Psychological attitudes and risk of breast cancer in Japan: a prospective study.
OBJECTIVE
To examine the association between psychological factors and the risk of breast cancer prospectively in a non-Western population.


METHODS
Data from the Japan Collaborative Cohort (JACC) study were analyzed. From 1988 to 1990, 34,497 women aged 40-79 years completed a questionnaire on medical, lifestyle and psychosocial factors. The rate ratios (RRs) of their responses were computed by fitting to proportional hazards models.


RESULTS
During the mean follow-up period of 7.5 years, 149 breast cancer cases were documented. Those individuals who possessed "ikigai" (Japanese term meaning something that made one's life worth living) showed a significantly lower risk of breast cancer (multivariate-adjusted RR=0.66; 95% confidence interval [CI]=0.47-0.94). Those who perceived themselves as able to make decisions quickly also had a lower risk of breast cancer (multivariate-adjusted RR=0.56; 95% CI=0.36-0.87). The other factors investigated, including ease of anger arousal and self-perceived stress of daily life were not associated with breast cancer risk.


CONCLUSIONS
Although further studies will be necessary to verify these findings, our results suggest that having "ikigai" and being decisive decrease an individual's subsequent risk of breast cancer.
Wakai
Kenji
K
Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya, 464-8681, Japan. wakai@med.nagoya-u.ac.jp
Kojima
Masayo
M
Nishio
Kazuko
K
Suzuki
Sadao
S
Niwa
Yoshimitsu
Y
Lin
Yingsong
Y
Kondo
Takaaki
T
Yatsuya
Hiroshi
H
Tamakoshi
Koji
K
Yamamoto
Akio
A
Tokudome
Shinkan
S
Toyoshima
Hideaki
H
Tamakoshi
Akiko
A
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000523:psychology*; D003657:Decision Making; D005260:Female; D006801:Humans; D007564:Japan; D008875:Middle Aged; D010549:Personal Satisfaction; D012307:Risk Factors; D013315:Stress, Psychological; D011795:Surveys and Questionnaires; D013694:Temperament