Intellectual disability

Abstract

Purpose of review: Successful ageing has not yet been defined in people with an intellectual disability. The purpose of this review is to discuss and define successful ageing in the context of intellectual disability and to propose strategies to improve health and wellbeing for this population.

Recent findings: People with an intellectual disability experience higher rates of diabetes, hypertension, obesity and cardiovascular disease, and higher rates of mental disorders than people without an intellectual disability. People with an intellectual disability engage in more passive leisure activities because many active leisure activities require the participation of or assistance by others. Health promotion programmes tailored to people with an intellectual disability consisting of exercise and health education can result in more positive attitudes toward exercise and improvements in psychosocial outcomes.

Summary: With modifications for people with an intellectual disability, the concept of successful ageing can be used as a template for development of strategies to improve health and wellbeing for people with an intellectual disability as they age. Targeted programmes focused on health promotion and prevention of age-related morbidities is required. There is a need for policies addressing positive ageing, including social participation and maximizing community participation. Appropriate and ongoing education for people with an intellectual disability and their carers on healthy living in areas of physical, social, and cognitive activity, nutrition and avoidance of risk factors is essential.

INTRODUCTION

The world population faces a demographic challenge with doubling of the lifespan in the past century and a steadily increasing ageing population. Demographic change is also a major issue for the intellectually disabled population for whom life expectancy has also increased  [1] . This positive trend reflects improved social care and tailored healthcare, which has sought to address the health needs associated with specific disorders and severe and complex disabilities. However, as with the general population, additional years of life are not necessarily associated with absence of disease or preserved quality of life. Substantial public health initiatives have been launched to improve the health and wellbeing of older people  [2] . However, special populations for whom ageing has specific relevance, such as those with an intellectual disability, have received little attention. This is a notable deficiency, as the population with an intellectual disability has witnessed a dramatic increase in life expectancy, faster than that for the general population  [3] , and this is set to continue in the near future  [4] . In their Ageing and Intellectual Disabilities - Improving Longevity and Promoting Healthy Ageing: Summative Report, the WHO  [5]  emphasized that national health and social policies including people with an intellectual disability that provide for special supports and assistance into old age are much needed.

Longevity in people with an intellectual disability carries a substantial burden of age-related disorders, like dementia, mental ill health, cataracts, hearing disorders, diabetes, hypertension, and osteoarthritis  [6] . For example, the relative risk of dementia has been estimated to be four to five times higher for people with an intellectual disability compared with the general population  [7] . There is a greater risk of mortality and dementia or cognitive decline, in particular in people with Down syndrome who often also demonstrate an earlier onset of symptoms  [8] .

A review on successful ageing in the general population  [9]  revealed younger age, not smoking, greater physical activity, better self-rated health, and not having arthritis, depression, hearing problems, disability, and diabetes as consistent indicators of successful ageing. However, 'survivors' of physical illness and disability who maintain life satisfaction, cognitive functioning and social engagement represent a larger number of older adults than 'escapers' of physical illness and disability. Many people with an intellectual disability already have chronic diseases and/or multiple disabilities at a young age including sensory impairments, epilepsy, gastrointestinal problems, infectious diseases, congenital heart disease, musculoskeletal disorders, diabetes, and poorer mental health  [10] . During ageing, functional restrictions, multimorbidity, an unhealthy lifestyle, limited detection of risk factors for cardiovascular disease, limited participation in screening programmes, and missed diagnoses because of a lack of subjective complaints are associated with poorer health  [6] . This poorer trajectory is starkly and finally represented in mortality statistics, which demonstrate higher mortality rates for people with an intellectual disability compared with the general population  [11[black small square]] . In light of such statistics, the application of conceptual frameworks such as successful ageing may assist the shaping of health policy and promotion efforts to better meet age-related needs of people with an intellectual disability.

The aim of this review is to define successful ageing in the context of intellectual disability and to discuss strategies of successful ageing to reduce age-related morbidities and improve health and wellbeing for this population.

WHAT IS SUCCESSFUL AGEING IN THE CONTEXT OF INTELLECTUAL DISABILITY?

Successful ageing can be viewed as an interdisciplinary concept that incorporates many different aspects of the heterogeneous and multicausal processes of ageing. The conceptualization of successful ageing, therefore, reflects the complex interactions of biological, social, psychological, and medical factors. For instance, genetic influences underpin biological foundations of aging, but these interact with lifestyle choices, experiences, and perceptions of an individual to determine presence or absence of components central to successful aging such as disease and disability status  [9] .

To date, the utility of the concept of successful ageing has not been explored for people with an intellectual disability. Given the premature ageing experienced by this population, it would seem appropriate to examine how this construct may inform approaches, which mitigate age-related morbidity and premature mortality in people with an intellectual disability. Although an optimal definition and measurement of successful ageing is disputed  [12[black small square],13[black small square]] , the prevailing model by Rowe and Kahn  [14,15]  utilizes an objective approach, which can be contextualized to people with an intellectual disability. According to Rowe and Kahn, successful ageing is defined as low probability of disease and disease-related disability, active engagement with life, and high physical and cognitive capacity, with all three criteria having to be met to 'qualify' for successful ageing. However, this definition presents immediate difficulties for people with an intellectual disability because the enduring nature of this disability is not readily accommodated. Further, throughout the lifespan, people with an intellectual disability have higher rates of other disabilities related to physical and mental disorders, which according to this definition precludes them from being considered to be successfully aging. Compared with the general population, fulfilment of the 'active engagement in life' criterion has more complex and extraneous determinants for people with an intellectual disability, who are heavily reliant on adequacy of disability-related supports and societal approaches to disability. Finally, the requirement for 'intact cognitive functions' in the definition is technically not met by any individual with an intellectual disability. It has been questioned how the successful ageing model by Rowe and Kahn can be applied to people with a physical disability  [16] ; however, research on what successful ageing encompasses for people with an intellectual disability is lacking. Proposed modifications which account for some of these difficulties and strategies of successful ageing with a focus of what is known in people with an intellectual disability are presented in the following.

Low probability of disease and disease-related disability in people with an intellectual disability

Key indicators for successful ageing in intellectual disability include good physical and mental health, healthy lifestyles and behaviours, social interaction and productivity, life satisfaction, and access to quality healthcare  [17] . A strategy for successful ageing in intellectual disability is to focus on modifiable or even preventable conditions that have been found to be predictors of successful ageing in healthy older adults like smoking and avoiding obesity. People with an intellectual disability experience higher rates of diabetes, hypertension, obesity and cardiovascular disease  [18,19] , and higher rates of mental disorders  [20]  than people without an intellectual disability. Healthcare providers, therefore, have to be prepared to manage a variety of primary and secondary conditions in people with an intellectual disability. Yet timely access to quality health services and supports can be difficult for this population  [17] .

Cardiovascular risk factors like hypertension or obesity in midlife can increase the likelihood of dementia later in life  [21] . Hypertension is the leading risk factor for global mortality, followed by tobacco use, high blood glucose, and obesity  [22] . People with an intellectual disability show higher rates of cardiometabolic morbidity and are more likely to lack awareness of negative health impacts of certain risk factors like obesity, and thus may be less motivated to lose weight  [23] . A recently published algorithm for supporting positive and preventive cardiometabolic health in people with an intellectual disability with detailed treatment recommendations and appropriate educational materials is a recently launched tool to assist reducing cardiometabolic morbidity in this population  [24[black small square]] .

Obesity is more common in people with an intellectual disability than in the general population and is a risk factor for chronic disorders like hypertension, diabetes, sleep disorder, heart, and respiratory diseases  [25,26] . People with an intellectual disability often have a lower income status than the general population and it has been shown that limited income is related to a lower likelihood of eating healthy food  [26] . Social stigma and resulting feelings of isolation have also been linked to excessive eating as a compensatory mechanism in people with an intellectual disability  [23] . Some cardiovascular risk factors like hypertension, diabetes, and obesity can be controlled or modified by a healthy diet. Rather than isolated supplements, a change in dietary pattern seems to be beneficial. A lower likelihood of dementia, slower cognitive decline, and reduced stroke risk are associated with adherence to the Mediterranean diet  [27] . This diet is characterized by high intake of fruits, vegetables, whole grains, nuts, legumes, and olive oil; moderate consumption of fish and seafood; low to moderate intake of cheese, yogurt, poultry, and eggs; low consumption of red meat, sweets, and saturated fats like butter; and drinking alcohol (mainly red wine) in moderation.

In addition to the recommended Mediterranean diet, an annual cardiometabolic monitoring including activity levels, diet and lifestyle, weight/waist circumference, socioeconomic resources, blood pressure, glucose regulation, fasting blood lipids, and psychotropic prescription is recommended  [24[black small square]] .

Intact physical and cognitive functions

The World Health Organization has identified physical inactivity as the fourth leading factor for global mortality  [22] . A lack of physical activity during midlife has been associated with a double increased risk of cognitive impairment in old age  [21] . In line with this, several studies have shown that physical activity is a protective factor against cognitive decline and dementia  [28-30] . A study by Australian researchers found that exercise can even improve memory function in older people  [30] . It has been shown that a 1-year aerobic exercise intervention in older adults without dementia led to a 2% increase in hippocampal volume. Consequently, the increased hippocampal volume was associated with better memory performance  [31] . The underlying mechanisms of how exercise improves cognition and reduces the risk for cognitive decline and dementia are still being investigated. One mechanism is the benefit to cardiovascular health with lowering blood pressure and obesity and increasing the blood flow and level of oxygen in the brain. Other mechanisms include neurogenesis, anti-inflammatory actions of exercise and an increase in certain neurotransmitters  [32] .

It is important that exercise is done regularly to benefit from it. At least 150 min/week of aerobic exercise, for example, brisk walking, swimming, or cycling is recommended  [22] . These recommendations can be applied to older people with an intellectual disability. However, based on specific health conditions for each individual with an intellectual disability, like cardiovascular disease or mobility restrictions, an exercise programme should be developed and monitored in consultation with healthcare providers. People with an intellectual disability have lower levels of physical fitness  [33]  and focused health intervention programmes should address this fact and raise motivation to exercise. Heller et al. [34]  showed that a health promotion programme consisting of exercise and health education can result in more positive attitudes toward exercise and improvements in psychosocial outcomes in people with Down syndrome. The authors found that access barriers, like difficulty in accessing equipment and fitness facilities and finding people to explain the exercises and to do the exercises with them, prevents participation in exercise programmes. In addition, cognitive-emotional barriers to exercise participation were reported like lack of energy, being too lazy, and the feeling that exercise was boring and too difficult. Extensive health education programmes tailored to people with an intellectual disability are needed to educate about positive effects of exercise and reinforcement of confidence in the ability to perform physical activity.

Prospective population and cohort studies suggest that cognitively stimulating activities like reading, learning new skills and languages, doing crossword puzzles, and playing games can help to delay cognitive decline  [35[black small square]] . Cognitive training interventions focusing on improvement of cognitive functions like memory, attention, and executive functions have been developed with the aim to delay, reduce, or even prevent cognitive decline. Although there is growing evidence of the benefit of cognitive training interventions, systematic and structured guidelines for the implementation of cognitive training programmes are warranted  [36] . There is a lack of studies on cognitive interventions in intellectual disability and important questions for future studies are whether cognitive interventions generalize to improvements in activities of everyday living and whether older people with an intellectual disability benefit the same way from cognitive interventions as their nondisabled peers.

Active engagement in life

Increasing age can lead to less social interactions as a result of retirement, loss of friends and family, physical decline, and increasing immobility. In addition to these unfavourable age-related changes, people with an intellectual disability have lower levels of social and civic participation, limited social networks, and restricted social roles compared with their nondisabled peers  [37[black small square],38] . Many with an intellectual disability will not marry or have children, will have limited wealth or income, and many will use support services to access leisure activities  [3] . A large study with more than 5000 nonintellectual disabled older participants without dementia showed that engaging in stimulating activities at least twice a week cut the risk of developing dementia over a 4-year period in half compared with people who were less active  [39] . These results stood independently of the education level and cognitive functioning of the sample. Notably, passive leisure activities like watching television did not reduce the risk of developing dementia. Another recent population-based study with a 20-year follow-up period showed similar results of a 45% reduced risk of dementia for those with high engagement in leisure and social activities  [40[black small square]] . Longitudinal studies investigating these findings in older people with an intellectual disability are required.

Younger people with an intellectual disability have been found to engage in more passive leisure activities and this is partly because of the fact that more active leisure activities require the participation or assistance by others  [41] . There is a need for support to empower people with an intellectual disability at all ages to engage in an active social lifestyle. There is evidence that planned movement from congregate to community settings may result in greater connectedness  [42[black small square]] . Future research should investigate barriers and enablers to participation in stimulating social activities and the impact that enhanced participation has on the ageing process/health outcomes.

CONCLUSION

Targeting lifestyle choices and healthy behaviour like avoidance of tobacco, increased physical and cognitive activity and a healthy diet may result in substantial gains in longevity, quality of life, and functional capability in people with an intellectual disability.

Often service providers and/or general practitioners are not familiar with the complex needs of ageing adults with an intellectual disability  [43[black small square]] . Communication difficulties and motor impairments are potential barriers to certain service provisions including exercise and social activity programmes. However, rather than excluding people with an intellectual disability from healthy lifestyle programmes, improved strategies and efforts to develop programmes targeted at the ageing intellectual disability population are needed. Age-supportive policies should focus on promoting healthy ageing. Appropriate and ongoing education for people with an intellectual disability and their carers on healthy living in areas of physical, social, and cognitive activity as well as in nutrition and avoidance of risk factors is essential. It should be noted that the population with an intellectual disability is highly heterogeneous with regard to their abilities and their biological, psychological, and social background, and thus a 'one-type-fits-all' approach to successful ageing is unlikely to be successful.

Despite evidence of beneficial health effects and improvement of the quality of life during ageing through physical activity and healthy diet, there has been little research on interventions to promote increased physical activity or healthy lifestyle in people with an intellectual disability. Health promotion programmes should be targeted for people with an intellectual disability to reduce barriers to healthy lifestyles.

Acknowledgements

None.