional weight loss or, in later stages, swallowing difficulties that carry a genuine choking risk. Home caregivers plan and prepare balanced meals, offer gentle encouragement and support during mealtimes, and monitor for early signs of feeding or swallowing difficulty that may require further medical evaluation, such as referral to a speech-language pathologist experienced in swallowing assessment, since early identification of these difficulties can meaningfully reduce the risk of choking incidents and aspiration pneumonia.
Safety Supervision and Fall Prevention
Confusion, impaired judgement, and physical frailty combine to place people with dementia at significantly elevated risk of falls, wandering, and other safety incidents. Home caregivers provide attentive supervision, help identify and address environmental hazards within the home, and, particularly in moderate to advanced stages, implement specific strategies to prevent wandering, one of the most serious and anxiety-inducing safety concerns families face, often working proactively rather than simply reacting after a first incident has already occurred.
Cognitive Stimulation and Meaningful Activity
Structured, appropriately paced activities, including music, art, simple puzzles, reminiscence conversations using old photographs, and gentle physical movement, help maintain cognitive function for longer and provide genuine emotional benefit, offering a sense of purpose and engagement that significantly improves quality of life. Skilled dementia caregivers are trained to select and adapt activities to match a person’s current cognitive level, avoiding the frustration that comes from an activity pitched above their current ability while still offering meaningful engagement rather than passive, unstimulating time, since finding this precise balance often makes the difference between an activity a person genuinely enjoys and one that leaves them feeling anxious or inadequate.
Behavioural Support
Dementia frequently produces behavioural changes, including agitation, aggression, anxiety, repetitive questioning, and sundowning, a pattern of increased confusion and restlessness that tends to occur in the late afternoon and evening. Trained caregivers understand the underlying causes of these behaviours, which are almost always a form of communication reflecting an unmet need, discomfort, or overstimulation rather than intentional difficulty, and use specific, evidence-based de-escalation and redirection techniques to manage these episodes calmly and effectively, protecting both the person’s dignity and the caregiver’s own wellbeing in the process.
Coordination With the Wider Medical Team
Home nurses and caregivers often serve as the family’s eyes and ears on the ground, monitoring for changes in condition, tracking symptoms, and communicating relevant observations to the treating physician, neurologist, or geriatrician managing the person’s overall care. This ongoing, detailed observation, impossible to replicate during brief, occasional clinic visits, often proves invaluable for catching emerging health issues early and for helping the medical team fine-tune treatment over time, whether that means adjusting medication dosages or recognising a new symptom that warrants further investigation.
How Care Needs Evolve Across the Stages of Dementia
Early Stage
In the early stage, a person with dementia typically remains largely independent but may need gentle reminders, help with complex tasks such as managing finances or medications, and increasing support with driving and other activities requiring sharp judgement. Home care at this stage often focuses on companionship, light supervision, and helping establish routines and safety systems, such as medication organisers and labelled household items, that will support independence for as long as possible, and many families find this stage the ideal time to begin building a trusting relationship with a caregiver before more intensive support becomes necessary.
Middle Stage
As the disease progresses into the middle stage, memory loss becomes more pronounced, and a person typically needs more substantial help with daily activities, including bathing, dressing, and meal preparation. Behavioural symptoms, including confusion, anxiety, and sundowning, often become more prominent during this stage, and safety concerns, including wandering risk, increase meaningfully, requiring more structured supervision and specific safety measures within the home. This is often the stage at which families first begin seriously considering professional home care support, as the demands of full-time supervision start to exceed what family members alone can sustainably provide alongside their own work and family responsibilities.
Late Stage
In the late stage, a person with dementia typically requires comprehensive, hands-on assistance with essentially all activities of daily living, including eating, mobility, and toileting, and communication becomes increasingly limited, sometimes to non-verbal expression alone. Care at this stage often shifts toward comfort-focused support, meticulous attention to skin integrity and positioning to prevent pressure sores, careful management of nutrition and hydration, often including modified food textures for swallowing safety, and profound attentiveness to non-verbal cues of distress or discomfort, since verbal communication may no longer be reliably possible. Families often find this stage the most emotionally demanding, since the person’s ability to actively engage in the relationship becomes severely limited, making it especially important for caregivers to continue providing gentle, reassuring physical presence, touch, and familiar sounds such as favourite music, even when a reciprocal response is no longer possible.
Techniques Skilled Dementia Caregivers Use
Validation and Redirection Rather Than Correction
When a person with dementia expresses a belief or memory that is factually inaccurate, such as insisting on going to a job they retired from years ago, skilled caregivers avoid directly correcting or arguing, which typically causes distress and rarely succeeds in changing the person’s belief, given the nature of their cognitive impairment. Instead, they use validation, acknowledging the emotion behind the statement, and gentle redirection, guiding attention toward a different, calming activity or topic, an approach that consistently produces better outcomes for both the person’s emotional state and the caregiving relationship, and one family members can learn to apply themselves with practice.
Clear, Simple Communication
Effective communication with a person experiencing dementia involves using short, simple sentences, asking one question at a time, allowing generous time for a response, maintaining calm, warm body language and tone, and reducing background noise and distraction during conversations. These adjustments make a genuine difference in how well a person with dementia can process and respond to communication, reducing frustration for everyone involved, and are skills that family members can learn and practise alongside professional caregivers.
Consistent Routines
Predictable daily routines, with activities such as waking, meals, and bathing occurring at roughly the same time each day, provide a sense of security and reduce the confusion and anxiety that unpredictability tends to trigger in people with dementia. Skilled caregivers work to establish and maintain consistent routines, adapting only gradually and gently when change becomes necessary, since even seemingly minor disruptions can sometimes trigger disproportionate distress in a person whose cognitive flexibility has been significantly impaired.
Environmental Adaptation
Simple environmental modifications, including clear labelling of rooms and drawers, removal of trip hazards and clutter, secure locks on doors leading outside to reduce wandering risk, and good, consistent lighting to reduce shadows that can trigger confusion or fear, meaningfully improve both safety and a person’s ability to navigate their home independently for longer, often making the difference between a person retaining some independent mobility within the home and requiring constant, hands-on supervision.
Supporting Family Caregivers
Caring for a loved one with dementia is consistently ranked among the most demanding forms of caregiving, both physically and emotionally, and family caregiver burnout is a genuine, well-documented risk. Home nursing support offers essential relief, providing structured respite that allows family caregivers to rest, attend to their own health, maintain employment, and sustain the other relationships in their life, all of which are essential for their own long-term wellbeing and, in turn, their ability to continue supporting their loved one effectively. Beyond respite, experienced dementia home care providers often coach family members directly in communication techniques, behavioural management strategies, and practical caregiving skills, building the family’s own confidence and capability alongside the professional support being provided. Connecting with dementia caregiver support groups, whether in person or online, and being honest with your own doctor about the toll caregiving is taking on your own physical and mental health, are both genuinely important steps too many family caregivers delay for far too long, often out of a mistaken sense that seeking support for themselves is somehow less urgent or important than the care their loved one needs.
Choosing a Home Nursing Provider for Dementia Care
Selecting the right home care provider for a loved one with dementia deserves particular care, given the specialised skills genuine dementia care requires beyond general nursing competence. Look specifically for caregivers with documented dementia-specific training, since managing dementia’s particular behavioural and communication challenges requires distinct skills beyond standard caregiving. Ask about caregiver consistency, since people with dementia generally do better with a small, stable team of familiar faces rather than frequently rotating staff, which can itself become a source of confusion and distress. Inquire about the provider’s approach to behavioural challenges, their communication and reporting practices with family members and the medical team, and their emergency protocols. A trial period, where feasible, allows both the family and the person with dementia to assess whether a particular caregiver or agency is a genuinely good fit before committing to a longer-term arrangement, and reputable agencies will generally welcome this kind of careful, unhurried evaluation rather than pressuring families into an immediate long-term commitment.
Managing Specific Behavioural Challenges
Sundowning
Sundowning refers to a pattern of increased confusion, agitation, and restlessness that many people with dementia experience in the late afternoon and evening hours, and its exact cause remains somewhat unclear, though disrupted circadian rhythms, fatigue, and reduced light levels are thought to play a role. Strategies that often help include maintaining consistent daily routines, ensuring adequate exposure to natural light during the day, limiting caffeine and stimulating activity in the afternoon, keeping the home well-lit as evening approaches to reduce disorienting shadows, and planning calming, low-stimulation activities during this vulnerable window rather than scheduling demanding tasks or visits, since caregivers who anticipate this vulnerable window can often prevent it from escalating into a full episode of distress.
Wandering
Wandering, where a person with dementia leaves home or a safe area and becomes lost or disoriented, represents one of the most serious safety risks families face, and it is estimated that a significant proportion of people with dementia will wander at some point during their illness. Effective prevention strategies include secure door locks or alarms that alert caregivers when an exterior door is opened, identification bracelets or GPS tracking devices that can help locate a person quickly if wandering does occur, ensuring the person gets adequate physical activity and stimulation during the day to reduce restlessness, and addressing underlying triggers, such as searching for a former home or workplace, with validation and redirection rather than direct correction.
Repetitive Questioning and Behaviours
Repeatedly asking the same question or performing the same action can be exhausting for caregivers but is a genuine symptom of the person’s short-term memory impairment rather than intentional behaviour. Responding with the same patience each time, rather than expressing frustration, along with using written notes or visual cues placed in visible locations to answer common repeated questions, such as the day’s schedule, can sometimes reduce the frequency of these behaviours while also reducing caregiver strain.
Aggression and Agitation
Aggressive or agitated behaviour in dementia is almost always a response to an unmet need, discomfort, fear, or overstimulation, rather than a deliberate act, and identifying the underlying trigger, whether pain, hunger, a need to use the bathroom, or an overwhelming environment, is the most effective long-term strategy for reducing these episodes. In the moment, remaining calm, avoiding confrontation, giving the person space, and gently redirecting attention to a calming activity typically de-escalates the situation more effectively than attempting to reason or argue.
Home Safety Modifications for Dementia Care
Beyond general safety supervision, a range of specific home modifications meaningfully reduce risk for a person living with dementia. Removing or securing potentially dangerous items such as sharp kitchen tools, cleaning chemicals, and medications, installing grab bars and non-slip mats in bathrooms, securing rugs and clearing walkways to prevent trips and falls, using stove safety knobs or automatic shut-off devices to prevent kitchen accidents, and clearly labelling rooms and important items with words or pictures all contribute to a safer living environment. Password-protected or hidden controls for potentially dangerous appliances, along with monitoring systems such as door sensors and, where appropriate and used thoughtfully, video monitoring, can provide an additional layer of safety, particularly for families managing care with limited hours of direct in-person supervision.
Nutrition and Hydration Strategies
Maintaining good nutrition and hydration becomes increasingly challenging as dementia progresses, yet remains critical to overall health and comfort. Practical strategies include offering smaller, more frequent meals rather than three large ones, since this can be easier to manage for someone with a reduced appetite or shortened attention span, using simple, familiar foods that require minimal utensils or decision-making, since excessive choice can overwhelm someone with cognitive impairment, ensuring adequate fluid intake throughout the day, since thirst cues are often diminished and dehydration is a common, under-recognised problem in dementia, and, in later stages, working with a speech-language pathologist to assess swallowing safety and adjust food textures if choking risk becomes a concern. Mealtimes themselves benefit from a calm, unhurried, distraction-free environment, which supports both safety and the person’s ability to focus on eating.
Financial and Legal Planning Considerations
Dementia care decisions are rarely just medical; they frequently involve significant financial and legal planning that families are wise to address as early as possible, ideally while the person with dementia still has the capacity to participate meaningfully in these decisions. This can include establishing power of attorney for financial and healthcare decisions, documenting advance directives reflecting the person’s wishes for future medical care, reviewing and organising insurance coverage and benefits that may help offset care costs, and consulting an elder law attorney familiar with the specific legal framework in your region. Addressing these matters early, before a crisis forces rushed decisions, generally leads to outcomes that better reflect the person’s own wishes and considerably reduces stress for the family during an already difficult time.
Respite Care and Sustaining Long-Term Caregiving
Even with regular home nursing support, family caregivers benefit enormously from additional respite options that allow for longer breaks, whether for a few hours, a full day, or an extended period such as a vacation. Adult day programmes designed specifically for people with dementia offer structured social engagement and supervision during daytime hours, giving family caregivers a reliable, regular break while their loved one benefits from social interaction and activity. Short-term residential respite stays, where a person with dementia stays temporarily in a care facility, can provide family caregivers with a longer period of rest, particularly valuable during times of caregiver illness, travel, or simply the accumulated exhaustion that comes with sustained, demanding caregiving. Building a genuinely sustainable long-term care plan, one that anticipates and actively plans for respite rather than treating it as an occasional emergency measure, meaningfully reduces the risk of caregiver burnout over the often years-long course of a dementia diagnosis.
The Role of Technology in Modern Dementia Home Care
Assistive technology has become an increasingly valuable complement to hands-on home nursing care for dementia. GPS-enabled wearable devices help locate a person quickly if wandering occurs, offering families genuine peace of mind alongside the more traditional door alarms and locks. Automated medication dispensers that lock until the scheduled time and provide audible or visual reminders reduce the risk of missed or duplicated doses, particularly valuable during hours when a caregiver may not be physically present. Simple video-calling devices, designed with dementia-friendly, single-touch interfaces, help maintain connection with family members who cannot visit in person as often as they would like. Smart home sensors that detect unusual patterns, such as a stove left on or a door opened during unusual hours, can alert family members or caregivers to potential safety concerns in real time. While technology can never replace the core value of skilled, compassionate human care, thoughtfully selected tools can meaningfully extend safety and connection during the hours when direct supervision is not present.
Cultural and Individual Considerations in Dementia Care
Effective dementia care is never truly one-size-fits-all; a person’s cultural background, personal history, language, religious practices, and individual preferences all shape what genuinely comforting, meaningful care looks like for them specifically. A caregiver who understands and respects a person’s cultural food preferences, religious observances, preferred language for daily conversation, particularly important since many people with dementia lose fluency in a second language before their native tongue, and personally significant routines and rituals will generally provide more effective, comforting care than one working from a generic template. Families are encouraged to actively share this kind of personal, individualised information with home care providers, ideally documented in a simple care profile that new or covering caregivers can reference, ensuring that even unfamiliar staff can provide care that feels genuinely respectful and familiar to the person receiving it.
Transitioning to Hospice or End-of-Life Care
As dementia progresses to its most advanced stage, some families and their medical teams begin considering a transition toward hospice or palliative, comfort-focused care, which prioritises quality of life and symptom management over curative treatment. This is an emotionally significant decision, and involving the person’s medical team, ideally alongside any advance directives the person documented earlier in their illness, helps ensure the transition genuinely reflects their own previously expressed wishes wherever possible. Hospice care can often be delivered at home, alongside continued home nursing support, allowing a person to remain in familiar surroundings with focused attention on comfort, dignity, and symptom relief during this final stage, and hospice teams typically provide additional emotional and practical support to family members navigating this profoundly difficult period, both before and after their loved one’s death.
Signs a Family May Need to Increase or Reassess Care
Recognising when current care arrangements are no longer adequate is an important, ongoing part of managing dementia over its typically multi-year course. Signs that increased or reassessed care may be needed include the primary family caregiver showing signs of significant burnout, exhaustion, or declining health themselves, the person with dementia experiencing repeated safety incidents such as falls or wandering episodes despite existing precautions, noticeable unintended weight loss or signs of inadequate nutrition or hydration, worsening behavioural symptoms that current caregivers or family members struggle to manage safely, or a new medical diagnosis or hospitalisation that changes the complexity of care required. Regularly and honestly reassessing whether current care arrangements remain adequate, rather than waiting for a crisis to force the issue, generally leads to smoother transitions and better outcomes for everyone involved.
Frequently Asked Questions
At what stage of dementia should home nursing care begin?
There is no single correct point; many families begin with light support, such as companionship and help with complex tasks, during the early stage, gradually increasing the level and hours of care as needs grow. Starting earlier rather than later often allows the person with dementia to build familiarity and trust with their caregiver while they are still able to actively participate in that relationship.
Can home nursing manage all stages of dementia, including advanced disease?
Yes, home nursing can support a person through every stage of dementia, including advanced disease, provided the level and type of care is appropriately scaled, often including skilled nursing involvement for medical needs such as swallowing difficulties, skin care, and complex medication management in the later stages.
How can families tell if a caregiver is a good fit for their loved one?
Signs of a good fit include the person with dementia appearing calm and comfortable around the caregiver, the caregiver demonstrating patience and using appropriate communication techniques, and open, responsive communication between the caregiver and family. Trusting your own observations and instincts, alongside formal feedback and reporting from the care agency, is a reasonable and valuable part of this ongoing assessment.
Is home nursing for dementia more affordable than a care facility?
Costs vary considerably depending on the number of care hours needed and the specific services required, but part-time or moderate home care support is often less expensive than full-time residential facility care, at least in the earlier stages of the disease. As care needs increase toward round-the-clock support, costs can become more comparable, and families should request detailed cost comparisons specific to their situation when making this decision.
How do I talk to a loved one about needing extra help at home?
These conversations are genuinely difficult and are often best approached with empathy, patience, and a focus on maintaining the person’s independence and dignity rather than framing the change as a loss of capability. Involving the person in decisions wherever their cognitive ability allows, starting with small, low-stakes additions to their routine, and, if helpful, involving a trusted doctor to help explain the recommendation can make this transition considerably smoother for everyone involved.
Can a person with dementia refuse home care?
This is a common and genuinely challenging situation, particularly in the earlier stages when a person may still have significant decision-making capacity and limited insight into their own declining abilities. Gradual introduction of help framed as general household assistance rather than personal care, involving a trusted family member or friend in the conversation, and revisiting the topic patiently over time, rather than insisting on an immediate solution, often work better than a single direct confrontation about the need for care.
What qualifications should a dementia home caregiver have?
Look for caregivers with specific dementia care training beyond general caregiving certification, since managing dementia’s unique behavioural, communication, and safety challenges requires distinct skills. Additional qualifications such as certified nursing assistant status, first aid and CPR certification, and, for more complex medical needs, licensed nursing credentials, are also worth confirming depending on the specific level of care your loved one requires.
The Emotional Journey for Families
Beyond the practical logistics of arranging care, families navigating a loved one’s dementia journey experience a genuinely profound emotional process, often described as a form of ongoing grief, sometimes called anticipatory grief, as they watch a loved one gradually change while that person is still physically present. It is entirely normal, and not a sign of insufficient love or commitment, for family caregivers to experience a complex mix of emotions, including sadness, frustration, guilt, and occasionally relief during difficult moments, and acknowledging these feelings honestly, ideally with the support of a counsellor, support group, or trusted friend familiar with the dementia caregiving experience, supports genuine long-term emotional resilience. Many families find unexpected moments of connection and even joy throughout the caregiving journey, whether through a shared song, a familiar routine, or a brief moment of clear recognition, and holding space for both the genuine grief and these smaller, meaningful moments together tends to support a healthier long-term emotional experience than focusing exclusively on either extreme.
Building a Care Team Approach
The most sustainable, effective dementia care arrangements typically involve a coordinated team rather than a single person, whether professional or family, attempting to manage everything alone. This team might include one or more professional home caregivers providing direct daily support, family members contributing according to their own availability and strengths, the person’s primary physician and any relevant specialists such as a neurologist or geriatrician, and, where helpful, a care manager or social worker who can help coordinate the various moving pieces of care, benefits, and services a family may need to navigate. Regular communication among this team, whether through a shared logbook, a messaging group, or periodic care conferences, helps ensure everyone is working from the same understanding of the person’s current needs, recent changes, and overall care plan, reducing the risk of gaps or contradictions in care that can otherwise cause confusion and distress for the person at the centre of it all.
Conclusion
Home nursing care offers people with dementia and Alzheimer’s disease the chance to remain in the environment that best supports their emotional wellbeing and dignity, while giving families access to the skilled, specialised support this challenging condition genuinely requires. From personal care and medication management to behavioural support and meaningful cognitive engagement, trained dementia caregivers bring both technical skill and deep compassion to a role that makes an enormous difference in daily quality of life for the person receiving care and genuine relief for the family members who love them. As the disease progresses and care needs evolve, working closely with a trusted home nursing provider and the broader medical team ensures that care remains appropriately matched to each new stage, offering steady, reliable support throughout what is often one of the most challenging journeys a family will ever face together. No family should feel they must navigate this journey entirely alone, and reaching out for professional support, whether early or later in the disease course, is a sign of good, thoughtful caregiving rather than any kind of failure.
Resources for this content
- Alzheimer’s Association: Care and Support
- National Institute on Aging: Home Safety and Alzheimer’s Disease
- World Health Organization: Dementia Fact Sheet
- Alzheimer’s Society: Communicating
Disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice. Please verify this information independently and consult a qualified healthcare provider regarding the specific care needs of a person living with dementia or Alzheimer’s disease.