Objective The biological effects of selenium have two sides. Proper intake of selenium maintains nutrient metabolism and visual functon of eyes, but insufcient or excessive intake results in visual dysfuncton. Studies have found that insufcient intake of selenium increases the risk of shortsightedness, but there are few reports on the effects of excessive selenium intake on shortsightedness. This study is designed to investgate the relatonship of eyesight with selenium levels in blood, urine, and hair, as well as serum selenoprotein P (SEPP-1) level in populatons with proper and excessive intake of selenium.
Methods A cross-sectonal study was used to select residents living in Enshi of Hubei Province with a high soil selenium level (exposed group) and Xiantao of Hubei Province with normal soil selenium level (control group). According to the principle of cluster random sampling and the inclusion criteria, the study fnally recruited 303 subjects, including 154 residents in the exposed group and 149 residents in the control group. The basic informaton of subjects were collected through questionnaire. Eyesight was detected with international standard visual acuity chart. Blood, urine, and hair samples were collected to measure respectve selenium levels and serum SEPP-1 level. The eyesight and selenium load were compared between the exposed and control groups. Binary logistc regression analysis was applied to explore the relatonships of selenium in blood, urine, and hair and serum SEPP-1 with eyesight.
Results The selenium levels in blood, urine, and hair in the exposed group were signifcantly higher than those in the control group (P < 0.05), but the serum SEPP-1 level was signifcantly lower (P < 0.05). There was a signifcant difference in the distributon of blood selenium grades between the two groups (Z=-11.42, P < 0.05). The results of visual acuity test showed that there were 40 cases with shortsightedness out of 149 subjects (26.8%) in the control group and 80 cases with shortsightedness out of 154 subjects (51.9%) in the exposed group, and the rate of shortsightedness in the exposed group was higher than that in the control group (P < 0.001). The levels of selenium in blood, urine, and hair were moderately correlated between each other (0.4 < r < 0.7, P < 0.001), but had no signifcant relatonship with the level of serum SEEP-1 (P>0.05). The levels of selenium in blood, urine, hair were signifcantly higher in the shortsightedness group than those in the normal eyesight group (P < 0.01). Moreover, there was a signifcant difference in the distributons of selenium in blood, urine, and hair among different eyesight grades, and the selenium levels increased with the severity of eyesight impairment (r values were 0.207, 0.160, and 0.171, and P values were < 0.001, 0.006, and 0.003, respectvely). The binary logistc regression analysis results turned out that the risk of shortsightedness was higher with the increase of the levels of selenium in blood, urine, and hair (ORs were 7.838, 2.431, and 6.896, and 95%CIs were 2.533-24.252, 1.148-5.146, and 2.080-22.831 respectvely) afer adjustng for factors such as sex, age, educaton level, body mass index, smoking, and drinking.
Conclusion High selenium load will increase the risk of shortsightedness, and higher selenium load is associated with more severe eyesight impairment.
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