Original articleAssociations of ikigai as a positive psychological factor with all-cause mortality and cause-specific mortality among middle-aged and elderly Japanese people: Findings from the Japan Collaborative Cohort Study☆
Introduction
Negative psychological factors, such as depression, anxiety, hopelessness, psychological stress, and psychological distress, are associated with increased risks of coronary heart disease [1], [2], [3], [4], [5] and cerebrovascular disease [6], [7], [8]. Recently, there is growing evidence that positive psychological factors are associated with greater longevity, reduced risk of cardiovascular disease, and reduced risk of physical disability [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19].
In this study, we focused on ikigai as a psychological factor that might be associated with all-cause mortality and cause-specific mortality. Ikigai is a Japanese word that is believed to be an important factor for achieving better health and a fulfilling life [20]. Ikigai is defined in Japanese dictionaries as something to live for, the joy and goal of living, a life worth living, and the happiness and benefit of being alive. It is also understood to be a comprehensive concept including not only pleasure and happiness but also the meaning of one's life and self-realization. Although there is no term fully comparable to ikigai in English [21], we considered that the concept of ikigai is similar to both hedonic and eudaimonic views of well-being; a hedonic view defines well-being in terms of pleasure attainment and pain avoidance, and a eudaimonic view defines well-being in terms of degree to which a person is fully functioning [22]. Therefore, ikigai may play an important role in health-related outcomes as well as other positive psychological factors.
Recently, some prospective studies in Japan have shown that the absence of ikigai was associated with an increased risk for all-cause mortality [23], [24], [25], [26]. However, age-, sex-, and/or cause-specific mortality risks were not estimated in most of those studies because of a relatively small study population in a certain area and a short follow-up period. The purpose of this study was to determine whether presence of ikigai is associated with decreased risks for all-cause and cause-specific mortality among middle-aged and elderly Japanese men and women, using data from the Japan Collaborative Cohort (JACC) Study, which has a larger study population and a longer follow-up period than those in previous studies.
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Materials and methods
Data used for this study were obtained from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC study), a nationwide multicenter collaborative study sponsored by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (Monbukagakusho). The methods used in the JACC study have been described in detail elsewhere [27], [28]. Briefly, a baseline survey was conducted between 1988 and 1990, enrolling 127,477 apparently healthy subjects living in 45 areas
Results
During the follow-up period (average, 12.5 years; total of 918,644 person-years), a total of 10,021 deaths (5855 men and 4166 women) were recorded. The causes of death included cancer in 2376 cases, cardiovascular disease in 1599 cases (coronary heart disease in 356 cases, cerebrovascular diseases in 724 cases), and external causes in 430 cases in men. The corresponding numbers of deaths in women were 1421, 1405 (273, 648), and 331, respectively.
Table 1 shows selected baseline characteristics
Discussion
We demonstrated that the presence of ikigai contributed to a reduction of risk for mortality from all causes among middle-aged and elderly Japanese men and women. For cardiovascular mortality, men with ikigai had a significantly lower risk and women with ikigai tended to have a lower risk than those without ikigai. We also showed that mortality risks for cerebrovascular disease and coronary heart disease tended to be lower among men and women with ikigai than among those without ikigai.
Acknowledgments
The authors express their appreciation to Dr. Kunio Aoki, Professor Emeritus, Nagoya University School of Medicine and the former chairman of the JACC study Group, and Dr. Haruo Sugano, the former Director of the Cancer Institute of the Japanese Foundation for Cancer Research, who greatly contributed to initiating the study, and Dr. Yoshiyuki Ohno, Professor Emeritus, Nagoya University School of Medicine, who was the past chairman of the study. The authors also wish to thank Dr. Akizumi
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The JACC Study has been supported by Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan (nos. 61010076, 62010074, 63010074, 1010068, 2151065, 3151064, 4151063, 5151069, 6279102, 11181101, 17015022, 18014011).