Abstract
Quality of life (QOL) was assessed using the EQ-5D twice in 1 year in 57 older community-dwelling people (age 79.1±5.9 years) with mild cognitive impairment in a memory clinic. Screening for sarcopenia at the initial assessment revealed 40.1% of participants (23/57) were sarcopenic. QOL declined in 33.3% of participants (19/57) after around 1 year. Multiple logistic regression analysis showed that sarcopenia was associated with a decline in QOL around 1 year after initial assessment. Sarcopenia may be a risk factor for decline in QOL in older people with mild cognitive impairment.
INTRODUCTION
As the population of Japan continues to age, the number of older people with cognitive impairment or dementia is increasing. Optimizing quality of life (QOL) is an important issue in the general older population. Moreover, cognitive decline is reported to be associated with a decline in QOL [1]. Because there are presently no curative therapeutics for cognitive impairment or dementia, maintaining QOL in the cognitively impaired population should be a priority, and factors associated with QOL in this population should be investigated.
Sarcopenia, which is characterized by a decline in muscle mass, strength, and performance, is fre-quently found in the older population and is associated with cognitive decline [2]. Sarcopenia is reported to also be associated with many unfavorable health outcomes, including falls and fractures, cardiac disease, respiratory disease, cognitive impairment, and even death, and it can negatively affect activities of daily living [3]. Some studies have suggested that sarcopenia impacts QOL in community-dwelling older people [4]. However, the association of sarcopenia with QOL in the cognitively impaired population has received little research attention.
We previously reported that sarcopenia is associated with lower QOL in a cross-sectional analysis of older people with mild cognitive decline [5]. In the present study, we investigated the association of sarcopenia with a decline in QOL over a 1-year period.
METHODS
Participants
The participants were patients attending the memory clinic of a university hospital in Japan from April in 2016 to July 2020. The last follow-up assessments were implemented in July 2021. Inclusion criteria were a Clinical Dementia Rating [6] of 0.5 (questionable) or 1 (mild dementia) and a Mini-Mental State Examination (MMSE) [7] score of 20–30. The criterion of MMSE scores > 20 was set in order to include only participants who could reliably assess their own QOL. All the participants were living in the community (not in institutions or nursing homes). Two participants (1 in sarcopenia, 1 in non-sarcopenia) lived alone. Exclusion criteria were a current serious medical or psychiatric disorder and a history of symptomatic cerebrovascular disease. The comorbidities of ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes mellitus, dementia, cancer, neurodegenerative disorders (including Parkinson’s disease) and other diseases were considered according to the Charlson Comorbidity Index [8], which represents the sum of weighted indices taking into account the number and severity of pre-existing comorbid conditions.
The study protocol was approved by the Ethics Committee of the Graduate School of Medicine, Nagoya University (2015-04356977). Written in-formed consent was obtained from all participants.
Sarcopenia assessment
Sarcopenia was diagnosed according to the criteria of the Asian Working Group for Sarcopenia (2019 consensus update) [9]. Muscle mass was measured by multifrequency bioelectrical impedance analysis (Inbody 430; Biospace, Seoul, Korea). Skeletal muscle index (SMI) was calculated by dividing muscle mass by height squared (kg/m2). The cut-off for low SMI was < 7.0 kg/m2 in men and < 5.7 kg/m2 in women. Body weight and height were measured by research nurses and used to calculate body mass index (BMI).
Handgrip strength was measured twice for each hand, and the maximum values were recorded. Gait speed was assessed in meters per second with a stopwatch as participants walked on a straight, flat path 6 m in length. Low muscle strength was defined as handgrip strength < 28 kg for men and < 18 kg for women. The criterion for low physical performance was gait speed < 1.0 m/s.
Health-related QOL
The EQ-5D is a generic and non-disease-specific instrument used to evaluate current health-related QOL [10]. The scores for the five dimensions are summed to obtain up to 3125 possible health states, from which a single index (utility) score is computed. The EQ-5D was repeated after 1 year (follow-up).
Statistical analysis
Background characteristics were compared using Student’s t-test for continuous variables or the χ2 test for categorical variables. QOL scores for the initial and follow-up assessments were compared using a paired t-test. A difference of < 0 between two QOL scores in the 1-year study period was considered to indicate a decline in QOL. In each domain of EQ-5D (mobility, self-care, usual activities, pain/discomfort, anxiety/depression) the scores were compared between baseline and follow-up by Wilcoxon signed rank test (higher numbers mean lower QOL). The likelihood of incidence of a decline in QOL was assessed using multiple logistic regression analysis.
RESULTS
A total of 149 participants completed the initial assessments of QOL and physical function, and those with sarcopenia had lower QOL (p = 0.51). Fifty-seven participants (age, 79.1±5.9 years) had follow-up assessments after about 1 year (382.7±59.1 days). There were no significant differences in background characteristics between the groups with or without follow-up assessments (Supplementary Table 1).
For the 57 participants with baseline and follow-up data, 40.1% (23/57) were sarcopenic, and the group with sarcopenia had a lower BMI and MMSE score and were older than the group (Table 1) without sarcopenia. QOL declined in 33.3% (19/57) of the participants after 1 year (Table 2). QOL was significantly lower at follow-up in participants with sarcopenia, and a paired t-test indicated a significant decline in sarcopenia. In contrast, no decline was observed in participants without sarcopenia (Table 2). No statistical differences between baseline and follow-up in each domain of EQ-5D (mobility, self-care, usual activities, pain/discomfort, anxiety/depression) in both of sarcopenic and non-sarcopenic groups (Wilcoxon signed rank test, data not shown) were observed.
Background characteristics of the participants
BMI, body mass index; SMI, skeletal mass index; MMSE, Mini-Mental State Examination; CDR, Clinical Dementia Rating; GDS, Geriatric Depression Scale; CCI, Charlson Comorbidity Index; QOL, quality of life.
QOL score in the initial and follow-up assessments according to presence of sarcopenia
Sarcopenia was found to be associated with the incidence of decline in QOL at the 1-year reassessment in multiple logistic regression analysis with adjustment for significantly different factors (age, MMSE score, BMI) between the groups with and without sarcopenia (Table 3).
Multiple logistic regression analysis of the incidence of decline in QOL.
BMI, body mass index; MMSE, Mini-Mental State Examination; GDS, Geriatric Depression Scale; QOL, quality of life.
DISCUSSION
Sarcopenia is frequently found in the older population, especially in older people with cognitive impairment. In both the present study and our previous one [5], sarcopenia was associated with a decline in QOL in older people with mildly impaired cognitive function.
Studies have suggested that non-pharmacological interventions are effective for preventing or improving sarcopenia. A combination of resistance training and protein supplementation is one effective method [11]. As such, these interventions may be useful for improving QOL or preventing its decline. Early screening of sarcopenia in people with cognitive impairment and timely intervention to prevent or improve sarcopenia is therefore warranted to maintain QOL.
Although the mechanisms underlying the association between sarcopenia and decline in QOL were not clarified in the present study, we suggest the following possibilities. Sarcopenia has been found to be associated with functional impairment and falls [12,13, 12,13], both of which can negatively impact QOL. In the present study, all of the participants were recruited from a memory clinic and were considered to be at risk of cognitive decline, and cognitive decline has been reported to be associated with a decline in QOL [1]. In addition, older people with sarcopenia are at high risk of depression [14], which can also negatively impact QOL. In this study, we adjusted for scores indicating depressive mood at the initial assessment, but subsequent incident depression in the 1-year study period was not included in the analysis. Sarcopenia is also associated with low sleep quality, which may lead to a decline in QOL [15].
Depressive mood is a risk for low QOL [16], and sarcopenia is associated with depressive mood [17]. In the current study we found that depressive mood assessed by GDS-15 was associated with decline of QOL, and the association of sarcopenia with QOL decline was independent of depressive mood.
Both of sarcopenia [18] and cognitive impairment [19] are age-dependent conditions. In the current study the association of sarcopenia with QOL decline was independent from age in the multiple logistic analysis, however, the influence of sarcopenia on QOL may be different in younger old and older old. Further studies would be warranted.
In the current study we could not find any specific domains of QOL which were affected by sarcopenia. However, it could be attributed to a lack of statistical power due to small sample size. It would be helpful to identify the domains vulnerable to sarcopenia for the development of interventions for improving QOL. Studies with more participants would be required.
The pandemic of COVID-19 in Japan started from the beginning of 2020 and in the current study 4 participants were recruited and the follow-up assessments of 11 participants were performed after the pandemic started. QOL of all these participants, who were assessed after the pandemic, did not decline (data not shown). Nonetheless, the influence of COVID-19 on QOL needs to be further explored.
This study has several limitations. First, the drop-out rate from the initial to the follow-up assessment was high (71.2%). Therefore, some bias might exist, although we did not see significant differences in the background characteristics of participants who did and did not complete the follow-up assessment. Second, the number of the participants was small, and they were recruited from a single institution. Third, the follow-up period was about 1 year, so the effects of sarcopenia on QOL over a longer time span are unclear. A multicenter study with more participants over a longer period of time is warranted.
The results of this study suggest that sarcopenia is a risk factor for a decline in QOL in community-dwelling older people with mild cognitive decline in a memory clinic.
