This study found that the common risk factors of depression in men and women were carbohydrates, cognitive disorder, heart disease and falls, and the pulmonary disease, underweight and educational level (higher and secondary vocational education) were also risk factors for men, including the additional metabolic disease and milk intake for women (6); in terms of protective factors for depression in the older adults, advanced age (men over the age of 85, and women over the age of 75), exercise and social participation were co-protection factors (7), including the additional tea and coffee intake and married status for women. The reasons for the gradual decline in the prevalence rate of depression among the elderly in Taiwan may be related to the social atmosphere that focuses on the health of the elderly in Taiwan in recent years. Under the advocacy of “living happily” and "living happily in old age”, more and more older adults accept the ideas of going on a hike and taking part in more community activities and having exercise to live, for example, singing karaoke at the sodality for the elderly, learning how to make hand-made soaps at community college and climbing mountains, which helps to increase the social participation and exercise of the older adults, especially for the elderly groups, the importance of maintaining good social participation habits for health is comparable to regular exercise and non-smoking. (8) The most common explanation is that social connections provide a cushion against pressure on the elderly and reduce the incidence of pressure-related diseases (9). On the other hand, the parity of high-tech products such as tablets and mobile phones and the popularity of mobile networks have made it easier for the elderly to access information online, have social media accounts such as line and Facebook, maintain ties between the elderly and their relatives and friends through private messages and outgoing messages and other functions and have timely platforms to express their feelings when they feel depressed.
This study found that the prevalence rate of senile depression in women was higher than that in men, which was the same as that in previous studies of each country. In 2002, Kockler, M et al. used Composite International Diagnostic Interview (CIDI) to survey the differences in depression between men and women and also found that women showed more depressive symptomatology than men, in which female elders were prone to taste disturbance or loss of happiness, and male elders are more likely to be accompanied by agitation. (10) Another study of Nolen-Hoeksema et al. explained the differences in the prevalence rate of depression between men and women, first of all, the social status of women is generally inferior to that of men in all cultures of the world due to women’s small strength, so the proportion of women who have experienced trauma and especially sexual abuse in their childhood or prime is higher than that of men, moreover, women continue to experience various forms and objects of harassment, disrespect and disparagement or face economic difficulties while they grow up, so the prevalence rate of depression in women is higher than that in men, regardless of age levels. The study also suggests another more biological reason that the previous studies focused on the direct effects of hormones such as estrogen or progesterone on women's mood, but in fact the mechanisms of association of hormones with depression are not clear, and most of the studies in recent years have turned to the discussions about non-direct effects of female hormone on mood, for example, the regulatory mechanism by which individuals are subjected to pressure. The hypothalamic-pituitary-adrenal (HPA) axis influences mood by regulating various hormones such as cortisol in the body. Dysregulation of HPA response can be found in the groups experiencing major depression, and one of the study’s assumptions about differences in depression in men and women is that women are more likely to experience traumatic events and therefore more likely to experience regulatory disability in HPA response, and it is considered that the causal relationship between the regulatory function of HPA axis and the differences in depression in men and women has not been established, which is one of the feasible directions for future studies. (11) In addition, the causes of higher prevalence rate of depression in women than that in men may also be related to the men’s tendency to be married and have higher proportion of exercise. In the growing environment of the elderly, Taiwan's marriage roles are influenced by the traditional views of valuing the male child only and requiring the woman to stay at home and the man to earn the money in Taiwan, and men are mostly a pillar of the economy and put themselves into the career development in their prime, and their sense of achievement comes from career success; women are often responsible for the internal affairs of the family, including cooking three meals, washing clothes, cleaning and other daily chores, even if they work as a career woman (who also has a job outside), they are mostly the main executor of their household duties after they return home from work. The same results were found in the study of H. C. Hsu, that is, man are generally given a job, and the accumulated connections and social resources at work enable men to have more social participation than women after retirement, which was one of the major causes for helping them maintain their mental health. (12) On the other hand, due to the influence of the concept of “helping the husband and teaching the children”, most of the burdens of educating and bringing up children fall on women. As a result of caring for children from childhood to adulthood and building a deeper connection with children, women are used to worrying about their children's careers, marriage, interpersonal relations and other matters even when they get older. Therefore, women are more likely to worry about whether their children are living well compared with men, which is also a potential factor for the depression in women. In addition to the traditional gender division of labor in society, in terms of daily living habits, men have more exercise than women, and the formation of regular exercise habits help release endorphins and reduce the incidence of depression in men so that women show a higher incidence of depression than men. (13, 14)
This study found that the elders with higher educational level tended to be more likely to show depression than those with lower educational level, which was consistent with the conclusion arrived at by Noori Akhtar-Danesh using Canadian Community Health Survey, Cycle 1.2 (CCHS-1.2) dataset in Ontario, Canada that the degree of depression in the groups with the high school educational level or below was lowest in all categories of educational levels and those with higher educational level had the highest degree of depression. (15) This may be related to the different areas experienced by groups with different educational levels. The elders with higher educational level generally have more to look after and face more complex difficult problems to be addressed than those with lower educational level. The elders with higher educational level may show more consciousness of intellectuals in society, politics, morality and law in addition to their basic living needs, and they are concerned not only with themselves and their families but also with the issues to be considered in more values and ideas. Therefore, the elders with higher educational level consider and worry about a wider range of areas than those with lower educational level. In addition, the occupations and positions of the elders with higher educational level generally tend to labor with minds rather than with body compared with those with lower educational level. Past career failures and crises, if accumulated into old age, may also contribute to the higher prevalence rate of depression among the elders with higher educational level. In addition, the elders who have experienced higher education often have higher self-requirements and higher thresholds for meeting their self-fulfillment needs than those who have not received higher education. If they fail to fulfill their self-expectations or dreams in their prime and perceive their increasingly degraded abilities through everyday chores in their old age, a contrast of having their wish frustrated may upset them and feel dissatisfied with the quality of life for the remainder of their life.
This study found that advanced age is a protective factor for depression, which was different from the previous studies that found that the older adults over the age of 80 suffered from more severe depression than those aged 70–79, indicating that the groups with higher age had higher risk of depression [21]. Demura, Shinichi and others surveyed 657 male elders and 654 female elders living in the community, by using geriatric depression scale (GDS) as the main research method, they found that the old-old elderly showed higher depressive symptoms than the young-old elderly and were more vulnerable to differences in different living habits, while the function of social participation that reduces depression was more effective for the old-old elderly than the young-old elderly [22]. However, in the study of Dan Blazerand others, the duke EPESE (Establishment Of A Population For Epidemiologic Studies Of The Elderly) used the revised version of ces-d to check 3,998 older adults over the age of 65 living in the community, finding that although depressive symptoms were associated with advanced age, women, low income, physical disability and cognitive disorder under bivariate analysis, but under multiple regression analysis, when the above-mentioned risk factors other than age are excluded, the relationship between age and depressive symptoms turns upside down, and the elderly with higher age will have less depressive symptoms. (16) The results show that the elderly with higher age are generally accompanied by the increased risk of physical illness and cognitive disorder. Without excluding other factors, the study found that the groups with higher age had a higher risk of depression. However, if the relationship between advanced age and depression is taken into account in the context of controlling health factors and cognitive disorder, it can be found that advanced age is the most natural protective factor for depression as found in this study. Advanced age has significant protective effect for men over 85 years old and women over 75 years old.
In terms of disease, heart disease is the common risk factor for depression in men and women, metabolic disease is a risk factor for depression in women, and pulmonary disease is a risk factor for depression in men. The findings of heart disease are consistent with other foreign literature. Reiner Rugulies reviewed the literature from 1966 to 2000 on the association of coronary heart disease (CHD) with depression, and analyzed that depression was associated with the development of coronary heart disease in originally healthy individuals [24]. compared with patients without depression, the patients with depression had poor prognosis. The study of Skilton, Michael R and others showed that metabolic disease were associated with the rise in the prevalence rate of depression for men and women, and the higher the values of an individual's metabolic disease, the more severe the degree of depression. (17) With regard to the association between pulmonary disease and depression, a study conducted by Yon Ju Ryu et al in Korea also found the same result. The study took 84 outpatients with chronic obstructive pulmonary disease (COPD), 37 outpatients with asthma, 33 outpatients with bronchitis and 73 healthy persons as the control group, finding that chronic pulmonary disease was associated with depression or anxiety, and depression was particularly evident in the patients with a higher airflow limitation or groups with a history of smoking. (18)
In terms of diet, eating cereals is a common risk factor for depression in men and women, and milk is a risk factor for depression in women, which are important findings of this study. The study of Dragos Inta et al found that the habit of eating low-carbohydrate help improve major depressive disorders (MDD)(19); although no studies have confirmed the exact mechanisms of association of carbohydrate with depression, many studies suspect that it is associated with intestinal symbiotic microbes. Andrew M. Taylor and Hannah D. Holscher reviewed the studies related to key words such as microbes, depression, diet, eating habits, dietary quality, fiber, probiotics... and found that people's mood or depression could be improved by improving dietary quality, for instance, fructooligosaccharide and galactooligosaccharide with the weight of more than 5 grams a day can improve depression, and the amount of bifidobacteria in the body will also become more abundant, and the habit of eating dietary fibers and omega-3-polyunsaturated fatty acids is also considered to be associated with reducing the incidence of depression (20). However, the specific mechanism on how the diet and intestinal symbiotic bacteria affect the degree of depression remains to be further found. Most of the cereals eaten in Asia are rice and millet which are different from barley and wheat varieties used in western countries, whether it has different effects on the degree of depression in the elderly needs to be clarified in more studies in the future. The dietary protection factor is tea and coffee intake, and the study of Xuguang Guo and others found that the group that was accustomed to drinking tea or coffee without sweeteners had a lower prevalence rate of depression than those who did not drink it (21). The same results can be seen in other past studies, for instance, Giuseppe Grosso and others used Embase and PubMed databases to find that groups with higher caffeine intake had only relative risks of 0.76 depression compared with those with lower caffeine intake, with the best protective effect at 400mL per day, and that coffee had a significant effect but tea not. (22) The study of Anu Ruusunen et al also found that coffee helped protect against the occurrence of depression, but tea was irrelevant thereto. (23)
In addition, there are also studies showing that obesity is especially a protective factor for depression in the elderly in Taiwan. For example, the study of Chang, Hung-Hao and others surveyed 1,351 men and 1,165 women and found that about 10.4% of the older men were overweight and 13.4% of them were obese, and that 19.3% of older women were overweight and 26.4% of them were obese, and both the men and women in overweight and obese groups showed a lower depression rate than moderate and underweight groups, which was contrary to western countries. The study found that this situation was related to cultural differences, and overweight and obesity are considered as diseases in the western world, but obesity is regarded as a symbol of wealth and good fortune rather than as a health crisis in Asian countries such as Taiwan (24). The same results were found in the study of Kuo, S-Y et al, and the study used 10-year trajectory patterns of depressive symptoms to survey 445 older adults over the age of 60 between 1989 and 1999, recorded their (CES-D) scale scores and BMI changes over the past ten years and classified the degree of depression in samples into persistent lowness, persistent mildness, recent increase and chronicness, and the groups with persistent depressive symptoms were found to be mainly associated with low BMI.(25)
The limitation of this study is that the sample source is lack of groups living in institutions such as old age care centers, and the physical function and cognitive function of groups usually living in the relevant institutions are worse than those of the elderly living alone and living with relatives, and the proportion of bed rest is higher. Therefore, in this study, the proportion of disability may be underestimated in the absence of samples living in an institution; the questionnaire is the main method of survey, and there may be some differences in the description of questions in the cross-survey data analysis. The answerers may answer different results under different methods of questioning, or there are too many missing values and data registration errors during the interview. The standard for judgement of hearing impairment in the variables is “whether to wear a hearing aid”. Because of economic problems, lack of access channels or maladaptation to aids, many older adults may suffer from hearing impairment but can not use hearing aids in real life so that their number is underestimated.