ストレスによる免疫抑制とがんの発症に関する前向きコホート研究(シンポジウム : 心身医学における研究と診療の最先端,2007年,第48回日本心身医学会総会(福岡))  [in Japanese] Immunity and Psychosocial Factors as Cancer Risks in a Middle Aged Population(Symposium : Frontiers Research and Practice in Psychosomatic Medicine)  [in Japanese]

抑うつががん発症のリスクファクターであるという報告は多い.NK(natural killer)活性の低下は心理社会的ストレスと関連しており,同時に,がんの発症のリスクファクターであることが知られている.われわれは中年期の就労者集団にて前向きコホート研究を組み,がん発症と,免疫機能,心理社会的要因の関連を調査した.18〜60歳までの3,790人の就労者から,インフォームドコンセントを取り,1997年4月から7年間,上記の目的で追跡を行った.リンパ球サブセットは全参加者から測定し,うち,247人についてNK活性とサイトカイン産生を測定した.性別,年齢,喫煙,アルコール消費量,婚姻状況,教育歴,BMI(body mass index),運動量,がんの家族歴を共変量として用いた.コックス回帰分析により,CD4+CD45RO+メモリーT細胞数と,抑うつ,自尊感情の低さが,がんのリスクファクターであった.本稿においては,その他の心理社会的要因と発がんに関する研究の概観も記載する.

Increased cancer risks are associated with immune suppression and psychosocial factors such as depressive symptoms. Reduced NK cell activity is correlated with psychosocial stresses in cross sectional studies and with increased cancer risks in prospective cohort studies. We have conducted a prospective cohort study in middle aged individuals to elucidate relationships between cancer, immune function and psychosocial factors. Data were obtained from a cohort of 3790 workers, aged 18 to 60 years, beginning in April 1997. At baseline, we measured lymphocyte subpopulations for all participants, and assayed cytokines and NK cytotoxicity for 247 participants. During a 7-year follow-up of this cohort, we identified new cancer cases and attempted to correlate cancer with immune system and psychosocial parameters. After controlling for sex, age, cigarette smoking, alcohol consumption, marital status, education, body mass index (BMI), physical activity and family history of cancer, the hazard ratio of cancer incidence, relative to the number of memory CD4 + CD45RO+T subpopulations were around 8.0. We have also shown that depressive symptoms increased cancer risk via reduced NK cell activity and Th2 shift (adjusted HR=2.67) and that low self esteem increased cancer risk via reduced NK cell activity (adjusted HR=2.22). Increased cancer risks were found in subjects with reduced immune system function, depressive symptoms and low self esteem. I also reviewed the literatures on the relationship between stress and cancer incidence in this article.