Study on Health/Lifestyle, Oxidative Stress, and Antioxidant Capacity Among Female Care Workers and Female General Workers

Background : Care workers have been considered to have higher work-related stress than general workers, which can have a considerable effect on their lifestyle. Hence, psychological and physiological stress levels should be examined. While several studies have investigated psychological stress among care workers, none have examined physiological stress. In addition, very few studies have been investigated the relationship between lifestyle and physiological stress. Aims : This study aimed to examine the relationship between health/lifestyle and physiological stress among female care workers and general workers and identify differences therein. Methods : Subjects included 30 workers (average age: 49.8) and 33 general workers (average age: 51.9). No significant difference in their age was noted. The “Diagnostic Inventory of Health and Life Habit” developed by Tokunaga et al. was used to examine lifestyle habits. Physiological stress was examined by measuring diacron-reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) using FRAS4 manufactured by WISMERLL Co., Ltd. during the subjects’ working hours. Results : Care workers were taller, heavier, woke up later, and slept longer than general workers. Both care workers and general workers had average health/lifestyle parameter scores that fell within the “moderate” category, with no differences between both groups. Both care workers and general workers had a poor health rating and were evaluated as “caution required,” which indicated undesirable lifestyle habits. No significant differences in d-ROMs and BAP were observed between both groups, many of whom fell under the “high oxidative stress” category for d-ROMs and “borderline” for BAP. Regarding the relationship between d-ROMs and BAP values and health/lifestyle parameters, our results found some relationship between exercise habits and d-ROMs only among care workers. Conclusion: General workers and care workers included herein had similarly poor health levels and undesirable lifestyle habits. Moreover, both groups were both had high d-ROM and normal BAP levels, with no significant differences in both indexes. Several care workers confirmed to have high d-ROMs tended to not participate in sport activities or exercise and did not to expect to benefit from them.


Introduction
Today, Japan continues to face declining birth rates and an increasing aging population, which has led to a yearly growth in the number of senior citizens needing care (2008). Moreover, in 2007, the Care Work Foundation showed that the mean turnover rate of care workers (21.6%) was higher than the overall mean turnover rate within the industry (15.4%). mental burden related to lifting assistance or bathing assistance (Kawano et al.), have been thought to promote high turnover rates among care workers.
Nakao revealed that nurses who worked like care workers suffered from similar mental and physical fatigue and that shift work considerably affected the human body and life habits. Okazaki et al. surveyed the lifestyles of nurses and care workers and clarified actual circumstances, such as weight gain, poor dietary balance, increased snacking, unsteady lifestyle, and skipping breakfast. Ono et al. reported that night shifts promoted not only irregular sleep-wake patterns but also irregular meal schedules and bowel movement timing among care workers.
The aforementioned studies suggest that irregular working hours and work overload of care workers disturb their lifestyle and promote poor physical condition owing to irregular mealtimes, lack of exercise, and sleep, weight gain by snacking, and poor nutritional balance (Okazaki et al.). Thus, care workers experience severe physical and mental stress and may have difficultly continuing labor, which subsequently leads to resignation.
A considerable number of studies on occupational stress and life-style (Ono et al., Takenaka.) have shown that stress and lifestyle are closely related. Several survey studies regarding occupational stress for reducing turnover rates among nurses and care workers (Kawano et al., Inaba., et al., Kwiatkowski., Maslach., Hayashi et al.) have also been conducted. According to the labor security hygiene findings of Japanese Ministry of Health, Labor and Welfare (2017), approximately 60% of workers experience considerable stress during work.
Stress evaluation among general workers has been widely performed through interviews, question surveys and psychiatric tests (2005, Shimomitu, Onoda et al.) However, such methods have problems with low reliability given that they are based on subjective input of the individual (Fukuda). Therefore, to objectively evaluate stress, physiological stress indexes, such as diacron-reactive oxygen metabolites (d-ROMs) (Wayner et al., Seki.) and biological antioxidant potential (BAP) (Alberti et al., Dohi et al.) in the blood, have currently been used.
Nojima et al. examined fatigue among disease-free subjects, those with chronic fatigue syndrome, those with industrial fatigue, those with high mental workload, those who survived the Great East Japan Earthquake, and other general subjects using d-ROMs and BAP. Moreover, they suggested that d-ROM accumulation is associated with various lifestyle-related diseases and promotes aging. Hence, the evaluation of d-ROMs (Wayner et al., Seki.) and BAP (Alberti et al., Dohi et al.) values can be a useful method for objectively evaluating mental and physical fatigue.
Kuragaki clarified that the d-ROMs and BAP are effective as preventive medicine of risk factors on health along with life habits and work environment and they have a possibility to contribute to people's health.
According to Komatsu et al. and Mimura et al., d-ROMs is especially influenced by diet, physical activity, and lifestyle and d-ROMs and BAP are effective tools for objectively evaluating stress among care workers.
However, studies focusing on stress among care workers based on physiological markers such as d-ROM and BAP levels are scarce. Casado et al., measured the activities of superoxide dismutase and catalase and the concentration of malondialdehyde as stress markers for care workers but did not use d-ROM or BAP levels.
Given that clarifying the relationship between work stress and lifestyle among care workers may contribute toward reducing turnover rates, the present study aimed to examine differences in health, lifestyle, and physiological stress (d-ROMs and BAP), as well as their relationship, among female care workers and general workers.

Subjects
Participants included 30 female care workers with Home Helper certification examinations over Level 2 (hereafter, care workers) and 33 female general workers (hereafter, general workers). General workers' occupations are categorized as clerical workers, medical workers, university staff, restaurant staff, and full-time homemakers. Written informed consent was obtained from all subjects after explaining in detail the purpose of this study.

Survey on Physique and Sleeping
Lifestyle items (average in a week), including awakening time, bedtime, and sleeping hours, were surveyed in addition to height and weight. Body mass index (BMI) was then calculated.

Survey on Health and Lifestyle
The National Health and Nutrition Survey (2008) developed by the Ministry of Health, Labor and Welfare has been widely used in Japan. However, its contents are limited to dietary habits, sleep conditions, favorite food, dental condition, and life and social habits. In contrast, the Diagnostic Inventory of Health and Life Habit (hereafter, DIHAL.2) (Tokunaga) developed by Tokunaga et al. (DIHAL.2) has been generally used to evaluate health and lifestyles among middle school-age to elderly individuals, as well as among various occupations, given that it can comprehensively and objectively evaluate health and lifestyle factors. The validity of the question items has also been well examined. Therefore, the current study used the DIHAL.2 to evaluate the health and lifestyle of our subjects.
The DIHAL.2 consists of 47 question items under four parameters, health status, exercise habits, dietary habits, and rest habits (hereafter health/lifestyle parameters), which are subdivided into 12 sub-factors ([1] - [12]). Subjects answered each question using a 5-point Likert-type scale (1, very low; 2, slightly low; 3, moderate; 4, slightly excellent; 5, considerably excellent). The following items outline the sub-factors and number of questions therein in parentheses.  (4) Tokunaga et al. considers the exercise, dietary, and rest parameters to represent the health/lifestyle parameters. Accordingly, a higher total score in all four parameters suggests that the subject has a healthy and desirable lifestyle. Table 1 shows the scores for all four parameters. FRAS4 is equipped with a centrifuge, a spectrometer, and a printer. After piercing a fingertip using a lancet and obtaining blood into the designated container, bleeding is stopped using a hemostatic seal. Blood cell constituents and plasma are then separated using the centrifuge, after which 10 µL of plasma is mixed into the container with a reagent exclusive for BAP or d-ROMs using a designated pipette. The container is then placed into the spectrometer for BAP or d-ROM measurement. The machine then prints out measured values of BAP and d-ROMs. d-ROMs and BAP were evaluated based on the criteria presented in Tables 2 and 3.

Statistical Analysis
Differences in the average value of each variable were determined using unpaired t-tests, while differences in the frequency of normal, borderline, and other ratings for d-ROMs and BAP test results were determined using the χ 2 test. Relationships between variables were examined using Pearson's correlation coefficient and Kendall's rank correlation coefficient. The significance level during statistical hypothesis testing was set at 5% and was controlled using the Bonferroni method.  (Table 2). Care workers and general workers had a mean BAP value of 2060.3 and 2032.6 µmol/L, respectively, with both groups falling into the "borderline" category (Table 2).

Results
No significant differences in d-ROMs and BAP were observed between care workers and general workers.  Table 5 summarizes the scores for the four health and lifestyle parameters among care workers and general workers. All four healths and lifestyle parameters among care workers and general workers fell within "moderate" and "slightly low" categories, which indicate criteria 3 and 2, respectively (see Table 1). No significant differences in all four parameters were observed between care workers and general workers.  Most of the care workers and general workers were determined to be stressed (90% vs. 73%, respectively), with only a part of them having normal d-ROMs levels. The average d-ROM value fell within the "high oxidative stress" category, with no significant difference being observed between both groups.
More than half of care workers and general workers (57% vs. 61%, respectively) had either optimum or borderline BAP values, with no significant difference being observed between both groups.  Table 7 shows the correlation coefficients and partial correlation coefficients for the relationship between d-ROMs and BAP and physical characteristics, awakening time, bedtime, and sleep duration among care workers and general workers Among care workers, d-ROMs showed significant correlation with weight and BMI.
Among general workers, however, d-ROMs was significantly correlated with weight, awakening time, and bedtime, whereas BAP was significantly correlated with height and awakening time and negatively correlated with BMI. To examine the relationship between d-ROMs and health/lifestyle parameters, we categorized the d-ROMs into three ranking parameters (normal, borderline, and others) and each health/lifestyle parameter into three ranking parameters excellent, moderate, and low that corresponded to the parameters very good/slightly good, moderate, and slightly low/very low, respectively (Table 1). Table 8 shows Kendall's rank correlation coefficients for care workers and general workers separately. Among care workers, our results showed a significant correlation only between exercise habits (Movement) and d-ROMs. No significant relationship was found between BAP and any health/lifestyle parameter among both care workers and general workers (data not shown).

Discussion
An irregular lifestyle has been known to induce not only mental but also physical stress reactions (Takenaka). Studies have shown that care workers work irregular hours (night shifts and overtime), have irregular lifestyles (meal times and bedtime), and have a wide range of work responsibilities (mobility, bathing, and toilet assistance) (Okamura et al., Ricardo et al.). Considering that care workers experience greater physical and mental burden, as well as stress, than general workers, their lifestyle habits can be easily disrupted. Nojima et al. reported that d-ROMs and BAP were associated with health conditions, lifestyle, and working conditions (Nojima.et al.).
The present study examined the differences in physical characteristics, sleeping habits, health and lifestyle, and physiological stress (d-ROMs and BAP) among female care workers and general workers based on the assumption that care workers experience greater mental and physical stress than general workers. Although no differences in age and BMI had been observed between care workers and general workers, care workers were taller and heavier than general workers (Table 4). This may be explained by the need for a large physique and decent physical fitness when caring for individuals with physical difficulties (elderly and/or disabled) who require physical assistance, such as wheelchair-mobility and toilet bathing assistance.
Given that care workers woke up later and slept longer than general workers (Table 4), the unique night and overtime work of care workers may affect their lifestyle (Ono et al.). Harano et al. reported that care workers recover from physical fatigue by taking naps during night shifts and taking adequate rest after the night shifts until the next working shift. The results of the present study showed that care workers had better physical fitness and greater sleep durations to recover from fatigue than general workers. Both care workers and general workers had average health/lifestyle parameter scores that fell within the "moderate" categories, with no difference being observed between both groups. The total heath rating for both care workers and general workers indicated  "caution required," which suggested an undesirable lifestyle, when health and lifestyle patterns were evaluated using the following four scales: (1) sufficient, (2) caution required-lifestyle, (3) caution required-health, and (4) caution required.
Tokunaga, who evaluated the average health parameter score among 182 adult men and women aged 29 or younger and 108 adult men and women older than 30, found that their scores were "somewhat excellent," which indicated a "sufficient" health rating.
The present study found that both care workers and general workers in their 50s had poor health status and lifestyles. On the other hand, a considerable amount of time had elapsed since the study by Tokunaga, and many individuals in today's society may have more stressors.
The results for general workers might have been affected by the inclusion of a significant number of personnel involved in interpersonal relationships or assistance activities (see the Methods section).
The results of the present study showed that most of care workers and general workers had been rated as stressed (90% vs. 73%, respectively), while only a small number had normal d-ROMs levels. However, no significant difference in d-ROMs levels had been observed between both groups, thus average values among care workers and general workers suggested "high oxidative stress." More than half of care workers and general workers (57% vs. 61%, respectively) had an average BAP value that fell within either optimum or borderline levels, with no significant difference between both groups. One study showed that those who live a well-regulated life usually have low d-ROMs and high BAP levels (Nagata) and tend to be evaluated as being in physiologically good condition.
Given that d-ROM levels of both care workers and general workers included herein were high, we can surmise that they had high oxidative stress and were under highly stressful conditions physiologically.
After examining 312 men and women (average age 36.7), Nojima et al. reported that d-ROMs were higher among women than men and that they increase with age. However, the same study showed that BAP exhibited no age-and sex-related differences. Komatu et al. and Trevisan et al. have shown that d-ROMs levels are easily affected by hormones and that middle-aged and older women tend to have especially high d-ROM levels due to irregular secretion of physiological hormones or menopause.
High d-ROM levels promote a loss of balance in oxidant and antioxidant reactions in the body, resulting in lifestyle-related and many other diseases (Komatu et al., Kawakami, et al.).
BAP, on the other hand, reflects the reducing ability of an organism, which prevents activities of reactive oxygen. Homeostasis is therefore maintained by the balance between d-ROMs and BAP.
As previously stated, living organisms have BAP, which counters d-ROM and increases when the organism is exposed to high d-ROMs levels. However, an organism with physical disorders will eventually run out of BAP and does not function adequately even when d-ROMs levels are increased (Nojima et al.).
All subjects included in the present study were middle-aged women around the age of 50 who were exposed to high d-ROMs. However, given that none of them had any physical disorders, it can be inferred their BAP functioned adequately.
In addition, because d-ROMs were measured during working hours, the increase in d-ROMs could have prevented the increase in BAP as a balancing mechanism to temporarily maintain homeostasis, thereby resulting in decreased BAP levels.
Nonetheless, no significant difference in d-ROMs and BAP, which are indexes for physiological stress, had been found between both care workers and general workers, assuming that they were under similar stress levels.
Significant correlations were found between d-ROMs and weight (r = 0.439) and d-ROMs and BMI (r = 0.382) among care workers and between d-ROMs and weight (r = 0.377) and BAP and BMI (r = −0.359) among general workers.
BMI has been used as a simple index for obesity (Swinburn et al.), while d-ROMs has been generally positively correlated with obesity (Kozuka et al., Suzuki et al., Im et al.). Such findings are reflected in our results wherein d-ROMs were correlated with weight among care workers and general workers and with BMI among care workers, whereas BAP was correlated negatively with BMI among general workers (Table 7). In addition, among general workers, d-ROMs were significantly correlated with awakening time and bedtime, while no such correlation had been observed among care workers (Table 7).
We believe that the absence of a significant correlation between d-ROMs and awakening time and bedtime among care workers was due to their considerably greater lifestyle irregularity compared to general workers. General workers had shorter sleep durations than care workers (Table 7).
Although d-ROMs and BAP showed no significant relationship with health/lifestyle parameters among general workers, a significant relationship was found only between d-ROMs and exercise among care workers. Among 27 subjects, 18 (60%) had d-ROM levels that fell within the "other (mild to very strong)" category and had low exercise parameter scores (Table 8).
The exercise factor consists of two elements: exercise activities/conditions (i.e., enforcement frequency of exercise or sports) and awareness about exercise (i.e., the effect and enjoyment of exercise or sports and the individual's will to start them). The present results suggest that many subjects with high d-ROMs do not get enough exercise or do not expect to benefit from exercise and believe that physiological stress is not related to health or life habits, such as diet and nutrition.
We hypothesized that care workers would experience more health/lifestyle changes and physiological stress than general workers because their irregular working hours and greater physical burden.
However, no significant differences in all health/lifestyle parameters or physiological stress indexes had been found between care workers and general workers, which do not support our hypothesis.
One possible reason could be that the general workers also had poor health, undesirable lifestyles, and high d-ROM levels, similar to care workers. Moreover, as stated previously, BAP levels could have remained low as a mechanism to control the increase in d-ROMs and maintain homeostasis given that d-ROMs were measured during working hours.
Future studies should compare physiological stress during working hours and non-working days between general workers not involved in interpersonal relationship or assistance activities and workers in similar fields as care workers, such as nurses.

Conclusion
Care workers were physically larger and slept longer, probably to recover from fatigue, than general workers. Both groups had high d-ROM levels and normal BAP levels, with no significant difference in terms of either index. Hence, we inferred that both groups were chronically in stressful conditions. Notably, general workers were judged to have poor health and undesirable lifestyles, similar to care workers.
Moreover, several care workers with high d-ROM levels tended to not participate in sports or exercise and did not to expect to benefit from them. Because we measured physiological stress marker levels only during working hours to accommodate cooperation by both groups, the increase in d-ROM levels could have prevented the increase in BAP as a balancing mechanism to temporarily maintain homeostasis, thereby resulting in decreased BAP levels.
Measurements of the physical stress markers during holidays would distinguish the stress levels of care workers from those of general workers. In future studies, selecting workers with consistent working times as the general workers may help clarify differences between care workers and general workers. Despite the limitations of this study, we also found no correlation between d-ROM levels and variations in awakening times and bedtimes of care workers. These results may be attributable to their irregular schedules comparison with those of general workers.