Heavier smoking may lead to a relative increase in waist circumference: evidence for a causal relationship from a Mendelian randomisation meta-analysis. The CARTA consortium

Association of cigarette smoking with cardiometabolic risk factors: A cross-sectional study

INTRODUCTION

Despite strong and consistent epidemiological evidence linking cigarette smoking to several cardiovascular diseases (CVDs), the association between smoking intensity and CVD risk factors remains unclear. This study aimed to explore the possible effects of cigarette smoking on cardiometabolic risk in healthy individuals.

METHODS

This cross-sectional study was conducted between November 2022 and June 2023. Consecutive sampling was performed to include 160 healthy participants: 100 smokers with 60 males and 40 females; and 60 age- and sex-matched non-smokers with 36 males and 24 females. Blood samples were taken from each participant to assess their cardiometabolic function: lipid profile, von Willebrand factor (vWF), high-sensitivity cardiac troponin I (hs-cTnI), and fibrinogen levels; and liver function using an automated enzymatic method. In addition, blood sugar level, body mass index (BMI), and blood pressure were recorded.

RESULTS

Smokers had significantly higher vWF functional activity and hs-cTnI but significantly lower albumin and total bilirubin levels than non-smokers (65.87 ± 19.07 vs 56.45 ± 6.59, respectively, p<0.001; 0.0382 ± 0.0077 vs 0.0147 ± 0.0105, respectively, p<0.001; and 4.63 ± 0.32 vs 4.74 ± 0.28, respectively, p=0.026). The number of cigarettes consumed daily was associated positively and significantly with plasma levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, vWF functional activity, and hs-cTnI but were negatively associated with total bilirubin. Moreover, heavy smokers had a significantly higher BMI and waist-to-hip ratio among male smokers than non-smokers.

CONCLUSIONS

Cigarette smoking was associated with increased dyslipidemia, BMI, and central obesity, in addition to higher vWF functional activity. Altogether, increased hs-cTnI levels in smokers indicate a higher susceptibility to CVD.

Estimating causality between smoking and abdominal obesity by Mendelian randomization

BACKGROUND AND AIMS

Smokers tend to have a lower body weight than non-smokers, but also more abdominal fat. It remains unclear whether or not the relationship between smoking and abdominal obesity is causal. Previous Mendelian randomization (MR) studies have investigated this relationship by relying upon a single genetic variant for smoking heaviness. This approach is sensitive to pleiotropic effects and may produce imprecise causal estimates. We aimed to estimate causality between smoking and abdominal obesity using multiple genetic instruments.

DESIGN

MR study using causal analysis using summary effect estimates (CAUSE) and latent heritable confounder MR (LHC-MR) methods that instrument smoking using genome-wide data, and also two-sample MR (2SMR) methods.

SETTING

Genome-wide association studies (GWAS) summary statistics from participants of European ancestry, obtained from the GWAS and Sequencing Consortium of Alcohol and Nicotine use (GSCAN), Genetic Investigation of Anthropometric Traits (GIANT) Consortium and the UK Biobank.

PARTICIPANTS

We used GWAS results for smoking initiation (n = 1 232 091), life-time smoking (n = 462 690) and smoking heaviness (n = 337 334) as exposure traits, and waist-hip ratio (WHR) and waist and hip circumferences (WC and HC) (n up to 697 734), with and without adjustment for body mass index (adjBMI), as outcome traits.

MEASUREMENTS

Smoking initiation, life-time smoking, smoking heaviness, WHR, WC, HC, WHRadjBMI, WCadjBMI and HCadjBMI.

FINDINGS

Both CAUSE and LHC-MR indicated a positive causal effect of smoking initiation on WHR (0.13 [95% confidence interval (CI) = 0.10, 0.16 and 0.49 (0.41, 0.57), respectively] and WHRadjBMI (0.07 (0.03, 0.10) and 0.31 (0.26, 0.37). Similarly, they indicated a positive causal effect of life-time smoking on WHR [0.35 (0.29, 0.41) and 0.44 (0.38, 0.51)] and WHRadjBMI [0.18 (0.13, 0.24) and 0.26 (0.20, 0.31)]. In follow-up analyses, smoking particularly increased visceral fat. There was no evidence of a mediating role by cortisol or sex hormones.

CONCLUSIONS

Smoking initiation and higher life-time smoking may lead to increased abdominal fat distribution. The increase in abdominal fat due to smoking is characterized by an increase in visceral fat. Thus, efforts to prevent and cease smoking can have the added benefit of reducing abdominal fat.

Association of serum leptin and ghrelin levels with smoking status on body weight: a systematic review and meta-analysis

Background and aims

Smoking cigarettes is a major global health problem that affects appetite and weight. The aim of this systematic review was to determine how smoking affected plasma leptin and ghrelin levels.

Methods

A comprehensive search of PubMed, Scopus, Web of Science, and Ovid was conducted using a well-established methodology to gather all related publications.

Results

A total of 40 studies were included in the analysis of 11,336 patients. The overall effect showed a with a mean difference (MD) of -1.92[95%CI; -2.63: -1.20] and p = 0.00001. Subgroup analysis by study design revealed significant differences as well, but with high heterogeneity within the subgroups (I2 of 82.3%). Subgroup by sex showed that there was a significant difference in mean difference between the smoking and non-smoking groups for males (MD = -5.75[95% CI; -8.73: -2.77], p = 0.0002) but not for females (MD = -3.04[95% CI; -6.6:0.54], p = 0.10). Healthy, pregnant, diabetic and CVD subgroups found significant differences in the healthy (MD = -1.74[95% CI; -03.13: -0.35], p = 0.01) and diabetic (MD = -7.69[95% CI, -1.64: -0.73], p = 0.03). subgroups, but not in the pregnant or cardiovascular disease subgroups. On the other hand, the meta-analysis found no statistically significant difference in Ghrelin serum concentration between smokers and non-smokers (MD = 0.52[95% CI, -0.60:1.63], p = 0.36) and observed heterogeneity in the studies (I2 = 68%).

Conclusion

This study demonstrates a correlation between smoking and serum leptin/ghrelin levels, which explains smoking's effect on body weight.

Systematic review registration

https://www.crd.york.ac.uk/ prospero/display_record.php, identifier (Record ID=326680).

Relationship between body fat ratio and inflammatory markers in a Chinese population of adult male smokers

Objective

To explore the correlation between changes in the body fat ratio (BFR) and peripheral blood inflammatory markers according to smoking status in the adult Chinese male population.

Methods

A total of 865 participants (aged 20-70 years) were included. All participants underwent a physical health examination at Xiguzhou Central Hospital between October 2015 and July 2016, including measurements of body mass index (BMI), BFR, white blood cell [WBC] count, and neutrophil-lymphocyte ratio [NLR].

Results

WBCs count and NLR were significantly higher in adult male smokers than in non-smokers (P = 0.00). According to the BFR stratification analysis, WBC count and NLR significantly increased in accordance with BFR (P = 0.00). This finding remained significant after adjusting for relevant confounding factors (P < 0.05). Two-factor stratified analysis of smoking status and BFR showed that WBC count and NLR in the smoking population were higher than in nonsmokers, regardless of BFR. The interaction model showed that BFR and smoking status affected WBC count and NLR changes (P < 0.05). A significant positive correlation was found between WBC count, NLR, and BFR in adult male smokers; however, there was no significant correlation with BMI. There was an interaction between smoking and BFR, both of which synergistically affected changes in inflammatory markers, including WBC count and NLR.

Conclusion

WBC count and NLR of smokers with a high BFR were significantly higher than those of nonsmokers with a low BFR. It is important to provide evidence-based medical evidence for social tobacco control and to reduce BFR.

Central and peripheral actions of nicotine that influence blood glucose homeostasis and the development of diabetes

Cigarette smoking has long been recognized as a risk factor for type 2 diabetes (T2D), although the precise causal mechanisms underlying this relationship remain poorly understood. Recent evidence suggests that nicotine, the primary reinforcing component in tobacco, may play a pivotal role in connecting cigarette smoking and T2D. Extensive research conducted in both humans and animals has demonstrated that nicotine can elevate blood glucose levels, disrupt glucose homeostasis, and induce insulin resistance. The review aims to elucidate the genetic variants of nicotinic acetylcholine receptors associated with diabetes risk and provide a comprehensive overview of the available data on the mechanisms through which nicotine influences blood glucose homeostasis and the development of diabetes. Here we emphasize the central and peripheral actions of nicotine on the release of glucoregulatory hormones, as well as its effects on glucose tolerance and insulin sensitivity. Notably, the central actions of nicotine within the brain, which encompass both insulin-dependent and independent mechanisms, are highlighted as potential targets for intervention strategies in diabetes management.

The Effects of Smoking on the Diagnostic Characteristics of Metabolic Syndrome: A Review

Metabolic syndrome is a growing epidemic that increases the risk for cardiovascular disease, diabetes, stroke, and mortality. It is diagnosed by the presence of three or more of the following risk factors: 1) obesity, with an emphasis on central adiposity, 2) high blood pressure, 3) hyperglycemia, 4) dyslipidemia, with regard to reduced high-density lipoprotein concentrations, and 5) dyslipidemia, with regard to elevated triglycerides. Smoking is one lifestyle factor that can increase the risk for metabolic syndrome as it has been shown to exert negative effects on abdominal obesity, blood pressure, blood glucose concentrations, and blood lipid profiles. Smoking may also negatively affect other factors that influence glucose and lipid metabolism including lipoprotein lipase, adiponectin, peroxisome proliferator-activated receptors, and tumor necrosis factor-alpha. Some of these smoking-related outcomes may be reversed with smoking cessation, thus reducing the risk for metabolic disease; however, metabolic syndrome risk may initially increase post cessation, possibly due to weight gain. Therefore, these findings warrant the need for more research on the development and efficacy of smoking prevention and cessation programs.

Relationship Between Heart Disease and Obesity Indicators Among Adults: A Secondary Data Analysis

Background Body mass index (BMI), waist circumference (WC), and hip circumference (HC) determine obesity. Several studies have examined the association between obesity and many diseases, including heart disease, and found it to be a substantial risk factor. However, the relationship between heart disease and obesity has not been investigated. This study investigated the relationship between heart disease and obesity indicators among adults encompassing sociodemographic and lifestyle factors. Methodology This cross-sectional study included data from 3,574 individuals who participated in the 2011-2014 National Survey of Midlife Development in the United States refresher. The presence or absence of heart conditions such as irregular heartbeat, heart murmur, heart attack, and heart failure was determined using self-reported questionnaires. The association between heart disease and obesity indicators such as BMI, WC, HC, and waist-to-hip ratio (WHR) was investigated using linear regression. Results After controlling for all factors, the findings demonstrated a significant relationship between heart disease and BMI, WC, and HC high scores of 1.12 kg/m², 0.63 inches, and 0.81 inches, respectively. A higher score in all obesity indicators was linked to being 65 years or older; male gender (for HC); having a school/college level of education; being unmarried, divorced, or widowed; having a history of smoking; and avoiding alcohol use. Conclusions Heart disease and sociodemographic and lifestyle factors are substantially associated with a high score in all obesity indicators. The findings of this study are important because they can assist healthcare providers in implementing different therapies to prevent high BMI, WC, HC, and WHR.

Disentangling the aetiological pathways between body mass index and site-specific cancer risk using tissue-partitioned Mendelian randomisation

BACKGROUND

Body mass index (BMI) is known to influence the risk of various site-specific cancers, however, dissecting which subcomponents of this heterogenous risk factor are predominantly responsible for driving disease effects has proven difficult to establish. We have leveraged tissue-specific gene expression to separate the effects of distinct phenotypes underlying BMI on the risk of seven site-specific cancers.

METHODS

SNP-exposure estimates were weighted in a multivariable Mendelian randomisation analysis by their evidence for colocalization with subcutaneous adipose- and brain-tissue-derived gene expression using a recently developed methodology.

RESULTS

Our results provide evidence that brain-tissue-derived BMI variants are predominantly responsible for driving the genetically predicted effect of BMI on lung cancer (OR: 1.17; 95% CI: 1.01-1.36; P = 0.03). Similar findings were identified when analysing cigarettes per day as an outcome (Beta = 0.44; 95% CI: 0.26-0.61; P = 1.62 × 10-6), highlighting a possible shared aetiology or mediator effect between brain-tissue BMI, smoking and lung cancer. Our results additionally suggest that adipose-tissue-derived BMI variants may predominantly drive the effect of BMI and increased risk for endometrial cancer (OR: 1.71; 95% CI: 1.07-2.74; P = 0.02), highlighting a putatively important role in the aetiology of endometrial cancer.

CONCLUSIONS

The study provides valuable insight into the divergent underlying pathways between BMI and the risk of site-specific cancers.

A fast and powerful linear mixed model approach for genotype-environment interaction tests in large-scale GWAS

Genotype-by-environment interaction (GEI or GxE) plays an important role in understanding complex human traits. However, it is usually challenging to detect GEI signals efficiently and accurately while adjusting for population stratification and sample relatedness in large-scale genome-wide association studies (GWAS). Here we propose a fast and powerful linear mixed model-based approach, fastGWA-GE, to test for GEI effect and G + GxE joint effect. Our extensive simulations show that fastGWA-GE outperforms other existing GEI test methods by controlling genomic inflation better, providing larger power and running hundreds to thousands of times faster. We performed a fastGWA-GE analysis of ~7.27 million variants on 452 249 individuals of European ancestry for 13 quantitative traits and five environment variables in the UK Biobank GWAS data and identified 96 significant signals (72 variants across 57 loci) with GEI test P-values < 1 × 10-9, including 27 novel GEI associations, which highlights the effectiveness of fastGWA-GE in GEI signal discovery in large-scale GWAS.

Prevalence of Cardiovascular Risk Factors in Middle-Aged Lithuanian Men Based on Body Mass Index and Waist Circumference Group Results from the 2006-2016 Lithuanian High Cardiovascular Risk Prevention Program

Background and aims: This study aimed to estimate the prevalence of cardiovascular risk factors in middle-aged Lithuanian men categorized according to body mass index and waist circumference results. Methods and results: The data were from the Lithuanian High Cardiovascular Risk primary prevention program between 2009 and 2016. This community-based cross-sectional study comprised 38,412 men aged 40 to 54 years old. We compared the prevalence of arterial hypertension, dyslipidaemia, diabetes mellitus, smoking, and metabolic syndrome in body mass index (BMI) and waist circumference (WC) groups. Regarding the allometric anthropometrics for WC, A Body Shape Indices (ABSIs) were analyzed with respect to mortality risk and smoking status. The most prevalent risk factor in men was dyslipidaemia, followed by arterial hypertension and smoking (86.96%, 47.94%, and 40.52%, respectively). All risk factors except for smoking were more prevalent in men with overweight or obesity as measured by BMI compared to men with normal weight. Similarly, smoking was the only cardiovascular risk factor that was more prevalent among subjects with normal WC compared to those with increased WC or abdominal obesity. Elevated ABSI, which is associated with higher mortality risk, was more prevalent in smokers. Conclusion: The most prevalent cardiovascular risk factor among middle-aged Lithuanian men was dyslipidaemia, with a surprisingly high prevalence in all BMI and WC groups. Smoking was the only risk factor most prevalent in subjects with low or normal weight according to BMI. It was also more prevalent in the normal WC group compared to the increased WC or abdominal obesity groups, but ABSI values associated with higher mortality were more prevalent among smokers than non-smokers.

Prevalence of smoking (cigarette and waterpipe) and its association with obesity/overweight in UAE and Palestine

Aim

This study aimed to assess the prevalence rate of smoking behavior (cigarette and waterpipe) and its association with obesity/ overweight among university students in the United Arab Emirates (UAE) and Palestine.

Methods

A cross-sectional study was conducted at a convenient sample of 10 largest universities in the West Bank- Palestine and Dubai- UAE. In total, 3800 students were randomly selected from the universities, with an 87.6% response rate. A self-administered questionnaire was used to collect the data. The key measures were: waterpipe smoking, weight, height, cigarette smoking, dieting to reduce weight, and perception and knowledge related to tobacco waterpipe smoking (TWP). Body Mass Index (BMI) was calculated using the WHO cutoffs.

Results

The analysis included 3,327 students (54% from the West Bank and 46% from Dubai). About 16% of students in Dubai and 18% of students in the West Bank smoke cigarettes. Quarter (26%) of the students in Dubai and 32% of the students in West Bank smoke water pipes. 17% of students in Dubai and 18% of students in the West Bank reported that they smoke waterpipes to reduce their weight. Waterpipe smoking was found to have a significant positive association with obesity/overweight (p < 0.001).

Conclusions

Smoking is very common among university students. Waterpipe smoking was associated with obesity. More research is still needed in this field to better understand the relationship between cigarette smoking and obesity.

Association of Physical Activity with Anthropometrics Variables and Health-Related Risks in Healthy Male Smokers

Anthropometric variables (AV) are shown to be essential in assessing health status and to serve as markers for evaluating health-related risks in different populations. Studying the impact of physical activity (PA) on AV and its relationship with smoking is a non-trivial task from a public health perspective. In this study, a total of 107 healthy male smokers (37 ± 9.42 years) were recruited from different states in Malaysia. Standard procedures of measurement of several anthropometric indexes were carried out, and the International Physical Activity Questionnaire (IPPQ) was used to ascertain the PA levels of the participants. A principal component analysis was employed to examine the AV associated with physical activity, k-means clustering was used to group the participants with respect to the PA levels, and discriminant analysis models were utilized to determine the differential variables between the groups. A logistic regression (LR) model was further employed to ascertain the efficacy of the discriminant models in classifying the two smoking groups. Six AV out of twelve were associated with smoking behaviour. Two groups were obtained from the k-means analysis, based on the IPPQ and termed partially physically active smokers (PPAS) or physically nonactive smokers (PNAS). The PNAS were found to be at high risk of contracting cardiovascular problems, as compared with the PPAS. The PPAS cluster was characterized by a desirable AV, as well as a lower level of nicotine compared with the PNAS cluster. The LR model revealed that certain AV are vital for maintaining good health, and a partially active lifestyle could be effective in mitigating the effect of tobacco on health in healthy male smokers.

Genetically Predicted Adiposity, Diabetes, and Lifestyle Factors in Relation to Diverticular Disease

BACKGROUND & AIMS

Adiposity, type 2 diabetes, alcohol and coffee consumption, and smoking have been examined in relation to diverticular disease in observational studies. We conducted a Mendelian randomization study to assess the causality of these associations.

METHODS

Independent genetic instruments associated with the studied exposures at genome-wide significance were obtained from published genome-wide association studies. Summary-level data for the exposure-associated single nucleotide polymorphisms with diverticular disease were available in the FinnGen consortium (10,978 cases and 149,001 noncases) and the UK Biobank study (12,662 cases and 348,532 noncases).

RESULTS

Higher genetically predicted body mass index and genetic liability to type 2 diabetes and smoking initiation were associated with an increased risk of diverticular disease in meta-analyses of results from the two studies. The combined odds ratio of diverticular disease was 1.23 (95% confidence interval [CI], 1.14-1.33; P < .001) for a 1-standard deviation (~4.8 kg/m²) increase in body mass index, 1.04 (95% CI, 1.01-1.07; P = .007) for a 1-unit increase in log-transformed odds ratio of type 2 diabetes, and 1.21 (95% CI, 1.12-1.30; P < .001) for a 1-standard deviation increase in prevalence of smoking initiation. Coffee consumption was not associated with diverticular disease, whereas the association for alcohol consumption largely differed between the 2 studies.

CONCLUSIONS

This study strengthens the causal associations of higher body mass index, type 2 diabetes, and smoking with an increased risk of diverticular disease. Coffee consumption is not associated with diverticular disease. Whether alcohol consumption affects the risk of diverticular disease needs further investigation.

Prevalence of general and abdominal obesity and its relationship with opium, total opiate drugs, and chronic smoking: Fasa cohort study

BACKGROUND AND AIMS

Obesity and drug use are two major global issues today. This study aimed to evaluate the relationship between alcohol and tobacco use with general and central obesity.

METHODS

The data of the longitudinal population-based study were collected from the basis of the Fasa Cohort Study (FACS). Participants were 10141 people with 35-70 years old. Data were analyzed by SPSS 20 software. Binary logistic regression (BLR) was used for modelling. A significance level (α) less than 0.05% was considered for hypothesis testing.

RESULTS

Of the total participants (N = 10104), 54.8% (n = 5539) were women. The prevalence of central obesity in terms of waist circumference (WC), waist to hip ratio (WHR), and waist to height ratio (WHtR) were calculated 48.20% (N = 4871), 79.50% (N = 8032), and 83.30% (N = 8314). The Odds Ratio (OR) adjusted of Abnormal body mass index (BMI) for Opium and chronic smoking were 0.54 (CI: 0.47-0.63) and 0.47 (CI:0.40-0.56). OR adjusted Abnormal WC for opium and chronic smoking were calculated 0.65 (CI: 0.53-0.80) and 0.57 (CI:0.46-0.72), respectively. Three variables of opium (OR = 0.54, CI: 0.46-0.64), total opiate drugs (OR = 1.46, CI:1.16-1.83) and chronic smoking (OR = 0.58, CI: 0.48-0.70) remained in the modeling for Abnormal WHR. Which were statistically significant.

CONCLUSION

Significant and inverse relationships were found between obesity and opium, total opiate drugs, and chronic smoking.

Cigarette smoking and nicotine exposure contributes for aberrant insulin signaling and cardiometabolic disorders

Cigarette smoking- and nicotine-mediated dysregulation in insulin-signaling pathways are becoming leading health issues associated with morbidity and mortality worldwide. Many cardiometabolic disorders particularly insulin resistance, polycystic ovary syndrome (PCOS), central obesity and cardiovascular diseases are initiated from exposure of exogenous substances which augment by disturbances in insulin signaling cascade. Among these exogenous substances, nicotine and cigarette smoking are potential triggers for impairment of insulin-signaling pathways. Further, this aberrant insulin signaling is associated with many metabolic complications, which consequently give rise to initiation as well as progression of these metabolic syndromes. Hence, understanding the underlying molecular mechanisms responsible for cigarette smoking- and nicotine-induced altered insulin signaling pathways and subsequent participation in several health hazards are quite essential for prophylaxis and combating these complications. In this article, we have focused on the role of nicotine and cigarette smoking mediated pathological signaling; for instance, nicotine-mediated inhibition of nuclear factor erythroid 2-related factor 2 and oxidative damage, elevated cortisol that may promote central obesity, association PCOS and oxidative stress via diminished nitric oxide which may lead to endothelial dysfunction and vascular inflammation. Pathological underlying molecular mechanisms involved in mediating these metabolic syndromes via alteration of insulin signaling cascade and possible molecular mechanism responsible for these consequences on nicotine exposure have also been discussed.

Effect of Maternal Prepregnancy/Early-Pregnancy Body Mass Index and Pregnancy Smoking and Alcohol on Congenital Heart Diseases: A Parental Negative Control Study

Background Congenital heart diseases (CHDs) are the most common congenital anomaly. The causes of CHDs are largely unknown. Higher prenatal body mass index (BMI), smoking, and alcohol consumption are associated with increased risk of CHDs. Whether these are causal is unclear. Methods and Results Seven European birth cohorts, including 232 390 offspring (2469 CHD cases [1.1%]), were included. We applied negative exposure paternal control analyses to explore the intrauterine effects of maternal BMI, smoking, and alcohol consumption during pregnancy, on offspring CHDs and CHD severity. We used logistic regression, adjusting for confounders and the other parent's exposure and combined estimates using a fixed-effects meta-analysis. In adjusted analyses, maternal overweight (odds ratio [OR], 1.15 [95% CI, 1.01-1.31]) and obesity (OR, 1.12 [95% CI, 0.93-1.36]), compared with normal weight, were associated with higher odds of CHD, but there was no clear evidence of a linear increase in odds across the whole BMI distribution. Associations of paternal overweight, obesity, and mean BMI were similar to the maternal associations. Maternal pregnancy smoking was associated with higher odds of CHD (OR, 1.11 [95% CI, 0.97-1.25]) but paternal smoking was not (OR, 0.96 [95% CI, 0.85-1.07]). The positive association with maternal smoking appeared to be driven by nonsevere CHD cases (OR, 1.22 [95% CI, 1.04-1.44]). Associations with maternal moderate/heavy pregnancy alcohol consumption were imprecisely estimated (OR, 1.16 [95% CI, 0.52-2.58]) and similar to those for paternal consumption. Conclusions We found evidence of an intrauterine effect for maternal smoking on offspring CHDs, but no evidence for higher maternal BMI or alcohol consumption. Our findings provide further support for the importance of smoking cessation during pregnancy.

Lung function impairment and cardiometabolic risks among rural adults: implication for an aging society

BACKGROUND

Early detection and prevention of cardiometabolic risk factors in an increasingly aging society are a global public health concern. Maintaining adequate lung function is important for healthy aging. Few studies exist on lung function impairment and decline in primary healthcare settings, especially among rural adults with cardiometabolic risks. This study aimed to explore the prevalence of impaired lung function and its association with cardiometabolic risks among rural adults.

METHODS

A community-based, cross-sectional study was conducted between March and December 2019 in western coastal Yunlin County, Taiwan. The lung function test was measured by spirometry, based on the American Thoracic Society recommendations. Three lung function parameters were obstructive lung impairment, restrictive lung impairment, and mixed lung impairment. Restrictive, obstructive, and mixed type lung function was categorized as impaired. Cardiometabolic risk factors and metabolic syndrome were based on the national standard and include five abnormal biomarkers, including abdominal obesity, blood pressure, fasting plasma glucose, triglycerides, and decreased high-density cholesterol levels.

RESULTS

The median age of the 1653 (92.9%) participants with complete data was 66 years (interquartile range: 55 to 75 years). The prevalence of impaired lung function was 37%, including 31.7% restrictive, 2.5% obstructive, and 2.7% mixed type. Adults with impaired lung function (86% restrictive type) engaged more in smoking and betel nut chewing, ate fewer vegetables and fruit, and drank less water compared to the normal lung function group. After adjusting for potential confounding variables, multivariate logistic regression analysis showed that cardiometabolic risk factors were independently associated with restrictive lung impairment, while cigarette smoking (OR = 2.27, 95% CI = 1.14-4.53) and betel nut chewing (OR = 2.33, 95% CI = 1.09-5.01) were significantly associated with the obstructive type of lung impairment.

CONCLUSIONS

A high prevalence of restrictive lung impairment, cardiometabolic risks, and unhealthy lifestyles among rural adults were found in this study. For adults with cardiometabolic risks in rural areas, initiating lifestyle modifications with culture-tailored programs to improve lung function should be an important issue for clinicians and primary healthcare providers.

Cigarette Smoking and Estrogen-Related Cancer

Cigarette smoking is a known cause of many cancers, yet epidemiologic studies have found protective associations with the risk of four "estrogen-related" malignancies: endometrial cancer, endometrioid and clear cell ovarian cancers, and thyroid cancer. This review considers epidemiologic and biological aspects of these associations, focusing particularly on estrogen signaling, and contrasts them with those for breast cancer, another estrogen-related malignancy. The observational findings regarding the inverse associations are consistent and remain after adjustment for possible confounding factors. In general, women who smoke do not have lower circulating estrogen levels than nonsmokers, eliminating one possible explanation for reduced risks of these malignancies. For endometrial and endometrioid ovarian cancer, the negative associations could plausibly be explained by interference with signaling through the estrogen receptor α. However, this is unlikely to explain the lower risks of thyroid and clear cell ovarian cancers. For thyroid cancer, an anti-inflammatory effect of nicotine and reduced TSH levels from smoking have been proposed explanations for the inverse association, but both lack convincing evidence. While the overall impact of cigarette smoking is overwhelmingly negative, protective associations such as those discussed here can provide potential clues to disease etiology, treatment, and prevention.

Cigarette smoking blocks the benefit from reduced weight gain for insulin action by shifting lipids deposition to muscle

Cigarette smoking (CS) is known to reduce body weight and this often masks its real effect on insulin action. The present study tested the hypothesis that CS can divert lipid deposition to muscles to offset the supposed benefit of reduced body weight gain on insulin signalling in this major site for glucose tolerance (or insulin action). The study was conducted in mice exposed to chronic CS followed by either a chow (CH) diet or a high-fat (HF) diet. CS increased triglyceride (TG) levels in both plasma and muscle despite a reduced body weight gain and adiposity. CS led to glucose intolerance in CH-fed mice and they retained the glucose intolerance that was induced by the HF diet. In adipose tissue, CS increased macrophage infiltration and the mRNA expression of TNFα but suppressed the protein expression of adipose triglyceride lipase and PPARγ. While CS increased hormone-sensitive lipase and suppressed the mRNA expression of leptin, these effects were blunted in HF-fed mice. These results imply that CS impairs insulin signalling in skeletal muscle via accumulated intramuscular lipids from lipolysis and lipodystrophy of adipose tissues. This may explain why smokers may not benefit from insulin sensitising effects of reduced body weight gain.

Association of smoking status and smoking intensity with general and abdominal obesity in a sample of middle-aged men

Aim. To assess the association of smoking status and smoking intensity with general and abdominal obesity in a sample of middle-a ged men.

Material and methods. This study was conducted as a part of the 32-year prospective cohort observation of males from childhood (11-12 years of age). The study included 301 (30,0%) representatives of the initial population sample aged 41-44 years. Age, anthropometric parameters, relationship of smoking status and smoking intensity with general (overweight/obesity) and abdominal obesity were analyzed.

Results. Overweight/obesity were more common in former smokers (78,1%) compared with non-smokers (58,7%; p<0,01). Abdominal obesity, estimated by the waist circumference (WC), was detected more often among former (57,5%) and current smokers (50,7%), and abdominal obesity, estimated by the waist-to-hip ratio, was more common among current smokers, compared with non-smokers (37,0%; p<0,01, p<0,05 and p<0,05 respectively). A direct linear relationship was found between the intensity of current smoking and indicators of abdominal obesity in terms of waist-to-hip ratio (P for trend=0,004) and a direct linear relationship between intensity of former smoking and general obesity estimated by BMI (P for trend = 0,001), and abdominal obesity estimated by waist-tohip ratio (P for trend=0,004). The probability of developing abdominal obesity in current smokers with WC≥94,0 cm and with waist-to-hip ratio ≥0,9 was 1,8 and 2 times higher, respectively, than in non-smokers, but lower compared to former smokers. The risk of overweight/obesity and abdominal obesity in former smokers was 2,5 and 2,3 times higher, respectively, than in non-smokers. The 10-year risk of fatal CVD in nonsmokers and former smokers was lower than in current smokers (0,8% and 0,9% vs 1,8%; p<0,001 and p<0,001, respectively).

Conclusion. High intensity of smoking among current smokers is associated with a higher probability of developing abdominal obesity, and in former smokers — with a higher probability of developing general and abdominal obesity. Former smokers, compared to current smokers, are at a lower risk of developing fatal cardiovascular diseases. Smoking cessation activities should be aimed at minimizing weight gain after quitting smoking and developing tobacco control programs.

Association of smoking with abdominal adipose deposition and muscle composition in Coronary Artery Risk Development in Young Adults (CARDIA) participants at mid-life: A population-based cohort study

BACKGROUND

Smokers have lower risk of obesity, which some consider a "beneficial" side effect of smoking. However, some studies suggest that smoking is simultaneously associated with higher central adiposity and, more specifically, ectopic adipose deposition. Little is known about the association of smoking with intermuscular adipose tissue (IMAT), an ectopic adipose depot associated with cardiovascular disease (CVD) risk and a key determinant of muscle quality and function. We tested the hypothesis that smokers have higher abdominal IMAT and lower lean muscle quality than never smokers.

METHODS AND FINDINGS

We measured abdominal muscle total, lean, and adipose volumes (in cubic centimeters) and attenuation (in Hounsfield units [HU]) along with subcutaneous (SAT) and visceral adipose tissue (VAT) volumes using computed tomography (CT) in 3,020 middle-aged Coronary Artery Risk Development in Young Adults (CARDIA) participants (age 42-58, 56.3% women, 52.6% white race) at the year 25 (Y25) visit. The longitudinal CARDIA study was initiated in 1985 with the recruitment of young adult participants (aged 18-30 years) equally balanced by female and male sex and black and white race at 4 field centers located in Birmingham, AL, Chicago, IL, Minneapolis, MN, and Oakland, CA. Multivariable linear models included potential confounders such as physical activity and dietary habits along with traditional CVD risk factors. Current smokers had lower BMI than never smokers. Nevertheless, in the fully adjusted multivariable model with potential confounders, including BMI and CVD risk factors, adjusted mean (95% CI) IMAT volume was 2.66 (2.55-2.76) cm3 in current smokers (n = 524), 2.36 (2.29-2.43) cm3 in former smokers (n = 944), and 2.23 (2.18-2.29) cm3 in never smokers (n = 1,552) (p = 0.007 for comparison of former versus never smoker, and p < 0.001 for comparison of current smoker versus never and former smoker). Moreover, compared to participants who never smoked throughout life (41.6 [41.3-41.9] HU), current smokers (40.4 [39.9-40.9] HU) and former smokers (40.8 [40.5-41.2] HU) had lower lean muscle attenuation suggesting lower muscle quality in the fully adjusted model (p < 0.001 for comparison of never smokers with either of the other two strata). Among participants who had ever smoked, pack-years of smoking exposure were directly associated with IMAT volume (β [95% CI]: 0.017 [0.010-0.025]) (p < 0.001). Despite having less SAT, current smokers also had higher VAT/SAT ratio than never smokers. These findings must be viewed with caution as residual confounding and/or reverse causation may contribute to these associations.

CONCLUSIONS

We found that, compared to those who never smoked, current and former smokers had abdominal muscle composition that was higher in adipose tissue volume, a finding consistent with higher CVD risk and age-related physical deconditioning. These findings challenge the belief that smoking-associated weight loss or maintenance confers a health benefit.

Associations of maternal quitting, reducing, and continuing smoking during pregnancy with longitudinal fetal growth: Findings from Mendelian randomization and parental negative control studies

BACKGROUND

Maternal smoking during pregnancy is an established risk factor for low infant birth weight, but evidence on critical exposure windows and timing of fetal growth restriction is limited. Here we investigate the associations of maternal quitting, reducing, and continuing smoking during pregnancy with longitudinal fetal growth by triangulating evidence from 3 analytical approaches to strengthen causal inference.

METHODS AND FINDINGS

We analysed data from 8,621 European liveborn singletons in 2 population-based pregnancy cohorts (the Generation R Study, the Netherlands 2002-2006 [n = 4,682]) and the Born in Bradford study, United Kingdom 2007-2010 [n = 3,939]) with fetal ultrasound and birth anthropometric measures, parental smoking during pregnancy, and maternal genetic data. Associations with trajectories of estimated fetal weight (EFW) and individual fetal parameters (head circumference, femur length [FL], and abdominal circumference [AC]) from 12-16 to 40 weeks' gestation were analysed using multilevel fractional polynomial models. We compared results from (1) confounder-adjusted multivariable analyses, (2) a Mendelian randomization (MR) analysis using maternal rs1051730 genotype as an instrument for smoking quantity and ease of quitting, and (3) a negative control analysis comparing maternal and mother's partner's smoking associations. In multivariable analyses, women who continued smoking during pregnancy had a smaller fetal size than non-smokers from early gestation (16-20 weeks) through to birth (p-value for each parameter < 0.001). Fetal size reductions in continuing smokers followed a dose-dependent pattern (compared to non-smokers, difference in mean EFW [95% CI] at 40 weeks' gestation was -144 g [-182 to -106], -215 g [-248 to -182], and -290 g [-334 to -247] for light, moderate, and heavy smoking, respectively). Overall, fetal size reductions were most pronounced for FL. The fetal growth trajectory in women who quit smoking in early pregnancy was similar to that of non-smokers, except for a shorter FL and greater AC around 36-40 weeks' gestation. In MR analyses, each genetically determined 1-cigarette-per-day increase was associated with a smaller EFW from 20 weeks' gestation to birth in smokers (p = 0.01, difference in mean EFW at 40 weeks = -45 g [95% CI -81 to -10]) and a greater EFW from 32 weeks' gestation onwards in non-smokers (p = 0.03, difference in mean EFW at 40 weeks = 26 g [95% CI 5 to 47]). There was no evidence that partner smoking was associated with fetal growth. Study limitations include measurement error due to maternal self-report of smoking and the modest sample size for MR analyses resulting in unconfounded estimates being less precise. The apparent positive association of the genetic instrument with fetal growth in non-smokers suggests that genetic pleiotropy may have masked a stronger association in smokers.

CONCLUSIONS

A consistent linear dose-dependent association of maternal smoking with fetal growth was observed from the early second trimester onwards, while no major growth deficit was found in women who quit smoking early in pregnancy except for a shorter FL during late gestation. These findings reinforce the importance of smoking cessation advice in preconception and antenatal care and show that smoking reduction can lower the risk of impaired fetal growth in women who struggle to quit.

Associations of tobacco smoking with body mass distribution; a population-based study of 65,875 men and women in midlife

BACKGROUND

Studies indicate an effect of smoking toward abdominal obesity, but few assess hip and waist circumferences (HC and WC) independently. The present study aimed to assess the associations of smoking status and volume smoked with HC and WC and their ratio in a population with low prevalence of obesity together with high prevalence of smoking.

METHODS

We used cross-sectional survey data from 11 of a total 19 Norwegian counties examined in 1997-99 including 65,875 men and women aged 39-44 years. Analysis of associations were adjusted for confounding by socioeconomic position, health indicators, and additionally for BMI.

RESULTS

Compared with never-smokers, when adjusting for confounders and in addition for BMI, mean HC remained lower while mean WC and waist-hip-ratio (WHR) were higher in current smokers. The finding of a lower HC and higher WHR level among smokers was consistent by sex and in strata by levels of education and physical activity, while the finding of higher WC by smoking was less consistent. Among current smokers, BMI-adjusted mean HC decreased whereas WC and WHR increased by volume smoked. Compared with current smokers, former smokers had higher BMI-adjusted HC, lower WHR and among women WC was lower.

CONCLUSIONS

The main finding in this study was the consistent negative associations of smoking with HC. In line with the hypothesis that lower percentage gluteofemoral fat is linked with higher cardiovascular risk, our results suggest that smoking impacts cardiovascular risk through mechanisms that reduce the capacity of fat storage in the lower body region.

Causal relationships between obesity and the leading causes of death in women and men

Obesity traits are causally implicated with risk of cardiometabolic diseases. It remains unclear whether there are similar causal effects of obesity traits on other non-communicable diseases. Also, it is largely unexplored whether there are any sex-specific differences in the causal effects of obesity traits on cardiometabolic diseases and other leading causes of death. We constructed sex-specific genetic risk scores (GRS) for three obesity traits; body mass index (BMI), waist-hip ratio (WHR), and WHR adjusted for BMI, including 565, 324, and 337 genetic variants, respectively. These GRSs were then used as instrumental variables to assess associations between the obesity traits and leading causes of mortality in the UK Biobank using Mendelian randomization. We also investigated associations with potential mediators, including smoking, glycemic and blood pressure traits. Sex-differences were subsequently assessed by Cochran's Q-test (Phet). A Mendelian randomization analysis of 228,466 women and 195,041 men showed that obesity causes coronary artery disease, stroke (particularly ischemic), chronic obstructive pulmonary disease, lung cancer, type 2 and 1 diabetes mellitus, non-alcoholic fatty liver disease, chronic liver disease, and acute and chronic renal failure. Higher BMI led to higher risk of type 2 diabetes in women than in men (Phet = 1.4×10-5). Waist-hip-ratio led to a higher risk of chronic obstructive pulmonary disease (Phet = 3.7×10-6) and higher risk of chronic renal failure (Phet = 1.0×10-4) in men than women. Obesity traits have an etiological role in the majority of the leading global causes of death. Sex differences exist in the effects of obesity traits on risk of type 2 diabetes, chronic obstructive pulmonary disease, and renal failure, which may have downstream implications for public health.

MR-pheWAS with stratification and interaction: Searching for the causal effects of smoking heaviness identified an effect on facial aging

Mendelian randomization (MR) is an established approach to evaluate the effect of an exposure on an outcome. The gene-by-environment (GxE) study design can be used to determine whether the genetic instrument affects the outcome through pathways other than via the exposure of interest (horizontal pleiotropy). MR phenome-wide association studies (MR-pheWAS) search for the effects of an exposure, and can be conducted in UK Biobank using the PHESANT package. In this proof-of-principle study, we introduce the novel GxE MR-pheWAS approach, that combines MR-pheWAS with the use of GxE interactions. This method aims to identify the presence of effects of an exposure while simultaneously investigating horizontal pleiotropy. We systematically test for the presence of causal effects of smoking heaviness-stratifying on smoking status (ever versus never)-as an exemplar. If a genetic variant is associated with smoking heaviness (but not smoking initiation), and this variant affects an outcome (at least partially) via tobacco intake, we would expect the effect of the variant on the outcome to differ in ever versus never smokers. We used PHESANT to test for the presence of effects of smoking heaviness, instrumented by genetic variant rs16969968, among never and ever smokers respectively, in UK Biobank. We ranked results by the strength of interaction between ever and never smokers. We replicated previously established effects of smoking heaviness, including detrimental effects on lung function. Novel results included a detrimental effect of heavier smoking on facial aging. We have demonstrated how GxE MR-pheWAS can be used to identify potential effects of an exposure, while simultaneously assessing whether results may be biased by horizontal pleiotropy.

The Prevalence of Smoking in 41-43-Year-Old Males and its Relation to Some Risk Factors

Aim. To evaluate the prevalence of smoking in 41-43-year-old men living in Moscow and its association with other chronic non-communicable diseases risk factors.Material and methods. People of male sex were prospectively followed up during 32 years since childhood (11-12 years). Only 301 (30%) representatives of 1005 initially enrolled people were examined after 32 years. The examination included: survey by a standard questionnaire (the passport data, the level of physical activity, bad habits – smoking, alcohol consumption); three-time blood pressure measurement; assessment of heart rate; measurement of weight and height, thickness of skin folds (over the triceps, under the scapula and on the abdomen); waist circumference.Results. Almost 50% of 41-44-year-old males smoked every day; less than a third of the study participants had never smoked. Every fifth of the smokers smoked less than 10 cigarettes per day while more than a half of them – a pack and more. The vast majority of the past smokers (85.2%) had stopped smoking at their own will and only very few (1.2%) by doctor’s advice. The intensity of smoking according to the pack/year index was >10 in almost 81.9% of the current smokers. The past smokers had abdominal obesity significantly more often than the non-smokers and the current smokers (57.5% vs 37% and 50.7%, respectively). The current smokers revealed the significantly higher risk of hypertension. The past smokers had 2.5 times higher risk of general obesity and 2.3 times higher one – of abdominal obesity as compared to the non-smokers. The intensity of smoking at the present time correlated with heart rate (HR). The past smokers (who smoked ≥20 cigarettes/day) as compared to the non-smokers had significantly higher HR, the Quetelet index, thickness of skin fold over the triceps and on the abdomen. The currents smokers revealed correlation of the status of smoking with HR, while the past smokers – with such parameters as the Quetelet index, waist circumference, thickness of skin fold under the scapula and over the triceps and no correlation with HR. The current smokers had significantly higher the 10-year risk of death as compared to thepast smokers and the non-smokers. Conclusion. Smoking is one of the most important risk factors of development of chronic non-communicable diseases. The struggle against smoking must be promoted, while close attention should be paid to people who had stopped smoking as a group of risk of cardiovascular disease onset. 

Is smoking heaviness causally associated with alcohol use? A Mendelian randomization study in four European cohorts

Background

Observational studies have shown that tobacco and alcohol use co-occur, but it is not clear whether this relationship is causal.

Methods

Using data from the Avon Longitudinal Study of Parents and Children (ALSPAC) and UK Biobank, we used observational methods to test the hypothesis that smoking heaviness increases alcohol consumption. Mendelian randomization (MR) analyses were then used to test the causal relationship between smoking heaviness and alcohol consumption using 55 967 smokers from four European studies [ALSPAC, The Nord-Trøndelag Health Study (HUNT), the Copenhagen General Population Study (CGPS) and UK Biobank]. MR analyses used rs1051730/rs16969968 as a genetic proxy for smoking heaviness.

Results

Observational results provided evidence of an association between cigarettes per day and weekly alcohol consumption (increase in units of alcohol per additional cigarette smoked per day = 0.10, 95% confidence interval (CI) 0.05 to 0.15, P ≤ 0.001 in ALSPAC; and 0.48, 95% CI 0.45 to 0.52, P ≤ 0.001 in UK Biobank). However, there was little evidence for an association between rs1051730/rs16969968 and units of alcohol consumed per week across ALSPAC, HUNT, CGPS and UK Biobank (standard deviation increase in units of alcohol per additional copy of the risk allele = –0.004, 95% CI –0.023 to 0.016, P=0.708, I² = 51.9%). We had 99% and 88% power to detect a change of 0.03 and 0.02 standard deviation units of alcohol per additional copy of the risk allele, respectively.

Conclusions

Previously reported associations between smoking and alcohol are unlikely to be causal, and may be the result of confounding and/or reverse causation. This has implications for public health research and intervention research.

Smoking and Increased White and Red Blood Cells

Objective—

Whether tobacco smoking causally affects white and red blood cells and thrombocyte counts is unknown. Using a Mendelian randomization approach, we tested the hypothesis that smoking causes increases in these blood cell indices.

Approach and Results—

We included 104 607 white Danes aged 20 to 100 years from the Copenhagen General Population Study with information on blood cell indices, smoking habits, and CHRNA3 (alpha 3 nicotinic cholinergic receptor) rs1051730 genotype, where the T allele causes higher tobacco consumption; 41 759 were former smokers and 17 852 current smokers. In multivariable adjusted observational analyses and compared with never smokers, white blood cells were associated with up to 19% increases, thrombocytes with up to 4.7% increases, and red blood cell indices with up to 2.3% increases in former and current smokers. All associations were dose dependent, with tobacco consumption but for white blood cells and thrombocytes also dependent on smoking cessation time in former smokers; highest increases were for <1-year smoking cessation and lowest increases for >10-year smoking cessation. In age- and sex-adjusted genetic analyses, percent differences per T allele increase in current smokers were 1.15% (95% CI, 0.61%–1.68%) for leukocytes, 1.07% (0.38%–1.76%) for neutrophils, 1.34% (0.66%–2.02%) for lymphocytes, 1.50% (0.83%–2.18%) for monocytes, −0.60% (−1.91% to 0.74%) for eosinophils, 0.17% (−0.94% to 1.29%) for basophils, 0.38% (−0.17% to 0.93%) for thrombocytes, 0.04% (−0.14% to 0.23%) for erythrocytes, 0.34% (0.17% to 0.50%) for hematocrit, 0.26% (0.09% to 0.43%) for hemoglobin, and 0.29% (0.18% to 0.41%) for mean corpuscular volume.

Conclusions—

Smoking causes increased blood leukocytes, neutrophils, lymphocytes, and monocytes, as well as increased hematocrit, hemoglobin, and mean corpuscular volume. The observational smoking relationships were long term for white blood cells and short term for red blood cell indices.

The effect of body mass index on smoking behaviour and nicotine metabolism: a Mendelian randomization study

Given clear evidence that smoking lowers weight, it is possible that individuals with higher body mass index (BMI) smoke in order to lose or maintain their weight. We performed Mendelian randomization (MR) analyses of the effects of BMI on smoking behaviour in UK Biobank and the Tobacco and Genetics Consortium genome-wide association study (GWAS), on cotinine levels and nicotine metabolite ratio (NMR) in published GWAS and on DNA methylation in the Avon Longitudinal Study of Parents and Children. Our results indicate that higher BMI causally influences lifetime smoking, smoking initiation, smoking heaviness and also DNA methylation at the aryl-hydrocarbon receptor repressor (AHRR) locus, but we do not see evidence for an effect on smoking cessation. While there is no strong evidence that BMI causally influences cotinine levels, suggestive evidence for a negative causal influence on NMR may explain this. There is a causal effect of BMI on smoking, but the relationship is likely to be complex due to opposing effects on behaviour and metabolism.

The associations between smoking and obesity in northeast China: a quantile regression analysis

Obesity is a risk factors of chronic diseases, and smoking is associated with both chronic diseases and obesity. There were some controversies about the associations between smoking and obesity. Thus, our study aimed to explore the associations of smoking with obesity, using body mass index (BMI) and waist circumference (WC) as obesity indices in northeast China. We enrolled a sample of 16,412 participants in Jilin province aged 18-79 in this study, which were derived from a cross-sectional survey in 2012. We used quantile regression (QR) models to identify the associations of smoking with obesity in different quantiles of BMI (or WC) by genders. The differences of BMI and WC by genders were statistically significant (p < 0.05). In conclusion, compared with current non-smokers, current smokers had lower BMI but higher WC. As increasing of WC, the association of WC with smoking was getting stronger, especially in females.

The association between smoking and cardiometabolic risk among male adults with disabilities in Taiwan

BACKGROUND

Individuals with disabilities have health needs similar to the general population. Smoking and metabolic syndrome have emerged as major cardiovascular risks that contribute to systemic inflammation and mortality. However, few studies have focused on the association between smoking and cardiometabolic risks in adult men with disabilities.

AIMS

This study explored the prevalence of smoking and its association with cardiometabolic risk and associated factors among male adults with disabilities.

METHODS

This study was part of a nurse-led health-promotion program designed to examine the health needs in health programs for adults with disabilities. A community-based, cross-sectional study was conducted between July 2013-December 2014, in Chiayi County, Taiwan.

RESULTS

Of the total of 964 male participants enrolled in this study, 874 (90.7%) participants had complete data sets. The prevalence of cigarette smoking and metabolic syndrome were 42%, and 33.3%, respectively. More than half (62.7%) had high blood pressure and 43.5% had central obesity. Compared with non-smokers, smokers tended to engage in less frequent regular exercise ( p<0.001), eat fewer vegetables and fruit ( p<0.05), and drink less water ( p<0.05). After adjusting for potential confounding variables, multivariable logistic regression analysis showed that smoking was an independent factor for cardiometabolic risk.

CONCLUSION

The present findings show a high prevalence of cigarette smoking, unhealthy lifestyle, and cardiometabolic risk among adult men with disabilities. Clinicians and primary healthcare providers should reduce the consequences thereof by initiating innovative health promotion programs.

Are Risk Factors for Coronary Artery Disease Different in Persons With and Without Obesity?

BACKGROUND

Although obesity is an independent risk factor for coronary artery disease (CAD), observational studies have found that persons with obesity have a better prognosis in established CAD compared with those with a normal body weight, suggesting that the underlying risk factors might differ between the two groups. In this study, we studied risk factors for CAD in persons with and without obesity in a Middle Eastern setting where obesity is endemic.

METHODS

Five hundred and fifty-six patients referred for elective coronary catheterization at Prince Hamza Hospital, Amman were included in a cross-sectional study. Patients with CAD (n = 353; 63.5%) were compared to patients with a normal coronary angiography (n = 203; 36.5%). Associations between CAD and baseline variables were assessed in multivariate logistic regression models.

RESULTS

In persons with obesity, male sex [adjusted odds ratio (AOR) = 2.62, 95% confidence interval (CI): 1.37-4.99], increasing age (45-54 years: AOR = 5.00, 95% CI: 2.01-12.48; 55-64 years: AOR = 3.77, 95% CI: 1.39-10.23; ≥65 years: AOR = 13.87, 95% CI: 4.62-41.63), diabetes mellitus (AOR = 2.79, 95% CI: 1.49-5.22), and smoking (AOR = 2.25, 95% CI: 1.12-4.50) were strong and significant predictors of CAD. The same risk factors were identified in persons without obesity, but in addition, waist circumference (per 1 cm increment: AOR = 1.04, 95% CI: 1.01-1.07) was a significant predictor of CAD in this group.

CONCLUSIONS

Sex, age, diabetes mellitus, and smoking predicted CAD in all patients. Waist circumference only predicted CAD in persons without obesity, suggesting that normal-weight central obesity might be an important risk factor in this setting.

Association of current and former smoking with body mass index: A study of smoking discordant twin pairs from 21 twin cohorts

Background

Smokers tend to weigh less than never smokers, while successful quitting leads to an increase in body weight. Because smokers and non-smokers may differ in genetic and environmental family background, we analysed data from twin pairs in which the co-twins differed by their smoking behaviour to evaluate if the association between smoking and body mass index (BMI) remains after controlling for family background.

Methods and findings

The international CODATwins database includes information on smoking and BMI measured between 1960 and 2012 from 156,593 twin individuals 18–69 years of age. Individual-based data (230,378 measurements) and data of smoking discordant twin pairs (altogether 30,014 pairwise measurements, 36% from monozygotic [MZ] pairs) were analysed with linear fixed-effects regression models by 10-year periods. In MZ pairs, the smoking co-twin had, on average, 0.57 kg/m² lower BMI in men (95% confidence interval (CI): 0.49, 0.70) and 0.65 kg/m² lower BMI in women (95% CI: 0.52, 0.79) than the never smoking co-twin. Former smokers had 0.70 kg/m² higher BMI among men (95% CI: 0.63, 0.78) and 0.62 kg/m² higher BMI among women (95% CI: 0.51, 0.73) than their currently smoking MZ co-twins. Little difference in BMI was observed when comparing former smoking co-twins with their never smoking MZ co-twins (0.13 kg/m², 95% CI 0.04, 0.23 among men; -0.04 kg/m², 95% CI -0.16, 0.09 among women). The associations were similar within dizygotic pairs and when analysing twins as individuals. The observed series of cross-sectional associations were independent of sex, age, and measurement decade.

Conclusions

Smoking is associated with lower BMI and smoking cessation with higher BMI. However, the net effect of smoking and subsequent cessation on weight development appears to be minimal, i.e. never more than an average of 0.7 kg/m².

Assessing the relationship between smoking and abdominal obesity in a National Survey of Adolescents in Brazil

Abdominal obesity is even a stronger risk factor than overall obesity for noncommunicable chronic diseases. We examined the association between smoking and abdominal obesity among adolescents. Analyses were based on 38,813 subjects aged 15-17 years from the Study of Cardiovascular Risks in Adolescents (ERICA), a Brazilian school-based national survey. Abdominal obesity was defined considering waist circumference (WC) percentiles. Statistical analyses, stratified by sex, considered the sample complex design. Poisson regression with robust variance was used to estimate smoker-to-nonsmoker abdominal obesity prevalence ratio (PR), adjusting by sociodemographic and lifestyle variables. Higher prevalence of abdominal obesity was observed among adolescents who consumed >1 cigarettes/day, comparing to nonsmokers: considering WC >80th percentile, adjusted-PR for boys was 1.27 [95%CI:1.05,1.52] and, for girls, 1.09 [95%CI:1.00,1.19]; using the 90th percentile, adjusted-PR were 2.24 [95%CI:1.70,2.94] and 1.27 [95%CI:1.12,1.46], respectively for male and female adolescents. Our findings suggest a positive association between cigarette consumption and the prevalence of abdominal obesity, for both boys and girls. Although other studies had found this association in adults, our study contributes to this discussion by assessing it in adolescents using a nationwide representative sample of medium and large municipalities.

Role of obesity in smoking behaviour: Mendelian randomisation study in UK Biobank

OBJECTIVE

To determine whether body mass index, body fat percentage, and waist circumference influence smoking status and intensity.

DESIGN

Mendelian randomisation study.

SETTING

UK Biobank, with replication of results from the Tobacco and Genetics (TAG) consortium.

PARTICIPANTS

European descent participants from the UK Biobank cohort (n=372 791) and the TAG consortium (n=74 035).

MAIN OUTCOME MEASURES

Risk of current and past smoking, number of cigarettes smoked per day, age of smoking initiation.

RESULTS

The Mendelian randomisation analysis indicated that each standard deviation increment in body mass index (4.6) increased the risk of being a smoker (odds ratio 1.18 (95% confidence interval 1.13 to 1.23), P<0.001). This association was replicated in the TAG consortium data (1.19 (1.06 to 1.33), P=0.003). Furthermore, each standard deviation increment in body mass index was estimated to increase smoking intensity by 0.88 cigarettes per day (95% confidence interval 0.50 to 1.26, P<0.001) in UK Biobank and 1.27 cigarettes per day in the TAG consortium (0.46 to 2.07, P=0.002). Similar results were also seen for body fat percentage and waist circumference in both UK Biobank and the TAG consortium data.

CONCLUSIONS

These results strongly suggest that higher adiposity influences smoking behaviour and could have implications for the implementation of public health interventions aiming to reduce the prevalence of these important risk factors.

Tobacco smoking and the risk of diverticular disease - a systematic review and meta-analysis of prospective studies

AIM

This systematic review and meta-analysis aimed to clarify whether tobacco smoking is associated with an increased risk of diverticular disease.

METHOD

The PubMed and Embase databases were searched for studies of smoking and diverticular disease up to 19 February 2016. Prospective studies that reported adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of diverticular disease associated with current or previous smoking were included. Summary RRs were estimated using a random effects model.

RESULTS

We identified five prospective studies which comprised 6076 cases of incident diverticular disease (diverticulosis and diverticulitis) among 385 291 participants and three studies with 1118 cases of complications related to diverticular disease (abscess or perforation) among 292 965. The summary RR for incident diverticular disease was 1.36 (95% CI 1.15-1.61, I²  = 84%, n = 4) for current smokers, 1.17 (95% CI 1.05-1.31, I²  = 49%, n = 4) for former smokers and 1.29 (95% CI 1.16-1.44, I²  = 62%, n = 5) for ever smokers. The summary RR was 1.11 (95% CI 0.99-1.25, I²  = 82%, n = 4) per 10 cigarettes per day. Although there was some indication of nonlinearity there was a dose-dependent positive association with increasing number of cigarettes smoked per day. There was some evidence that smoking also increases the risk of complications of diverticular disease, but the number of studies was small.

CONCLUSION

The current meta-analysis provides evidence that tobacco smoking is associated with an increased incidence of diverticular disease and related complications.

The causal role of smoking on the risk of hip or knee replacement due to primary osteoarthritis: a Mendelian randomisation analysis of the HUNT study

OBJECTIVE

Smoking has been associated with a reduced risk of hip and knee osteoarthritis (OA) and subsequent joint replacement. The aim of the present study was to assess whether the observed association is likely to be causal.

METHOD

55,745 participants of a population-based cohort were genotyped for the rs1051730 C > T single-nucleotide polymorphism (SNP), a proxy for smoking quantity among smokers. A Mendelian randomization analysis was performed using rs1051730 as an instrument to evaluate the causal role of smoking on the risk of hip or knee replacement (combined as total joint replacement (TJR)). Association between rs1051730 T alleles and TJR was estimated by hazard ratios (HRs) and 95% confidence intervals (CIs). All analyses were adjusted for age and sex.

RESULTS

Smoking quantity (no. of cigarettes) was inversely associated with TJR (HR 0.97, 95% CI 0.97-0.98). In the Mendelian randomization analysis, rs1051730 T alleles were associated with reduced risk of TJR among current smokers (HR 0.84, 95% CI 0.76-0.98, per T allele), however we found no evidence of association among former (HR 0.97, 95% CI 0.88-1.07) and never smokers (HR 0.97, 95% CI 0.89-1.06). Neither adjusting for body mass index (BMI), cardiovascular disease (CVD) nor accounting for the competing risk of mortality substantially changed the results.

CONCLUSION

This study suggests that smoking may be causally associated with the reduced risk of TJR. Our findings add support to the inverse association found in previous observational studies. More research is needed to further elucidate the underlying mechanisms of this causal association.

Investigating the causal effect of smoking on hay fever and asthma: a Mendelian randomization meta-analysis in the CARTA consortium

Observational studies on smoking and risk of hay fever and asthma have shown inconsistent results. However, observational studies may be biased by confounding and reverse causation. Mendelian randomization uses genetic variants as markers of exposures to examine causal effects. We examined the causal effect of smoking on hay fever and asthma by using the smoking-associated single nucleotide polymorphism (SNP) rs16969968/rs1051730. We included 231,020 participants from 22 population-based studies. Observational analyses showed that current vs never smokers had lower risk of hay fever (odds ratio (OR) = 0·68, 95% confidence interval (CI): 0·61, 0·76; P < 0·001) and allergic sensitization (OR = 0·74, 95% CI: 0·64, 0·86; P < 0·001), but similar asthma risk (OR = 1·00, 95% CI: 0·91, 1·09; P = 0·967). Mendelian randomization analyses in current smokers showed a slightly lower risk of hay fever (OR = 0·958, 95% CI: 0·920, 0·998; P = 0·041), a lower risk of allergic sensitization (OR = 0·92, 95% CI: 0·84, 1·02; P = 0·117), but higher risk of asthma (OR = 1·06, 95% CI: 1·01, 1·11; P = 0·020) per smoking-increasing allele. Our results suggest that smoking may be causally related to a higher risk of asthma and a slightly lower risk of hay fever. However, the adverse events associated with smoking limit its clinical significance.

Genome-wide meta-analysis of 241,258 adults accounting for smoking behaviour identifies novel loci for obesity traits

Few genome-wide association studies (GWAS) account for environmental exposures, like smoking, potentially impacting the overall trait variance when investigating the genetic contribution to obesity-related traits. Here, we use GWAS data from 51,080 current smokers and 190,178 nonsmokers (87% European descent) to identify loci influencing BMI and central adiposity, measured as waist circumference and waist-to-hip ratio both adjusted for BMI. We identify 23 novel genetic loci, and 9 loci with convincing evidence of gene-smoking interaction (GxSMK) on obesity-related traits. We show consistent direction of effect for all identified loci and significance for 18 novel and for 5 interaction loci in an independent study sample. These loci highlight novel biological functions, including response to oxidative stress, addictive behaviour, and regulatory functions emphasizing the importance of accounting for environment in genetic analyses. Our results suggest that tobacco smoking may alter the genetic susceptibility to overall adiposity and body fat distribution.

Causal inference in obesity research

Obesity is a risk factor for a plethora of severe morbidities and premature death. Most supporting evidence comes from observational studies that are prone to chance, bias and confounding. Even data on the protective effects of weight loss from randomized controlled trials will be susceptible to confounding and bias if treatment assignment cannot be masked, which is usually the case with lifestyle and surgical interventions. Thus, whilst obesity is widely considered the major modifiable risk factor for many chronic diseases, its causes and consequences are often difficult to determine. Addressing this is important, as the prevention and treatment of any disease requires that interventions focus on causal risk factors. Disease prediction, although not dependent on knowing the causes, is nevertheless enhanced by such knowledge. Here, we provide an overview of some of the barriers to causal inference in obesity research and discuss analytical approaches, such as Mendelian randomization, that can help to overcome these obstacles. In a systematic review of the literature in this field, we found: (i) probable causal relationships between adiposity and bone health/disease, cancers (colorectal, lung and kidney cancers), cardiometabolic traits (blood pressure, fasting insulin, inflammatory markers and lipids), uric acid concentrations, coronary heart disease and venous thrombosis (in the presence of pulmonary embolism), (ii) possible causal relationships between adiposity and gray matter volume, depression and common mental disorders, oesophageal cancer, macroalbuminuria, end-stage renal disease, diabetic kidney disease, nuclear cataract and gall stone disease, and (iii) no evidence for causal relationships between adiposity and Alzheimer's disease, pancreatic cancer, venous thrombosis (in the absence of pulmonary embolism), liver function and periodontitis.

The CHRNA5-A3-B4 Gene Cluster and Smoking: From Discovery to Therapeutics

Genome-wide association studies (GWASs) have identified associations between the CHRNA5-CHRNA3-CHRNB4 gene cluster and smoking heaviness and nicotine dependence. Studies in rodents have described the anatomical localisation and function of the nicotinic acetylcholine receptors (nAChRs) formed by the subunits encoded by this gene cluster. Further investigations that complemented these studies highlighted the variability of individuals' smoking behaviours and their ability to adjust nicotine intake. GWASs of smoking-related health outcomes have also identified this signal in the CHRNA5-CHRNA3-CHRNB4 gene cluster. This insight underpins approaches to strengthen causal inference in observational data. Combining genetic and mechanistic studies of nicotine dependence and smoking heaviness may reveal novel targets for medication development. Validated targets can inform genetic therapeutic interventions for smoking cessation and tobacco-related diseases.

Smoking status and abdominal obesity among normal- and overweight/obese adults: Population-based FINRISK study

Several studies have reported direct associations of smoking with body mass index (BMI) and abdominal obesity. However, the interplay between them is poorly understood. Our first aim was to investigate the interaction between smoking status and BMI on abdominal obesity (waist circumference, WC). Our second aim was to examine how the association of smoking status with WC varies among normal and overweight/obese men and women. We examined 5833 participants from the National FINRISK 2007 Study. The interactions between smoking and BMI on WC were analyzed. Participants were categorized into eight groups according to BMI (normal weight vs. overweight/obese) and smoking status (never smoker, ex-smoker, occasional/light/moderate daily smoker, heavy daily smoker). The associations between each BMI/smoking status -group and WC were analyzed by multiple regressions, the normal-weight never smokers as the reference group. The smoking status by BMI-interaction on WC was significant for women, but not for men. Among the overweight/obese women, ex-smokers (β = 2.73; 1.99, 3.46) and heavy daily smokers (β = 4.90; 3.35, 6.44) had the highest estimates for WC when adjusted for age, BMI, alcohol consumption and physical activity. In comparison to never smoking overweight/obese women, the β-coefficients of ex-smokers and heavy daily smokers were significantly higher. Among men and normal weight women the β -coefficients did not significantly differ by smoking status. An interaction between smoking status and BMI on abdominal obesity was observed in women: overweight/obese heavy daily smokers were particularly vulnerable for abdominal obesity. This risk group should be targeted for cardiovascular disease prevention.

Lifetime cigarette smoking is associated with abdominal obesity in a community-based sample of Japanese men: The Shiga Epidemiological Study of Subclinical Atherosclerosis (SESSA)

Studies from Western countries suggest that smokers tend to display greater abdominal obesity than non-smokers, despite showing lower weight. Whether this holds true in a leaner population requires clarification. Using indices of abdominal obesity including visceral adipose tissue, we examined whether lifetime cigarette smoking is associated with unfavorable fat distribution among Japanese men. From 2006 to 2008, we conducted a cross-sectional investigation of a community-based sample of Japanese men at 40-64 years old, free of cardiovascular diseases and cancer. Areas of abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were calculated using computed tomography. We divided participants into four groups: never-smokers; and tertiles of pack-years of smoking among ever-smokers. Using multivariable linear regression, we calculated adjusted means of obesity indices (VAT, SAT, VAT-SAT ratio [VSR], and waist-hip ratio [WHR]) for each group, and mean differences between consecutive groups. We analyzed 513 men (median age, 58.2 years; current smokers, 40.1%). Two-thirds showed body mass index (BMI) < 25 kg/m(2) (median, 23.5 kg/m(2)). Overall, greater lifetime smoking group was associated with greater WHR and VSR. On average, one higher smoking group was associated with 0.005 higher WHR (95% CI, 0.001-0.008; P = 0.005) and 0.041 greater VSR (95% CI, 0.009-0.073; P = 0.012) after adjustment for potential confounders, including BMI. In this sample of relatively lean Japanese men, greater lifetime smoking was associated with a metabolically more adverse fat distribution. Although smoking is commonly associated with lower BMI, minimizing the amount of lifetime smoking should be advocated.

Heritability of high sugar consumption through drinks and the genetic correlation with substance use

BACKGROUND

High sugar consumption contributes to the rising prevalence of obesity. Sugar can have rewarding effects that are similar to, but less strong than, the effects of addictive substances. People who consume large amounts of sugar also tend to use more addictive substances, but it is unclear whether this is due to shared genetic or environmental risk factors.

OBJECTIVE

We examined whether there are genetic influences on the consumption of sugar-containing drinks and whether genetic factors can explain the association with substance use.

DESIGN

The frequency of consumption of sugar-containing drinks (e.g., cola, soft drinks, and energy drinks) and addictive substances (nicotine, caffeine, alcohol, cannabis, and illicit drugs) was obtained for 8586 twins who were registered at the Netherlands Twin Register (women: 68.7%; mean ± SD age: 33.5 ± 15.3 y). Participants were categorized as high or low sugar consumers (>1 compared with ≤1 SD above daily consumption in grams) and as high or low substance users (≥2 compared with <2 substances). Through bivariate genetic modeling, genetic and environmental influences on sugar consumption, substance use, and their association were estimated.

RESULTS

Genetic factors explained 48% of the variation in high sugar consumption, whereas unique environmental factors explained 52%. For high substance use, these values were 62% and 38%, respectively. There was a moderate phenotypic association between high sugar consumption and high substance use (r = 0.2), which was explained by genetic factors (59%) and unique environmental factors (41%).

CONCLUSIONS

The positive association between high sugar consumption and high substance use was partly due to unique environmental factors (e.g., social situations). Genetic factors were also of influence, suggesting that neuronal circuits underlying the development of addiction and obesity are related. Further research is needed to identify genes that influence sugar consumption and those that overlap with substance use.