The relationship between perceived functional difficulties and the ability to live well with mild‐to‐moderate dementia: Findings from the IDEAL programme

Objectives The objectives of the study are to investigate how different levels of functional ability relate to quality of life, well‐being, and satisfaction with life, conceptualised as reflecting capability to “live well” in people with dementia. Methods/design Participants were 1496 people with mild‐to‐moderate dementia and 1188 informants who completed baseline assessments in the Improving the experience of Dementia and Enhancing Active Life (IDEAL) cohort study. Total self‐rated and informant‐rated scores on the Functional Activities Questionnaire were split into six ability levels to monitor how poorer functioning impacts the ability to live well. We also investigated the potential influence of sociodemographic and diagnostic variables, depression, cognition, and carer stress. Results Multivariate multiple regression models found that people with dementia who had the greatest functional impairment according to self‐ratings and informant ratings had poorer living well scores than those with the least functional impairment. Sociodemographic and diagnostic factors and cognition had little impact on effect sizes. For self‐ratings, depression attenuated the relationship between functional ability and living well, whereas carer stress attenuated informant ratings. Conclusions People with dementia with the least functional impairments had greater capability to live well than those with the most functional impairment. Even subtle perceived difficulties in functional ability had a detrimental effect on the ability of people with dementia to live well. Depression in people with dementia and carer stress in informants influenced these associations, and therefore, these factors should be routinely included in future research studies and clinical assessments.


| INTRODUCTION
Dementia refers to a group of progressive brain disorders associated with largely generalised mental functioning difficulties, including memory and other aspects of cognition, behavioural disturbances, and reduced activities of daily living (ADL). 1,2 Impairment in ADL is diagnostically central to dementia. 3,4 There is a hierarchical sequence of decline in ADL that distinguishes between basic ADL and instrumental ADL. 5 In early-stage dementia, basic ADL, such as bathing, eating, and dressing, show little decline, 6 whereas instrumental ADL, such as using a telephone, managing finances, and managing medication, show noticeable decline, 7,8 and evidence suggests linkage between declining instrumental ADL and cognitive abilities. 9,10 This evidence led to the dependence framework, conceptualised as the measurable impact that concomitant cognitive and functional difficulties and increased neuropsychiatric symptoms exert as dementia severity increases. 11 The dependence framework and the "disablement process" theory propose that increased dependence negatively affects quality of life (QoL). 11,12 People with dementia identify functional independence as an important factor in enhancing their QoL. [13][14][15] In the United Kingdom, the Alzheimer's Society identifies improving the QoL of people with dementia by promoting functional ability and independence as one of its five priority goals for dementia care research. 16 Recent dementia policy has prioritised enabling people to "live well" with dementia by improving health care and the quality of support offered to people with dementia. 17,18 A primary goal for dementia care is to maximise the ability to live well with the condition. 19 Living well in people living with chronic illness and disability is defined as the best achievable health state that encompasses all dimensions of physical, mental, and social well-being. [20][21][22] While the concept of QoL concerns integration of interpersonal and health factors, as indicated above, the well-being concept can be considered as a state of equilibrium or balance, which is affected by life events or challenges, 23 while satisfaction with life entails a global evaluation of one's current life. 24 Integration of these three concepts captures a more complete understanding of what it is to live well with a particular condition. 22,25,26 Understanding the relationship between functional ability and subjective perceptions of living well is important, particularly as no preventive or curative treatment for dementia is currently available.
In people with dementia, reduced functional ability is consistently associated with higher depression, increased age, lower education, and poorer cognitive status. 2,11,[27][28][29][30][31][32] Functional ability has also been investigated concerning self-rated and informant-rated QoL in dementia, with functional difficulties leading to poorer QoL outcomes. [33][34][35][36][37][38][39] Investigating QoL in people with mild-to-moderate dementia typically involves use of either self-ratings or informant ratings, 40 and it is generally accepted that people with mild-to-moderate dementia can provide valid self-ratings. 39 In contrast, for assessing functional ability, informant ratings are the primary method of assessment, 2,41 often assumed to be the more accurate, with cognitive decline precluding the possibility of obtaining valid selfratings. 28,[42][43][44] However, higher carer stress is consistently associated with lower informant-rated functional ability 45,46 whereas carer stress is typically unrelated to objectively assessed functional performance. 32,46 We recently found that, when comparing self-ratings and informant ratings of functional ability with objective performance, people with mildto-moderate dementia were able to more accurately appraise their functional ability than their informants, with the latter typically underestimating ability. 32 In view of this finding, it is important to consider how subjective perceptions of functional ability relate to both self-rated and informant-rated living well scores.
In summary, it is timely to investigate how different levels of functional ability relate to living well in people with mild-to-moderate dementia, as this could influence the type of care and support required and the timing of appropriate interventions. The present study has two aims. Firstly, since there is evidence that people with mild-tomoderate dementia can provide accurate self-ratings of functional ability, we consider how different levels of self-rated ability and informant-rated ability relate to three indicators of living well: perceptions of QoL, satisfaction with life, and well-being. Secondly, we aim to identify whether the level of functional ability across the spectrum of impairment affects subjective perceptions of living well, controlling for relevant variables including depression, cognition, and carer stress.
The Improving the experience of Dementia and Enhancing Active Life (IDEAL) programme is a 9-year longitudinal cohort study investigating influences on living well with dementia. 25 • Even subtle difficulties in activities of daily living have a detrimental effect on the ability of people with dementia to live well.
• Depression in people with dementia and carer stress in informants need to be routinely considered in future research studies and clinical assessments. on the Mini-Mental State Examination, 48 indicating mild-to-moderate dementia, and the ability to communicate verbally in English. Exclusion criteria were comorbid terminal illness, inability to provide informed consent, and any known potential for home visits to pose a significant risk to researchers. Informants were recruited into the study if they were willing to take part and were proving regular care to the person with dementia. 49 Full criteria for exclusion and consent are provided in the protocol. 25  To measure instrumental ADL, we employed an 11-item FAQ, modified from the original 10 items to include a question concerning telephone use. 30 Each item was rated on a 0 to 3 scale leading to a score range of 0 to 33; a higher score indicated greater perceived difficulty with functional ability. Both self-rated (FAQ-S) and informant-rated (FAQ-I) versions were used in the study. FAQ scores were split into six levels of impairment. Level 1 comprised those with no reported functional impairment (FAQ 0). To indicate impairment, a cut-off score of 5 has been proposed. 47 We have previously found that this cut-off is commensurate with the amended FAQ scoring, and in our previous study, no one was reclassified as impaired using the self-rated or informant-rated amended FAQ. 30 Therefore, level 2 included those who scored 1 to 5. An alternative FAQ cut-off score of 9 has been recommended as indicative of impairment 44 and is used primarily in North America; 50 thus, level 3 included those who scored 6 to 9. The remaining three groups reflect equal score ranges comprising 8 points each: level 4 (10-17), level 5 (18)(19)(20)(21)(22)(23)(24)(25), and level 6 (26)(27)(28)(29)(30)(31)(32)(33). Participants with dementia who had no informant participating in the study were included in the analyses using FAQ-S ratings but not in the analyses using FAQ-I ratings.

| Living well
We used three measures to assess living well with dementia. These were the QoL in Alzheimer's Disease scale score (QoL-AD), 51 Satisfaction with Life Scale score (SwLS), 52

and the World Health
Organization-Five Well-being Index (WHO-5) 53,54 percentage score.
For each measure, a higher score indicates greater capability to live well: QoL-AD range 13 to 52, SwLS range 5 to 35, and WHO-5 range 0 to 100. Both self-rated and informant-rated versions of each measure were used. For convenience, the three measures together will be referred to as "living well measures."

| Cognition, mood, and carer stress
The following additional measures from the IDEAL dataset were included in this analysis. The Addenbrooke's Cognitive Examination-III (ACE-III) 55 was used to measure cognition in participants with dementia. The ACE-III is scored out of 100 with higher scores indicating better cognitive functioning. The Geriatric Depression Scale-10 (GDS-10) 56 was used to measure depression in participants with dementia, with higher scores indicating more self-rated depressive symptoms. For the purposes of the analysis, the sample was split into two groups: not depressed (GDS-10 = 0-3) and depressed (GDS-10 = 4-10). The Relatives' Stress Scale (RSS) 57 measured the level of self-reported carer stress; possible scores range from 0 to 60 with higher scores indicating greater carer stress.

| Sociodemographic and diagnostic variables
For the participants with dementia, we obtained information about age, gender, education, diagnosis, and relationship to the informant.
Participants were classified into five groups based on age (younger than 65, 65-69, 70-74, 75-79, and 80 years and older) and education (no qualifications, school leaving certificate at age 16, school leaving certificate at age 18, and university). Relationship to the informant was classified into three groups (spouse/partner, other, and no informant participating).

| Procedure
Information was collected from people with dementia and informants who were visited at home by a researcher on three occasions spread over a few weeks. Informed consent was obtained from both the person with dementia and the informant (where available). For the second research aim, as the three living well measures employed different scoring systems, scores were standardised. Multivariate multiple regression models for each rating type were repeated using the standardised scores so that the living well measures could be directly compared.

| Planned analyses
Multiple imputation was conducted to account for missing data.
Ordinal variables were imputed using ordinal regression, and categorical variables were imputed using multinomial regression. The imputed model included all variables in the analysis. Estimates from 10 imputed datasets were combined using Rubin's rules. 58

| RESULTS
The 1493 participants with dementia were in the mild-to-moderate stages. There were more men than women with dementia, and Alzheimer's disease was the most frequent diagnosis ( Table 1). The  Table S1 for mean and percentage data. The inclusion of the additional telephone use item in the amended version of the FAQ had little effect on the number of people classified as impaired; for self-rated and informant-rated FAQ, there were, respectively, five (0.3%) and six (0.5%) additional participants classified as impaired following inclusion of the additional item. There were slightly more classified as impaired with the amended FAQ using the cut-off score of 9 with 22 (1.5%) and 17 (1.4%) for self-rated and informant-rated FAQ, respectively.
3.1 | Self-rated functional ability and living well measures Table 2 reports unadjusted and adjusted coefficients between the six FAQ-S levels and the self-rated living well measures. Those whose self-ratings placed them in the most functionally impaired group had lower QoL-AD, SwLS, and WHO-5 scores compared with those in the least functionally impaired group. Coefficients reduced after adjusting for sociodemographic and diagnostic factors and slightly increased after further adjustment for ACE-III score. The largest reduction in coefficients was after adjusting for GDS-10 score.  Table S2. Table 3 reports the unadjusted and adjusted coefficients between the six FAQ-I levels and the informant-rated living well measures.

| Informant-rated functional ability and living well measures
Compared with those with the least informant-rated functional impairment, those in the most functionally impaired group had lower QoL-AD, SwLS, and WHO-5 scores. After adjusting for sociodemographic and diagnostic factors, the differences were largely unchanged. Coefficients increased slightly after further adjustment for ACE-III score,  while adjusting for GDS-10 score produced a slight reduction.
Adjusting for RSS score produced the largest reduction in coefficients.  Table S3.

| Impact of missing data on the results
The percentage of missing data was between 1.3% and 10.5% across all domains for people with dementia and between 0.2% and 6.8% for informants (see Table S1). Coefficients were generally similar to the complete case analysis, but standard errors reduced after multiple imputations. Imputation did not alter the relationships but improved the precision of estimates. well. The finding corroborates earlier studies where depression was found to separately influence functional ability and self-rated indicators of living well. 31,33,35,36,39,40,45,59 The majority of previous studies, however, have employed diagnostic classifications or informant ratings of depression. For example, a recent study found that people with dementia who had a formal diagnosis of depression rated themselves as less impaired in functional ability than people with dementia who did not have a diagnosis of depression. 28 However, they did not report current levels of depression, so it is possible that ameliorative treatment may have influenced the results. There has been relatively little research investigating the relationship between self-rated depression and functional ability in people with dementia, primarily because of a scarcity of studies employing self-rated measures of functional ability. 2 Previously, and consistent with the current findings, we found a significant association between self-rated depression and self-rated functional ability, 60 where those who were more depressed rated their functional ability as more impaired. It may be that people who are depressed are likely to overestimate functional impairments because of negative thought processes leading to an overall negative view of self, though in contrast "depressive realism" may lead to a more across the functional ability levels, which fits with the suggestion that satisfaction with life may be relatively stable; for example, there is little quantitative difference between the scores of university students and healthy older people. 68 The decreasing pattern in living well scores from the least to most functionally impaired participants supports disablement process theory where increasing disability leads to  reduced QoL 12 and is also consistent with the emphasis on depression and functional ability in Lawton's dementia-specific model of QoL. 69 The current study extends this to well-being, although after controlling for depression, self-rated satisfaction with life was not affected by changes in functional ability.

| CONCLUSION
We found evidence that people with dementia who have the least perceived functional impairments report better QoL, satisfaction with life, and well-being than those with the greatest perceived functional impairment. Perceived difficulties in instrumental ADL had a detrimental effect on the ability of people with dementia to live well even at low levels of functional impairment. The relationship between functional ability and living well was generally linear, indicating that as difficulties with everyday activities increase, the ability to live well decreases. Importantly, the study found that standardising QoL, satisfaction with life, and well-being scores resulted in effect sizes for each that were equivalent between the three measures. Therefore, functional ability contributes to the ability of people with dementia to live well. Depression in people with dementia and carer stress in informants were confirmed as confounding factors that negatively influenced ratings of functional ability and measures of living well.
Depression in people with dementia and carer stress in informants need to be routinely considered in future research studies and clinical assessments to help facilitate accurate judgements of functional ability and living well. Longitudinal studies are needed to elucidate whether the association between functional ability and living well remains as dementia severity increases further.

ETHICS STATEMENT
The authors assert that all procedures contributing to this work com-