underlying mechanisms for the cognitive changes associated with the normal ageing process have been considerably researched. Traditionally, it is thought that age‐related cognitive decline is a result of cerebral changes that include loss of volume (e.g. atrophy, particularly affecting the hippocampus and frontal lobes), degradation of myelin, loss of synapses, and cytoskeletal changes (Salthouse, 2010). Not all older adults will experience age‐related cognitive declines. Some continue to have no cognitive symptoms and remain functionally very intact well into older age (Anderton, 2002).
Abnormal cognitive ageing
While a range of cognitive changes are considered normal in the ageing population, cognitive decline beyond normal ageing is common. Approximately 14% of Americans over the age of 70 were recently estimated to have dementia, and 22% of this cohort have some form of mild cognitive impairment (MCI; (Plassman, et al., 2007; Plassman, et al., 2008). Global prevalence for dementia was estimated to be 24 million people and is expected to nearly double every 20 years, to 42 million in 2020 and 81 million in 2040 (Ferri, et al., 2005). The increased prevalence of MCI and dementia will present a significant public health challenge over the next several decades, with considerable individual, family, and societal impact, including functional deficits in daily activities, neuropsychiatric symptoms, and economic burden (Hill, et al., 2013; Wimo, Winblad, & Jonsson, 2010).
Aetiologies for mild cognitive impairment and dementia are varied. From the perspective of prognosis, these conditions generally fall into one of three categories. First, neurodegenerative dementias are characterized by progressive deterioration of cognitive and functional abilities. This category involves conditions like Alzheimer's disease, frontotemporal dementia, and Lewy body disease. A second category involves more stable or slowly progressive conditions. This includes conditions such as stroke, cerebrovascular disease, Parkinson's disease, and multiple sclerosis. Finally, a third prognostic category involves so‐called ‘reversible dementia’. Here, cognitive impairment may be remediated with the treatment of an underlying medical condition. Examples of reversible causes of cognitive impairment in older adults include normal‐pressure hydrocephalus, hypothyroidism, vitamin deficiencies, obstructive sleep apnoea, medication side effects, and mood disorders.
Mental health and cognition in the elderly and associated medical issues
The Centers for Disease Control (CDC) estimates that 20% of individuals over the age of 55 experience a mental health concern of some form, with estimates nearing 80% for those in longer‐term care settings (Conn, Herrmann, Kaye, Rewilak, & Schogt, 2007). This can manifest as anxiety, neurocognitive impairment, and/or mood disorders, including unipolar and bipolar depression. Depression is often cited as the commonest mental health disorder in the elderly, with rates generally reported at 5–10% of the population (Skoog, 2011). The large ECA community survey identified symptoms of depression in 27% of the elderly, with the highest rates found in the 10 years before retirement age (i.e. 65), a decline in prevalence in the decade after retirement age, and another increase after age 75 (Palsson & Skoog, 1997). Often depression is not recognized or is underappreciated, not only by patients but also by their treatment providers. Thus, depression may go untreated in our older patient population. This is disheartening as we know that there are effective treatments for depression, and older adults can benefit from them greatly. Symptoms of depression in older adults can include persistently sad mood, hopelessness, pessimism, reports of feelings of emptiness, and aches and pains.
The presence of depressive symptoms, even at subclinical levels (e.g. presence of symptoms that do not meet the DSM criteria for Major Depressive Disorder), have been associated with multiple adverse health outcomes, functional impairment and disability, negative rehabilitation outcomes, and increased utilization of health care services (Bieliauskas & Drag, 2013). As such, the cost of depression is high, not only in terms of quality of life but also in healthcare dollars spent. Older adults with depression incur nearly 50% higher medical costs relative to their non‐depressed peers, even when controlled for the presence of chronic medical illness (Katon, 2003). In addition, depression in older adults can be accompanied by significant cognitive impairments and may mimic dementia. Thus, depression‐associated cognitive symptoms in older adults have historically been termed pseudodementia. However, that term is problematic as depression can accompany early cognitive change, posing a diagnostic challenge.
A common reason for referral to a neuropsychologist is to assist in the differential diagnosis of dementia versus depression, where interpretation of quantitative patterns on standardized cognitive testing can assist in the diagnostic differentiation. The cognitive domains of executive functioning, memory, and attention are often impacted in late‐life depression, and the nature and course of those cognitive symptoms differ relative to dementia. Whereas cognitive symptoms in late‐life depression often have an acute onset, Alzheimer’s dementia follows a more gradual and progressive course. Mood symptoms in late‐life depression tend to be more severe relative to Alzheimer's dementia, and the prominent mood symptom is dysphoria, while apathy is more common in dementia (Bieliauskas & Drag, 2013). Potentially further complicating the clinical picture is the understanding that depression is associated with poor adherence to medications across multiple chronic disease states often encountered in the elderly population, including hypertension, coronary artery disease, and hyperlipidemia (Grenard, et al., 2011). In turn, poor medication compliance may exacerbate chronic disease states that can lead to increased risk for cognitive compromise and contribute to accelerated morbidity and mortality.
Anxiety‐related disorders are commonly encountered in older adults, with prevalence estimates ranging from 6 to 12% of the population over age 65 (Skoog, 2011) to over 20% for caregivers of people with dementia (Mahoney, Regan, Katona, & Livingston, 2005). The accurate diagnosis of anxiety in the elderly may be complicated by the overlap of symptoms with physical medical conditions (e.g. shortness of breath, palpitations, tight chest), and thus it commonly goes undiagnosed (Koychev & Ebmeier, 2016). Indeed, it is common for anxiety symptoms to emerge in conjunction with physical illness such as COPD or congestive heart failure or with medication changes, with true physical symptoms of anxiety incorrectly attributed to the physical illness or medication side effects. Unfortunately, as is commonly found in mental health research, the presence of anxiety symptoms is associated with poorer quality of life, increased disability, and elevated mortality risk by physical cause (Brenes, et al., 2005; Bourland, et al., 2000; Tully, Baker, & Knight, 2008), which are factors that may be accelerated without identification and treatment. Importantly, comorbid anxiety and depression are common in older adult clinical populations, with accurate identification of the comorbid symptoms essential as untreated anxiety may impact response to treatment of depression (Andreescu, et al., 2007). Anxiety in dementia is also common and has been found associated with increased behavioural disturbances, which may further burden caregivers (Mega, Cummings, Fiorello, & Gornbein, 1996).
Psychosis, while often encountered in elderly individuals with neurodegenerative and neurological illness (e.g. Lewy bodies dementia), is less commonly encountered in the general non‐demented older adult population. Accurate identification can be challenged by the presence of ocular and auditory pathology, medical issues, and medication effects or the effects of polypharmacy in this population. While prevalence studies of psychotic symptoms in the elderly vary considerably, the incident of first‐onset psychosis was 5.3 per 1000 person‐years for those age 70 to 90 in the non‐demented population (Ostling, Pálsson, & Skoog, 2007). The presentation of psychosis in major depression is common in the elderly, especially in inpatient settings, with 45% of those with late‐life depression identified as having delusions in one study (Meyers & Greenberg, 1986). Often, depression with psychosis in the elderly may be intractable to medication trials, and electroconvulsive therapy may be a reasonable intervention for some patients. When considering the elderly population, the manifestation of psychotic symptoms may differ in quality and intensity relative to young patients. For example, somatic and visual hallucinations are more commonly encountered in the
