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Passive smoking, prepregnancy obesity increase gestational diabetes risk
Pregnant women exposed to secondhand smoke are at an increased risk for developing gestational diabetes vs. women not exposed to passive smoking, and the effects amplify any risk associated with prepregnancy obesity, according to a large Chinese study.
“Our finding, an additive, interactive effect between passive smoking and prepregnancy obesity on [gestational diabetes] risk, is original, with public health implications,” Junhong Leng, MD, PhD, of the department of epidemiology and biostatistics at the School of Public Health, Tianjin Medical University, China, and colleagues wrote. “In China, the smoking rate was very low in women but very high in men, which put women at high health risk due to passive smoking. While active smoking was associated with increased risk for [gestational diabetes] in Chinese and non-Chinese women, our group is the first to report that passive smoking significantly increased the risk of [gestational diabetes] in a population-based cohort.”
Lend and colleagues analyzed data from 12,786 Chinese women who underwent a 50-g, 1-hour oral glucose tolerance test between 24 and 28 weeks’ gestation; patients underwent a 75-g, 2-hour OGTT if the first test result was at least 7.8 mmol/L (mean age, 29 years; 6.5% with obesity). Patients self-reported passive smoking during pregnancy via questionnaire. Researchers used logistic regression analysis to determine ORs for gestational diabetes risk and estimated any additive interaction between maternal obesity and passive smoking using relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP) and synergy index.
Within the cohort, 8,831 women (65.2%) were exposed to passive smoking during pregnancy; 7.8% of those women developed gestational diabetes vs. 6.3% of women not exposed to passive smoking (P = .002). After adjustment for multiple factors, including maternal age, height, family history of diabetes, parity, Han ethnicity, multiple pregnancies and weight gain, researchers found that pregnant women exposed to passive smoking had an OR of 1.29 for developing gestational diabetes (95% CI, 1.11-1.5). The OR increased for women who were both obese and exposed to passive smoking vs. women who were not obese and not exposed to passive smoking (adjusted OR = 3.09; 95% CI, 2.38-4.02), according to researchers, who also observed an additive interaction (P for RERI and AP < .05).
“Our data show that in Tianjin, China, 35.7% of gestational diabetes cases were attributable to co-exposure to the two risk factors, passive smoking and obesity,” study researcher Xilin Yang, PhD, professor and head of the department of epidemiology and biostatistics at Tianjin Medical University School of Public Health, told Endocrine Today. “Removal of exposure to either passive smoking or obesity or both is expected to result in a large reduction in the chance of development of gestational diabetes.” – by Regina Schaffer
For more information:
Xilin Yang, PhD, can be reached at Tianjin Medical University School of Public Health, Tianjin Medical University, Tianjin 300070, China; email: yangxilin@tmu.edu.cn.
Disclosure: The researchers report no relevant financial disclosures.