Relationships between Lifestyle‐Related Factors and Immune Parameters in Middle‐Aged Male Workers

Relationships between Lifestyle‐Related Factors and Immune Parameters in Middle‐Aged Male Workers: Yumiko Nakano et al. Division of Industrial Health, Osaka Prefectural Institute of Public Health—Recent studies have demonstrated that unhealthy lifestyles and stress act as risk factors for various cardiovascular diseases, cerebrovascular disorders and cancer. The present study was carried out to investigate the effect of individual lifestyle and comprehensive lifestyle practices on T cell function in peripheral blood lymphocytes in 291 middle‐aged male workers belonged to 4 occupational groups: self employed men (I), employees of a television station (II), local civil servants (III) and workers in a manufacturing factory (IV). The proliferative responsiveness of the lymphocytes to phytohemagglutinin (PHA) was measured by the incorporation of radiolabeled thymidine by stimulated lymphocytes in vitro. lnterferonγ(IFNγ T helper type 1 cytokine) and interleukin‐4 (IL‐4; T helper type 2 cytokine) production from the stimulated lymphocytes were measured by quantitative sandwich enzyme immunoassay. Interviews by means of questionnaires including 19 items related to lifestyles, work stress, life event and health condition were performed. Subjects were classified into groups reporting healthy and unhealthy lifestyles according to their responses to the individual questionnaire. Then, the relationships between these lifestyle practices and the immune parameters were analyzed at the level of the occupational groups and the pooled subjects. The average number of unhealthy practices differed significantly among occupational groups, i.e., higher in the order of I, II, III and IV. Significantly negative correlations were observed between the number of unhealthy lifestyle practices and the PHA responses both at the level of the occupational groups and the pooled subjects. In contrast, there was no significant difference in IFN‐y production among occupational groups, though the group I showed a somewhat low tendency. The levels of IL‐4 in group I were noticeably higher than that in the other groups. It may be possible that severe suppression of cell‐mediated immunity changes the balance of T cell subsets from T helper type 1 to T helper type 2. For each lifestyle practice, subjects reporting “healthy” practices on 7 items showed significantly greater proliferative response to PHA than those reporting unhealthy practices. Subjects reporting “healthy” practices on two items showed significantly lower levels of IL‐4 compared with those reporting unhealthy practices. A 1.5‐yr follow up study performed in the subjects with low PHA responses showed that the reduction of unhealthy lifestyle practices significantly improved the PHA responses. Consequently, the present study suggests that the individual unhealthy lifestyle practices may act on the immune system cumulatively, and the measurement of PHA response may be used to evaluate the lifestyle practices of middle‐aged male workers at both the individual and the occupational group level.