South Korea is experiencing rapid growth in the aging population. In 2018, residents aged 65 years and older represented 14.3% of the total population, and the aging population will rise to be over 21% of the total population over the next decade [1
]. The substantial aging population creates burdens for the management of chronic diseases for both individuals and society by increasing the risks for functional impairment and disabilities [2
]. Among the chronic disease, diabetes is one of the most common in older adults, with approximately 18.8% of adults aged 65 years or older having diabetes worldwide, which is expected to double by 2045 [3
]. In Korea, the prevalence of diabetes among older adults was reported to be 28.3% in 2018, which is expected to speed up with the rapid growth of the aging population [3
Diabetes in older adults is unique and different from the presentation of diabetes in other age groups, as it is simultaneously influenced by both the degenerative aging process and abnormal glucose metabolism [5
]. Both aging and diabetes independently increase an individual’s risk of impairment in their functional abilities in daily living and psychological well-being [7
]. Having diabetes is a stressful life event that increases the burdens for older adults owing to the daily therapeutic regimen for diabetes and diminishes older adults’ functional abilities [9
]. The double burden of aging and diabetes makes older adults more vulnerable physically, psychologically, and socially, and thus, reduces their perceived health status and quality of life [8
Fatigue is a commonly experienced condition of daily life and has been defined in various ways depending on the context. It often refers to tiredness, lack of energy, or weariness [11
]. Research suggests that approximately 20% of adults experience fatigue, which generally increases with age [13
]. Furthermore, fatigue is a persistent complaint of diabetic individuals and is reported more than twice as much as in non-diabetic individuals [14
]. Considering that aging and diabetes are independent risk factors for fatigue, older adults with diabetes may be more susceptible to fatigue, compared to both younger adults with diabetes and older adults without diabetes [8
]. However, little data is available on the prevalence and severity of fatigue in older adults with diabetes.
Diabetes fatigue has vicious cyclic relationship with numerous factors, including diabetes symptoms, diabetic complications, other endocrine disorders, emotional distress, and lifestyle factors [16
] and, in turn, it negatively influences emotions, lifestyle, and blood sugar control, increasing the risks for physical and psychological diabetes complications [17
]. While diabetes fatigue has been conceptualized in several ways [16
], the existing conceptual frameworks have been limited in their ability to comprehensively encompass the multidimensional characteristics of fatigue, including those related to biological, psychological, social, and environmental contexts. The dynamic biopsychosocial (DBPS) model provides a dynamic, ecological perspective of health, which views health as being determined by the interactions between biological, psychological, and social dynamics [20
], and could be a useful conceptual framework for understanding the multidimensional properties of diabetes fatigue. Thus, the purpose of this study was to examine the multidimensional factors of fatigue for community-dwelling older adults with diabetes using the DBPS model.
The DBPS model is an expansion of the biopsychosocial model, which utilized an ecological perspective of the multidimensional health characteristics based on general systems theory [21
]. Different from the biopsychosocial model, in the DBPS model, social factors were specifically divided into interpersonal factors and macrosystem contextual factors. The model explained human health as a consequence of the reciprocal influences of biological, psychological, interpersonal, and contextual factors. Each factor represents a set of interactive forces or systems that affect health. The impact of these factors on health is viewed as being dynamic, emphasizing that their levels of influence are continually changing over time rather than being fixed. The significance of the impact of each factor varies over time, which is referred to as centrality.
Biological dynamics capture the physical elements of the body that affect health. Each functional system is a complex, interconnected set of structures and cells that play a unique but reciprocal role in maintaining health. Psychological dynamics encompass multiple interdependent psychological factors, including variables of cognition, emotions, personality, attitudes, and behaviors that affect health. Interpersonal dynamics include the effects of actual and perceived social contacts on the dyadic and group processes affecting health. Interactive interpersonal dynamics include the entities with which an individual comes into direct contact (e.g., family members, work environments, peers, and community health resources) as well as the reverberating consequences of other’s actions that indirectly affect an individual’s health (e.g., spouses’ employment status and working environment and training of health care providers). Contextual dynamics include a broad pattern of shared culture, norms, policies, and values, which shape interpersonal, psychological, and biological factors.
In this study, diabetes- and aging-related biological, psychological, interpersonal, and contextual factors were incorporated in the DBPS model to investigate the multidimensional characteristics of fatigue in older adults with diabetes (Figure 1
). The biological factors included age, gender, years with diabetes, having comorbidities, and obesity. Psychological factors included depression, sleep quality, diabetes diet-related quality of life, and perceived social support. Interpersonal factors included marital status, living arrangements, and having meal companions. Contextual factors included socioeconomic status, such as education level and household income.
shows the severity and prevalence of fatigue for the participants. The mean score of fatigue was 3.94 (SD
= 1.81, range 1–7). The prevalence of moderate and severe fatigue was 17.0% and 31.8%, respectively.
Based on the results of the univariate analysis using ANOVAs, differences in fatigue severity were found for the psychological, interpersonal, and contextual factors but not for biological factors (Appendix A
). The severity of fatigue was significantly different between some psychological measures. The fatigue score was higher in those who were more depressive (p
< 0.001), had poorer sleep quality (p
= 0.001), and had difficulty in meal planning (p
= 0.012). Among the subscales of diabetes diet-related quality of life, it was only found that the fatigue score was higher in those who were less satisfied with their diet (p
= 0.004). There was no difference in fatigue by the median value of perceived social support. Among the variables characterized as interpersonal factors, there were no significant differences in fatigue by marital status and living arrangement, whereas significant differences by eating situation were found, like exclusively eating alone (p
= 0.037) and frequency of eating out (p
= 0.028). As to the contextual factors, those whose income was less than the minimum cost of living had higher levels of fatigue (p
Results of the multiple regression demonstrated that the significant predictors of fatigue severity were depression (B
= 0.187, 95% CI (0.098, 0.276)), poor sleep quality (B
= 0.642, 95% CI (−0.029, −1.255)), difficulty with meal planning (B
= 0.233, 95% CI (0.051, 0.415)), and satisfaction with diet (B
= −0.090, 95% CI (−0.172, −0.007); adjusted R2
= 0.290, p
< 0.001; Table 2
). The prediction models of biological, interpersonal, and contextual factors were not statistically significant.
Using simultaneous multiple regression, the final model included all variables to simultaneously adjust for biological, interpersonal, and contextual factors as potential confounding factors (Table 3
). The results indicated that poor sleep quality (B
= 0.762, 95% CI (0.095, 1.428)) was the most strongly associated with fatigue, followed by comorbidity (B
= 0.752, 95% CI (0.096, 1.408)) (Table 3
). Other psychological variables, including depression (B
= 0.166, 95% CI (0.066, 0.265)), difficulty with meal planning (B
= 0.291, 95% CI (0.091, 0.490)) and satisfaction with diet (B
= −0.133, 95% CI (−0.219, −0.047)), remained significant in the model (Adjusted R2
= 0.319, p
< 0.001). The influence of diet-related variables on fatigue increased after controlling for potential confounding factors.
This study was guided by the DBPS model and examined the multidimensional factors that were related to fatigue in a sample of community-dwelling older adults with diabetes. The differences in the severity of fatigue were associated with psychological, interpersonal, and contextual factors, but not for biological factors. In the simultaneous multiple regression model, comorbidity and psychological factors, including depression, poor sleep quality, satisfaction with diet, and difficulties with meal planning, were identified as being significant predictors for fatigue severity in older adults with diabetes.
The prevalence and the severity of fatigue in this study were found to be higher than previous reports of fatigue in the general population of older adults [38
]. Although it is generally acknowledged that aging itself is a risk factor for fatigue [11
] and that older adults with diabetes are more vulnerable to fatigue compared to adults without diabetes [24
], results have been inconclusive regarding the association between fatigue and aging [14
]. Studies that have used the same instruments used in the current study showed mixed results regarding differences in the prevalence of fatigue between younger and older adults [14
]. This study also did not find the presence of a significant relationship between fatigue and age in this sample of older adults, identifying no differences between the individuals aged 65–74 years and those aged 75 years or older. One possible explanation for the mixed results for the association of fatigue and age might be variations in the prevalence of self-reported fatigue across studies depending on the variance of the measurement tools, time frame for measurement, and characteristics of the study population (e.g., clinical or subclinical conditions, physical and psychological functionality, and sociocultural background) [40
]. Another possible explanation could be that increased fatigue may be associated with a variety of age-related changes rather than being solely influenced by age itself [11
]. For example, it is well acknowledged that diabetes, especially in older adults, is related to high comorbidity burden that increases the impairment of physical and psychosocial functionalities [5
]. Thus, older adults with comorbidities are likely to be at increased risk of experiencing fatigue comorbidities [44
]. In this study, more than 65% of participants had at least two comorbid chronic diseases, such as hypertension, arthritis, and dyslipidemia, and comorbidity was found to be the strongest predictor for fatigue among the predictors included in the model.
On the other hand, prevalence findings in this study were consistent with rates identified among the healthy older adults living independently without any chronic conditions that may be related to fatigue [39
]. These similarities could be owing to having functional independence in the daily activities for living in our sample, as this study did not limit participants’ abilities to the independent daily activities for self-care and social activities. For this reason, the results suggest that functional status or performance may be more critical factors for fatigue rather than chronological age and disease itself [39
In this study, both the prevalence of depression and fatigue among participants was 49%, which was higher than reported in a sample of healthy older adults in a previous study (depression in 44% and fatigue in 35%) [46
]. In a study by Jain et al. [16
], the prevalence of depression (53%) and fatigue (68%) in individuals with diabetes were significantly higher than in individuals without diabetes (19% for depression and 17% for fatigue). It has been found that older adults with diabetes are at increased risk for the comorbid diagnoses of depression and fatigue [18
] with the risk of fatigue in older adults with depression being twice as high as those without depression [14
]. However, the risk of having comorbid depression and fatigue increased threefold in older adults with diabetes [13
]. The high comorbidity for fatigue and depression can be explained by their commonly shared risk factors [49
]. Although there were differences in the variables examined depending on the scope and the purpose of the study, numerous factors have been identified as common factors for both fatigue and depression. For example, depressive older adults with diabetes commonly experience poor sleep quality [50
], which may lead to daytime sleep or inadequate dietary intake and increase fatigue [51
]. Furthermore, they have poor appetites and undesirable dietary patterns, leading to frequent meal skipping and inadequate and/or imbalanced dietary intake (e.g., high-carbohydrates, high-fat, and high-caffeine diet), which were known to be fatigue-induced diet [52
]. In addition, economic strain or hardship, lack of social support, and social isolation are well-known risk factors for both depression and fatigue [39
We found poor sleep quality was the second strongest predictor of fatigue in this sample of older adults with diabetes. Poor sleep quality and reduced sleep duration are well-known predictors of fatigue [56
]. Deteriorated sleep quality is the most manifested aging-related characteristics, leading to negative consequences for health and quality of life [57
]. Diabetes and poor sleep quality have a reciprocal relationship, indicating that poor sleep quality adversely influences insulin sensitivity and blood glucose control, while diabetic symptoms, such as nocturia, nocturnal hypoglycemia, and restless legs syndrome, causes sleep deprivation and fragmentation [58
]. Research has reported that 40%–70% of the older population experienced sleep disorder or poor sleep quality [60
]. The prevalence of sleep disorder was 1.4 times higher in diabetes patients, compared to those without diabetes [61
]. In this study, 71.3% of the participants reported poor sleep quality with extended sleep latency and sleep fragmentation, which was higher than rates reported in younger adults with diabetes [62
]. This finding indicates that older adults with diabetes are susceptible to poor sleep quality, which may have a negative association with fatigue. Given that poor sleep quality is associated with other psychological outcomes such as depression and poor quality of life as well as low adherence to diabetes self-management and diabetes outcomes [62
], health care providers should pay increased attention to providing appropriate interventions to improve sleep quality in older adults with diabetes.
Satisfaction with diet and difficulty with meal planning, as the diet-related psychological factors, showed strong relationships with fatigue. Dietary factors, including healthy eating, dietary patterns, and eating behaviors, have been highlighted in the diabetes literature [64
]. A recent study found that unhealthy diets led to excessive dietary energy intake, extreme dietary energy restriction, protein malnutrition, and starvation ketosis, and all of these are causes of diabetes fatigue [16
]. Zhu and colleagues [67
] reported the causal relationship of emotional eating with fatigue in adults with type 2 diabetes, but further investigation on how psychological aspects of dietary management are associated with diabetes fatigue is needed.
Satisfaction with diet is an essential component of older adults’ daily lives, especially their diet-related quality of life [68
]. Satisfaction with one’s diet generally decreased with age [69
] since degenerative aging-related physical and psychological changes negatively impact appetite and palatability as well as the physical ability to prepare food [70
]. Previous research has shown lower satisfaction with diet in older adults with diabetes compared to younger adults aged 19–64 years using the same instrument [33
]. An unacceptable or unpalatable diet can lead to poor dietary intake, resulting in malnutrition and can ultimately have adverse health effects [8
]. Furthermore, individuals with diabetes are recommended to follow diabetes dietary guidelines that include controlled energy intake, carbohydrate counting, and a balanced diet [73
]. Such changes may lead to the restriction of food choices and recipe options, which individuals have habitually, which may affect joy and satisfaction regarding one’s diet [73
]. Dietary modifications and restrictions may be more challenging for older adults who have long-established food preferences and dietary habits, further decreasing their satisfaction with their diet [68
] and is one of the reasons for the rejection or failure to adherence to diabetes dietary guidelines among older adults [76
On the other hand, dietary management for diabetes is known to be the most problematic aspect of the disease, requiring daily engagement in dietary practice [77
]. In fact, most of the individuals with diabetes were burdened by engaging in dietary self-management compared to engaging in other types of diabetes self-management like exercise, insulin injection, self-monitoring of blood sugar, and taking oral antihypertensive agents [79
]. Thus, the burdens experienced as a result of dietary self-management on daily practice may vary but generally include challenges with dietary restriction, difficulties with meal planning, barriers to dietary practice, and failure to utilize dietary self-management [80
The difficulties with meal planning were found to be another independent predictor for fatigue in this study. Older adults have more barriers to practice daily dietary self-management. The burden of economic hardship and poor physical functioning were reported as one major factor affecting daily dietary routines [76
]. For example, older adults with diabetes usually experience a financial burden to buy high-quality foods for a balanced diet because their income is reduced after retirement [83
]. Both declines in cognitive functioning and memory, as well as disabilities or impairments in physical functioning, may limit the ability to complete daily dietary routines, like food shopping, preparation, and cooking [52
]. Furthermore, the lack of social support due to changes in family structure (e.g., loss of spouse and independence of their children), may contribute to an increased need for help and support with meal preparation in older adults [71
]. These factors may lead to poor dietary adherence, which is associated with negative emotions, such as guilt and helplessness regarding dietary management [7
]. Taken together, it is plausible that prolonged psychological burdens in relation to dissatisfaction with diet and difficulty with meal planning can influence the maladaptation of a diabetes diet regimen and exacerbate the motivation and attitude to dietary self-management as well as actual engagement in dietary self-management practices [85
]. These factors may result in chronic emotional exhaustion, a type of fatigue [86
The significance of this study can be demonstrated in terms of both its practical implications and research. First, this study highlighted the susceptibility to fatigue in older adults with diabetes, suggesting the need to provide specific care for fatigue management. Second, the DBPS model provided an integrated perspective of the psychological and social manifestations of fatigue that could not be explained by conventional biomedical perspectives. Based on an understanding of multiple dimensions of fatigue, this study suggested the need for a multidimensional approach to fatigue assessment and the development of fatigue intervention. This approach to conceptualizing fatigue could be applicable to understanding disease-related fatigue in other chronic diseases and different age groups. Third, this study was the first to describe the relationship between diet-related psychological factors and fatigue in diabetes, which has been insufficiently addressed in previous empirical research. The inclusion of psychological components in dietary intervention for improving diet-related psychological difficulties and satisfaction is needed rather than solely focusing on dietary intake and diet therapy itself.
However, the study has some limitations worth noting. Due to the limited number of participants, only the variables that were identified as being either diabetes- and aging-related factors for fatigue were included in the analysis. Furthermore, multiple studies with large samples are required to confirm our results and to identify other factors related to fatigue in this population. For example, variables, such as diet-related distress or stress, adherence to a dietary regimen, and actual dietary patterns and food consumption, are needed to comprehensively explain the mechanisms of how diet-related psychological factors affect fatigue. Another limitation regarding the study’s participants was that the sample was, in general, among healthy older adults who were actively engaged in social activities in their local health and senior centers. Further research should include older adults with different spectrums of biological, psychological, interpersonal, and contextual characteristics. Furthermore, this study only included older adults; thus, the comparison of the prevalence and the severity of fatigue across age groups was not available, and the differences in the factors by age groups could not be explored. We recommend a large-scale investigation, including different age groups, to provide a comprehensive understanding of age-specific factors of diabetes fatigue, which would contribute to the development of a tailored and effective diabetes fatigue intervention.