Association between life-course cigarette smoking and metabolic syndrome: a discovery-replication strategy

Background The relation between cigarette smoking and metabolic syndrome (MetS) remains unclear, and previous studies focusing on MetS are limited in sample size. We investigated the association between life-course smoking and MetS with independent discovery and replication samples. Methods Preliminary analysis utilized data from an annual cross-sectional survey of 15,222 participants aged ≥ 60 years in Tianjin, China. Suggestive associations were followed-up in 8565 adults from the China Health and Nutrition Survey. MetS was identified according to the criteria of the Chinese Diabetes Society in 2013. Life-course smoking was assessed by a comprehensive smoking index (CSI), based on information on smoking intensity, duration, and time since cessation across life-course, collected through standard questionnaires. Participants were divided into four groups: non-smokers; and the tertiles of CSI in ever smokers. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between life-course smoking and MetS. Results In the discovery sample, ORs of MetS were 2.01 (95%CI: 1.64–2.47) and 1.76 (95%CI: 1.44–2.16) for smokers in the highest and second tertile of CSI compared with never smokers. Potential interaction was shown for age, with increased ORs for MetS associated with smoking limited to individuals who aged < 70 years (Pinteraction = 0.015). We were able to replicate the association between cigarette smoking and MetS in an independent adult sample (second tertile vs. never: OR = 1.30, 95%CI: 1.04–1.63). The interaction of smoking with age was also replicated. Conclusions Life-course cigarette smoking is associated with an increased odds of MetS, especially among individuals who aged < 70 years.

Does weight mediate the effect of smoking on coronary heart disease? Parametric mediational g-formula analysis

Background In settings in which there are time-varying confounders affected by previous exposure and a time-varying mediator, natural direct and indirect effects cannot generally be estimated unbiasedly. In the present study, we estimate interventional direct effect and interventional indirect effect of cigarette smoking as a time-varying exposure on coronary heart disease while considering body weight as a time-varying mediator. Methods To address this problem, the parametric mediational g-formula was proposed to estimate interventional direct effect and interventional indirect effect. We used data from the Multi-Ethnic Study of Atherosclerosis to estimate effect of cigarette smoking on coronary heart disease, considering body weight as time-varying mediator. Results Over a 11-years period, smoking 20 cigarettes per day compared to no smoking directly (not through weight) increased risk of coronary heart disease by an absolute difference of 1.91% (95% CI: 0.49%, 4.14%), and indirectly decreased coronary heart disease risk by -0.02% (95% CI: -0.05%, 0.04%) via change in weight. The total effect was estimated as an absolute 1.89% increase (95% CI: 0.49%, 4.13%). Conclusion The overall absolute impact of smoking to incident coronary heart disease is modest, and we did not discern any important contribution to this effect relayed through changes to bodyweight. In fact, changes in weight because of smoking have no meaningful mediating effect on CHD risk.

Educational attainment, health outcomes and mortality: a within-sibship Mendelian randomization study

Previous Mendelian randomization (MR) studies using population samples (population-MR) have provided evidence for beneficial effects of educational attainment on health outcomes in adulthood. However, estimates from these studies may have been susceptible to bias from population stratification, assortative mating and indirect genetic effects due to unadjusted parental genotypes. Mendelian randomization using genetic association estimates derived from within-sibship models (within-sibship MR) can avoid these potential biases because genetic differences between siblings are due to random segregation at meiosis. Applying both population and within-sibship MR, we estimated the effects of genetic liability to educational attainment on body mass index (BMI), cigarette smoking, systolic blood pressure (SBP) and all-cause mortality. MR analyses used individual-level data on 72,932 siblings from UK Biobank and the Norwegian HUNT study and summary-level data from a within-sibship Genome-wide Association Study including over 140,000 individuals. Both population and within-sibship MR estimates provided evidence that educational attainment influences BMI, cigarette smoking and SBP. Genetic variant-outcome associations attenuated in the within-sibship model, but genetic variant-educational attainment associations also attenuated to a similar extent. Thus, within-sibship and population MR estimates were largely consistent. The within-sibship MR estimate of education on mortality was imprecise but consistent with a putative effect. These results provide evidence of beneficial individual-level effects of education (or liability to education) on adulthood health, independent of potential demographic and family-level confounders.

Maternal cigarette smoking before or during pregnancy increases the risk of birth congenital anomalies: a population-based retrospective cohort study of 12 million mother-infant pairs

Background The associations of maternal cigarette smoking with congenital anomalies in offspring have been inconsistent. This study aimed to clarify the associations of the timing and intensity of maternal cigarette smoking with 12 subtypes of birth congenital anomalies based on a nationwide large birth cohort in the USA. Methods We used nationwide birth certificate data from the US National Vital Statistics System during 2016–2019. Women reported the average daily number of cigarettes they consumed 3 months before pregnancy and in each subsequent trimester during pregnancy. Twelve subtypes of congenital anomalies were identified in medical records. Poisson regression analysis was used to estimate the risk ratios (RRs) with 95% confidence intervals (CIs) for 12 subtypes of congenital anomalies associated with the timing (i.e., before pregnancy, and during three different trimesters of pregnancy) and intensity (i.e., number of cigarettes consumed per day) of maternal cigarette smoking. Results Among the 12,144,972 women included, 9.3% smoked before pregnancy and 7.0%, 6.0%, and 5.7% in the first, second, and third trimester, respectively. Maternal smoking before or during pregnancy significantly increased the risk of six subtypes of birth congenital anomalies (i.e., congenital diaphragmatic hernia, gastroschisis, limb reduction defect, cleft lip with or without cleft palate, cleft palate alone, and hypospadias), even as low as 1–5 cigarettes per day. The adjusted RRs (95% CIs) for overall birth congenital anomalies (defined as having any one of the congenital malformations above significantly associated with maternal cigarette smoking) among women who smoked 1–5, 6–10, and ≥ 11 cigarettes per day before pregnancy were 1.31 (1.22–1.41), 1.25 (1.17–1.33), and 1.35 (1.28–1.43), respectively. Corresponding values were 1.23 (1.14–1.33), 1.33 (1.24–1.42), 1.33 (1.23–1.43), respectively, for women who smoked cigarettes in the first trimester; 1.32 (1.21–1.44), 1.36 (1.26–1.47), and 1.38 (1.23–1.54), respectively, for women who smoked cigarettes in the second trimester; and 1.33 (1.22–1.44), 1.35 (1.24–1.47), and 1.35 (1.19–1.52), respectively, for women who smoked cigarettes in the third trimester. Compared with women who kept smoking before and throughout pregnancy, women who never smoked had significantly lower risk of congenital anomalies (RR 0.77, 95% CI 0.73–0.81), but women who smoked before pregnancy and quitted during each trimester of pregnancy had no reduced risk (all P > 0.05). Conclusions Maternal smoking before or during pregnancy increased the risk of several birth congenital anomalies, even as low as 1–5 cigarettes per day. Maternal smokers who stopped smoking in the subsequent trimesters of pregnancy were still at an increased risk of birth congenital anomalies. Our findings highlighted that smoking cessation interventions should be implemented before pregnancy.

Association of Acute Postoperative Pain and Cigarette Smoking With Cerebrospinal Fluid Levels of Beta-Endorphin and Substance P

Objectives: Cigarette smoking is associated with postoperative pain perception, which might be mediated by beta-endorphin and substance P. These effects on postoperative pain perception have never been investigated in human cerebrospinal fluid (CSF), which reflects biochemical alterations in the brain. Therefore, we investigated the associations among cigarette smoking, postoperative pain, and levels of beta-endorphin and substance P in human CSF.Methods: We recruited 160 Chinese men (80 active smokers and 80 nonsmokers) who underwent lumbar puncture before anterior cruciate ligament reconstruction, and 5-ml CSF samples were collected. Pain visual analog scale (VAS) scores, post-anesthetic recovery duration (PARD), and smoking variables were obtained. CSF levels of beta-endorphin and substance P were measured.Results: Compared to non-smokers, active smokers had significantly higher pain VAS (2.40 ± 0.67 vs. 1.70 ± 0.86, p &lt; 0.001) and PARD scores (9.13 ± 2.11 vs. 7.27 ± 1.35, p = 0.001), lower CSF beta-endorphin (33.76 ± 1.77 vs. 35.66 ± 2.20, p = 0.001) and higher CSF substance P (2,124.46 ± 217.34 vs. 1,817.65 ± 302.14, p &lt; 0.001) levels. Pain VAS scores correlated with PARD in active smokers (r = 0.443, p = 0.001).Conclusions: Cigarette smoking is associated with increased postoperative pain intensity, shown by delayed pain perception, higher pain VAS scores, and lower beta-endorphin and higher substance P levels in the CSF of active smokers. The more extended postoperative pain perception is delayed, the more pain intensity increases.

Tobacco Consumption and High‐Sensitivity Cardiac Troponin I in the General Population: The HUNT Study

Background Cardiac troponins represent a sensitive index of subclinical myocardial injury and are associated with increased risk of cardiovascular events in the general population. Despite positive associations with cardiovascular risk of both cardiac troponins and cigarette smoking, concentrations of cardiac troponin I measured by high‐sensitivity assays (hs‐cTnI) are paradoxically lower in current smokers than in never‐smokers. The impact of smoking intensity and time from smoking cessation on hs‐cTnI remains unknown. Methods and Results hs‐cTnI concentrations were measured in 32028 subjects free from cardiovascular disease enrolled in the prospective, population‐based HUNT (Trøndelag Health Study). Tobacco habits were self‐reported and classified as never (n=14 559), former (n=14 248), and current (n=3221) smokers. Current smokers exhibited significantly lower concentrations of hs‐cTnI than never‐smokers ( P <0.001). In adjusted models, both current smoking (−17.3%; 95% CI, −20.6 to −13.9%) and former smoking (−6.6%; 95% CI, −8.7 to −4.5%) were associated with significantly lower hs‐cTnI concentrations. Among former smokers, higher smoking burden (>10 pack‐years) were associated with lower concentrations of hs‐cTnI. Time since smoking cessation was associated with increasing concentrations of hs‐cTnI in a dose‐dependent manner ( P for trend<0.001), and subjects who quit smoking >30 years ago had concentrations of hs‐cTnI comparable with those of never‐smokers. Conclusions In the general population, both current and former cigarette smoking is associated with lower concentrations of hs‐cTnI. In former smokers, there was a dose‐response relationship between pack‐years of smoking, and hs‐cTnI. Time since smoking cessation was associated with increasing concentrations of hs‐cTnI, indicating a continuum of hs‐cTnI from current smoker to never‐smokers.