for by differences in five broad, cross‐cultural character traits (John & Srivastava, 1999). These so‐called Big Five personality factors are (i) Openness to Experience, (ii) Conscientiousness, (iii) Extraversion, (iv) Agreeableness, and (v) Neuroticism. In brief, Openness to Experience refers to the diversity of an individual’s mental and experiential life and is contrasted with closed‐mindedness. Conscientiousness refers to social impulse control and is typified by actions like goal‐directed behaviour and adherence to norms and rules. Extraversion refers to an energetic and engaged approach to the social world and is contrasted with introversion. Agreeableness refers to pro‐social and communally oriented behaviours and is contrasted with social antagonism. Finally, Neuroticism refers to a tendency for negative emotionality (e.g. anxiety, sadness) and is contrasted with emotional stability and even‐temperedness.
Several large‐scale cross‐sectional and longitudinal studies have investigated changes in the Big Five personality traits across the lifespan, and these studies have fairly consistently identified patterns of personality change that tend to occur in the later years of life. Specifically, people decline in their levels of Extraversion and Openness to Experience in older adulthood, while Agreeableness increases in this period of life (Donnellan & Lucas, 2008). Conscientiousness shows a curvilinear association with age, peaking in middle adulthood before declining in older age (Donnellan & Lucas, 2008). Neuroticism has shown a slight decline in later years (Donnellan & Lucas, 2008). These general trends have manifested in large samples across multiple cultures (e.g. America, Britain, Germany, Japan), albeit with more heterogeneity of change patterns observed in non‐Western cultures relative to Western cultures (Donnellan & Lucas, 2008; Chopik & Kitayama, 2018). Theoretical explanations for these patterns of change have typically emerged from the familiar dichotomy of nature versus nurture. The former contends that such changes are intrinsically programmed by our biology via countless years of evolution. The latter argues that personality change is driven by the situational demands of one’s current life stage. Through this lens, a mid‐life spike in Conscientiousness is viewed as an adaptive response to occupational pursuits in this period of life. As with most human behaviours, it seems reasonable that both intrinsic and contextual factors are at play in these changes.
Perhaps not surprisingly, several studies have linked Big Five personality factors to cognitive function and mood symptoms in older adulthood. One of the more consistent associations is that individuals with greater Openness to Experience tend to have higher overall cognitive ability and memory ability (Booth, Schinka, Brown, Mortimer, & Borenstein, 2006; Luchetti, Terracciano, Stephan, & Sutin, 2016). Openness also has been found to attenuate the effects of late‐life depression on cognitive function (Ayotte, Potter, Williams, Steffens, & Bosworth, 2009). High levels of Openness and Conscientiousness have each been associated with slower rates of cognitive decline (Curtis, Windsor, & Soubelet, 2015; Luchetti, et al., 2016). Finally, high levels of Agreeableness and Neuroticism have been negatively associated with memory and cognitive effort (Maldonato, et al., 2017). The overall effect of these personality factors on cognition is small but notable. One study found that as much as 2–7% of cognitive ability is predicted by personality factors (Booth, et al., 2006). Another study found personality factors to have a stronger correlation with cognitive performance than several medical and lifestyle factors including hypertension, diabetes, history of psychological treatment, obesity, smoking, and physical inactivity (Luchetti, et al., 2016).
Normal cognitive change with age
As discussed above, cognitive function is a major component in the psychological well‐being of older adults. Before turning our attention to abnormal cognitive ageing, we first discuss normal aspects of cognitive development in older adulthood. Ageing is associated with changes in memory and other cognitive functions throughout the lifespan. In older people, subjective cognitive complaints are common and in the lay population are typically referred to as ‘senior moments’. Specific benign cognitive changes associated with age include declines in processing speed, learning and memory, and executive functioning. Other investigators have demonstrated that declines in visual and auditory acuity contribute to cognitive change as well (Park & Schwarz, 2012). Research has demonstrated that the most pronounced function affected by ageing is processing speed, which reduces with advancing age (Salthouse, 1996; Salthouse, 2010). Importantly, normal cognitive ageing is by definition not associated with objective impairment on cognitive testing and does not result in impairment of individuals’ ability to complete daily activities.
The 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