Fatigue is a symptom that is commonly seen in primary care. A study of 1,648 patients over 18 years of age in eight local primary care institutions reported that 21.1% complained of persistent fatigue for six months or less, and 8.4% reported chronic fatigue for more than 6 months.¹⁾ Chronic fatigue prevention and treatment is necessary because it interferes with activities of daily living and exerts a major impact on quality of life.²⁾ However, there is no standardized questionnaire for fatigue severity since the level of perceived fatigue is different for each person, and the physical, mental, and socioeconomic causes are diverse.³⁾ For these reasons, fatigue is difficult to study.

The causes of chronic fatigue in the primary health care study in Korea 2005 were mental factors, around 46% (stress, depression, adjustment disorders, anxiety disorders, sleep disorders, hwa-byung, alcoholism, and panic disorder), organic factors, approximately 34% (uncontrolled diabetes, asthma, chronic hepatitis, tuberculosis, thyroid function abnormality, iron deficiency anemia, fatty liver disease, sleep apnea, chronic obstructive pulmonary disease, and herniated intervertebral disc), and unknown factors, about 20%.¹⁾ It has been reported that factors related to fatigue include age, gender, body mass index (BMI), lifestyle (smoking, alcohol consumption, regular exercise, and caffeine intake), psychological state (stress, depression, and anxiety), marital status, social life, occupation, sleep disorder, and autonomic nervous system.^1,4,5)

Most previous studies considered specific conditions known to be associated with fatigue, such as illnesses (cancer,⁶⁾ ischemic heart disease, ⁷⁾ systemic lupus erythematosus,⁸⁾ multiple sclerosis,⁹⁾ etc.), and sleep disorders,¹⁰⁾ anxiety, or depression.¹¹⁾ However, there are few studies of chronic fatigue without known organic cause in the primary care setting. In a study with a primary care setting, negative life events and lack of physical fitness were related with new onset fatigue.¹²⁾ In another study, chronic fatigue symptoms treated with counseling and graded exercise for one year improved, compared to a usual care control group, but the improvement was not significant.¹³⁾ There have been randomized controlled trials on the effects of aquatic exercise in women who complained of joint pain,¹⁴⁾ and the effect of walking exercise intensity on fatigue and blood lipid changes in middle-aged women, ¹⁵⁾ but these studies were limited by being conducted on a small number of specific conditions, and did not consider previous known factors that can cause fatigue.

The present study is limited to fatigue patients without an organic cause, such as malignancy, uncontrolled diabetes, asthma, chronic hepatitis, tuberculosis, ischemic heart disease, thyroid dysfunction, or iron deficiency anemia. Lifestyle and physical factors that exacerbate fatigue, such as obesity, smoking, drinking, and sleep disorders, and intermittent medication for mental factors related to fatigue, such as anxiety, depression, stress, and sleep disorders, were evaluated in this study. We assessed the effect of changes in the amount of exercise after initiating treatment interventions on changes in the severity of fatigue according to follow-up periods over time.

The BFI used in this research has clinical usefulness in a survey measuring severe fatigue, and was also found to be suitable for measurement of chronic, moderate, and severe fatigue in another study.¹⁸⁾ The FSS was used with the BFI in this study because ths FSS can be used to discriminate fatigue from mental illness when used together with anxiety and depression measurement tools.¹⁷⁾ With the BFI and the FSS, we identified the levels of overall fatigue and fatigue within one day at each visits following the initial visit, and measured the changes in each fatigue scale.

This study targeted a specific group of patients whose fatigue was not caused by an organic disease or drug. We used questionnaires to assess anxiety, depression, stress, and quality of sleep to identify mental factors related to fatigue, so the study has greater implications for effective intervention and proper treatment in many primary care outpatient clinics managing patients with fatigue.²⁾

We divided the follow-up periods into 3 categories after the first clinic visit, and subdivided the changes for each variable such as exercise amount and fatigue, and for multiple covariables by each time category. The possibility that fatigue could worsen with additional exercise in an early phase was also considered.

Fatigue is a subjective representation, and the definition is somewhat group-dependent;⁴⁾ there are differences in the measurement of fatigue depending on the aspects of interest to the subjects being assessed. The FSS questionnaire specifically addresses whether subjects feel tired after exercise and whether they experience dysfunction after working out, but we did not use that tool efficiently, because it is limited to measurement of average final scores. The BFI is helpful in understanding the relevance of fatigue in both the general population and in patients,⁴⁾ but requires further research on intervention and treatment for improvement of function in moderate or mild fatigue.¹⁸⁾

In general, regular exercise is traditionally known to reduce fatigue in studies on both men and women.⁴⁾ In this study, the subjects were a specific group of patients who visited the fatigue clinic, but had no underlying disease. Among the subjects, 60.5% were already generally physically active or worked out with specific exercises at moderate intensity at the time of the initial visit; therefore, they could have difficulty subjectively sensing the effect of exercise intervention on their level of fatigue. If the patients already performed exercise at the beginning of the study, they rarely changed the type, frequency, and intensity of exercise in the short term. We suggested that they perform their usual exercises as much as possible, so they were unlikely to perform additional prescribed exercise.

Improper or excessive exercise can worsen symptoms in chronic fatigue patients. Follow-up for graded exercise therapy (GET) for chronic fatigue syndrome^13,26) is limited to the primary setting since it requires regular exercise assessment, an exercise prescription, and payments for care. Subjects in this study tended to overwork, which primarily accounted for their chronic fatigue without an underlying organic basis; therefore, we initially recommended adequate rest instead of exercise. We added GET after fatigue improved, so it was difficult to determine whether the initial visit represented the initiation of exercise therapy. This observational study had limitations. The changes in amount of exercise were measured solely according to time, and the amount of exercise was increased very slowly to prevent fatigue exacerbation. Moreover, no constructive exercise education was provided.

The response rate for this exercise-related survey was low, and the duration and frequency of exercise were often limited, especially for time-consuming and high-cost activities such as climbing and outdoor golf. Regular exercise requires mental and physical preparation and more time and space. We documented recommendations for additional physical activity in the electronic medical records, but most of these lacked responses at the subsequent visit. Seasonal change, family events, falls, and traffic accidents were also major obstacles preventing patients from performing physical activity.

Some patients were on sedatives or antidepressants at the initial visit, and others sometimes started medication during the follow-up period for symptom relief. They tended to take medication intermittently, further limiting the validity of the results of this study.

Further high quality research is needed on the effect of changes in the amount of exercise and changes in the level of fatigue; a randomized, controlled study comparing exercise therapy with no intervention, or a prospective study emphasizing GET and follow-up of an outpatient clinic-based protocol, are needed. Detailed information about questionnaire completion should be given to patients beforehand, to obtain more accurate responses in a self-reported survey, and increased use of short-form questionnaires can increase the response rate.³⁾ The development of new tools for recording, such as smartphone applications or use of wearable devices, are also required to supplement deficiencies in survey responses.

Development of a program with a variety of exercises as interventional treatment is also important. Those working longer than 9 hours a day are known to be at higher risk of fatigue than the unemployed,²⁾ suggesting that time is needed to recover from the fatigue caused by overwork. Regular aerobic exercise is known to be effective for the quality of sleep in healthy older people with complaints of moderate sleep disorders.²⁷⁾ Targeted 10-minute exercise in pilots deprived of sleep for 40 hours temporarily reduces fatigue because of increased alertness, but the fatigue eventually recurs within one hour after exercise. ²⁸⁾ It is important to exercise regularly in sufficient quantities in a fatigue-free state in order to obtain the benefits of exercise. This means that motivation to exercise is needed for 'too busy and have no time to exercise' people, and those who are 'always tired.' Development of a simple exercise regimen that anyone can use without time and space limitations, implementation of interval training and lifestyle changes to increase activity, and raising awareness of the negative effects of fatigue to overcome them are also needed. Environmental constraints on individual physical activity can be greater than the individual's motivation to exercise, and promotion of physical activity and exercise is needed to enable social behaviors and actions that individuals can regulate.²⁹⁾ Various types of exercise programs should be developed to increase motivation and compliance with physical activity; as one example, 'Wii Fit' is known to be effective in reducing fatigue in certain illnesses.³⁰⁾

This study did not show a significant relationship between changes in fatigue and the amount of exercise according to the follow-up period after the initial visit to a clinic.