Among various risk factors, aging is one of the most important factors for the pathogenesis of DED.
1 Consumption of excess calories leads to an acceleration of the aging process, an increase in oxidative stress, and increased incidence of age-related diseases, including cancer and diabetes. Recent advances in our understanding have provided a new way of thinking about interventions in the aging process. Although the aging process is complex, calorie restriction (CR), which refers to a dietary regimen low in calories but without undernutrition, has been known to extend lifespan, as clearly evidenced in various animal species.
8,9 CR profoundly affects the physiologic and pathophysiologic alterations associated with aging and suppresses the incidence of numerous age-related diseases.
10–12 The anti-aging theory, which indicates that DED is a phenotype of the accelerated aging condition of systemic health, is followed throughout Japan.
13 Accordingly, not only systemic diseases (comorbidities) but also predisease conditions, including lifestyle factors, have been investigated in association with DED, and several pioneer works have been published.
14–18
First, several animal studies reported that excess oxidative stress is systemically associated with lacrimal dysfunction
19,20 and CR maintains tear secretion and reduces oxidative stress.
21 Next, the Osaka study, which conducted a cross-sectional study concerning dry eye among office workers, found several new systemic health factors associated with DED, such as metabolic syndrome, low exercise habit, sedentary lifestyle, poor sleep quality, and subjective happiness.
15,17,18 The Osaka Study documented significantly low tear volumes in subjects diagnosed with metabolic syndrome (MetS) and those aged ≥40 years (Fig. 1).
22 MetS is the term for a group of risk factors for diabetes, hypertension, and other lifestyle diseases. It is considered an accelerated aging condition and is related to excessive oxidative stress. Because MetS adversely impacts productivity, more local governments and businesses in Japan are implementing measures to combat this condition. Due to genetic and environmental differences, the obesity rate in Japan is not as high as that in the Western world. However, the Japanese are reported to be more susceptible to damage from MetS than are Europeans or Americans.
23 Moreover, lifestyle changes among the Japanese have increased the prevalence of MetS, primarily in the working-age population. Furthermore, a previous study reported that 73% of those aged ≥60 years have dry eye, indicating a higher incidence of dry eye in the older Japanese population.
24 Taken together, the study shows that aging is an important risk factor for dry eye and MetS may have an influence on the increasing prevalence of dry eye. The finding that MetS is related to DED has been recently confirmed by studies from other countries.
25,26
Moreover, the association between DED and MetS was reinforced by the finding that subjects with DED were found to exercise less.
17 Recent studies reported that, in addition to low levels of physical activity, a prolonged period of sedentary behavior (sitting for instance) is a risk factor for various health problems, including chronic diseases, such as cardiovascular disease, diabetes, and MetS.
27–29 Because physical inactivity and a sedentary life style are detrimental to health, addressing these behaviors has become a global public health priority.
30 The World Health Organization has included a sedentary lifestyle as a new health risk in addition to smoking and obesity. Office workers who were sitting for long hours in front of visual display terminals (VDTs) tended to exhibit sympathetic dominance and suffer from lower back pain and/or painful eyes.
31,32 Eye strain is an important contributor to the development of DED, a disease that has been neglected as a component in the health management of office workers. The results show that a high level of physical activity is associated with a low risk of DED and that sedentary behavior is associated with DED. Tear film breakup time and ocular surface staining scores were significantly associated with International Physical Activity Questionnaire scores; furthermore, tear film breakup time was significantly associated with sedentary time.
17
Furthermore, a statistically significant positive correlation between dry eye symptoms and happiness ratings was found.
18 In other words, subjects with worse dry eye symptoms tended to be less happy. Another finding was poor sleep quality among subjects with dry eye.
16
On the basis of the abovementioned facts and findings that these lifestyle factors associated with DED (in addition to prolonged VDT exposure), we believe that lifestyle intervention, including exercise and an appropriate diet, is a promising treatment strategy for DED. Also, an improvement in lifestyle along with conventional topical treatment was a promising strategy for the management of DED. Thus, strategies for DED management are mainly becoming preventive in nature.
There is clear evidence regarding the benefits of exercise for patients with various systemic diseases, including physical (e.g., DM) and mental (e.g., depression) diseases. Sano et al.
33 reported that exercise increased the secretion of tears in a mouse model of DM. A combination of exercise, diet, and positive thinking has been found to have positive effects on the symptoms of DED.
34,35
Moreover, it has been reported that abdominal breathing reduces the sympathetic nervous system and consequently increases the secretion of tears.
36 It has been reported that work involving the use of VDTs affects heart rate variability and sympathetic nervous activity.
37,38 Abdominal breathing is associated with low levels of sympathetic nervous activity and high levels of parasympathetic nervous activity.
39 The major outcome of this study was the increase in tear meniscus volume due to abdominal breathing. Based on the results of the current study, we suggest that appropriate abdominal breathing may be recommended for the treatment of DED. Especially for VDT users in offices, abdominal breathing can be easily applied to improve the tear meniscus volume.
As other promising systemic interventions, omega 3 and other supplements, including lactoferrin and lactic acid bacteria, have been reported to be effective in the management of DED, especially in VDT loading.
40,41 Because DED is considered to be associated with oxidative stress and inflammation, such dietary foods may have anti-inflammatory or anti-oxidative stress properties against dry eye.
42,43