A brief exposure to moderate passive smoke increases metabolism and thyroid hormone secretion

Abstract

Context: Active smoking influences normal metabolic status and thyroid function. Objective: The objective was to assess experimentally the effects of 1 h of moderate passive smoking in a controlled simulated bar/ restaurant environment on the metabolism and thyroid hormone levels in healthy nonsmokers. Participants: Eighteen ( nine females, nine males) healthy individuals ( mean +/- SD: age, 25.3 +/- 3.1 yr; height, 174.0 +/- 10.1 cm; weight, 65.2 +/- 13.7 kg) participated in the study. Design: In repeated- measures randomized blocks, participants visited the laboratory on 2 consecutive days. In the experimental condition, they were exposed to 1 h of moderate passive smoking at a carbon monoxide concentration of 23 +/- 1 ppm in an environmental chamber, whereas in the control condition participants remained in the same chamber for 1 h breathing normal atmospheric air. Main Outcome Measures: In both conditions, cotinine serum and urine levels, resting energy expenditure ( REE), as well as concentration of T(3), free T(4), and TSH were assessed before participants entered the chamber and immediately after their exit. Heart rate and blood pressure were tested in 10-min intervals during all REE assessments. Results: The mean +/- SD difference of serum and urine cotinine levels ( - 0.27 +/- 3.94 vs. 14.01 +/- 6.54 and 0.05 +/- 2.07 vs. 7.23 +/- 3.75, respectively), REE ( 6.73 +/- 98.06 vs. 80.58 +/- 120.91) as well as T3 and free T(4) ( 0.05 +/- 0.11 vs. 0.13 +/- 0.12 and 0.02 +/- 0.15 vs. 0.22 +/- 0.20) were increased in the experimental compared with the control condition at baseline and follow- up ( P < 0.05). No statistically significant variation was observed in the mean difference of the remaining parameters ( P > 0.05). Serum and urine cotinine values were linearly associated with REE ( P < 0.05). Conclusion: One hour of passive smoking at bar/ restaurant levels is accompanied by significant increases in metabolism and thyroid hormone levels.