Shift work and autoimmune thyroid disorders.

Stress induces autoimmune disorders by affecting the immune response modulation. Recent studies have shown that shift work stress may enhance the onset of the autoimmune Graves hyperthyroidism. On the other hand, the possible association between occupational stress and autoimmune hypothyroidism has not yet been investigated. In order to detect the possible association between shift work and subclinical autoimmune hypothyroidism we investigated the prevalence of isolated anti-peroxidase thyroid (TPO) autoantibodies in 220 shift workers and in 422 day-time workers. Subclinical autoimmune hypothyroidism was diagnosed by the concomitant presence of high anti-TPO values and TSH levels higher than 2.51 mU/l. Anti TPO antibodies were measured by chemiluminescent technology (Advia Centaur) (a value above 60 IU/l was considered altered). Subclinical autoimmune hypothyroidism was diagnosed in 7.7 percent shift workers and in 3.8 percent day-time workers with a statistically significant difference: Odds Ratio (OR) 2.12, 95 percent Confidence Interval (CI) 1.05 to 4.29; p=0.03. The difference persisted after multivariate analysis taking into account age, sex, smoking habits, alcohol intake, familial history of autoimmune thyroid disease and exposure to radiation as possible confounders: OR. 2.24, 95 percent CI.1.01 to 4.94, p 0.05. Altered anti- TPO autoantibodies were found in 13.6 percent shift workers and in 8.6 percent day-time workers OR. 1.64, 95 percent CI.1.03 to 2.74, p=0.05. The significant difference was still detectable after multivariate analysis: OR. 1.95, 95 percent CI. 1.09 to 3.48, p=0.02. Our data show a significant association between shift work and autoimmune hypothyroidism. This finding may have implications in the health surveillance programs.

Follow up study on the immune response to low frequency electromagnetic fields in men and women working in a museum.

Seven women and eight men, exposed to low frequency (50 Hz) electromagnetic fields (EMFs) in a museum for 20 hours a week, were investigated in the years 1999 and 2005. During the first study, the mean EMF exposure in the working place was 1.7 microT and 1.1 microT, respectively. In the first investigation, the EMF-exposed men showed reduced blood NK lymphocytes in relation to controls, while EMF-exposed women presented reduced PHA-stimulated IFN-gamma release from peripheral blood mononuclear cells (PBMC). In the year 2005, blood cytotoxic activity, state and trait anxiety (STAI I and II, respectively) and occupational stress were also investigated. The scores of STAI I and II of the control women were slightly higher than those of the control men. EMF-exposed men showed higher occupational stress but normal immune parameters. EMF-exposed women showed, in relation to controls, lower PHA-stimulated IFN-gamma release from PBMC and reduced blood cytotoxic activity/CD45+-CD16+-56+ NK lymphocytes (but not per ml of blood). One of the women exposed to EMF, who worked a night shift, showed marked lymphopenia with very low NK lymphocytes and reduced IFN-gamma release; these immune parameters returned to normal following a change of work site. This study suggests that low frequency EMFs affect the immune functions of women more than those of men. Moreover, the determination of immune parameters seems to be a useful marker of the health effects of exposure to EMFs.