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Smoking may worsen an unfavorable cardiovascular profile through various pathways, including exacerbating inflammation, increasing cholesterol and potassium levels, and decreasing bilirubin and creatinine levels. This is the first cross‑sectional study that confirmed the association between the adverse biochemical profile and smoking status in Poland. However, due to lack of a longitudinal assessment, it would be difficult to infer the temporal association between a risk factor and an outcome. The key finding in this study was the presence of a social gradient in tobacco use in the Polish population, which identified unmarried people with a lower socioeconomic status who live in small towns to be more likely to use tobacco and to have an unfavorable biochemical profile. Temporal relations in mechanisms involved in the gradient observed between biochemical markers and smoking status remain unclear. Therefore, we still need measures targeted at the most disadvantaged to prevent health risks caused by smoking.

Introduction

Smoking has been widely believed to be the strongest single adverse health factor.^1-4 Epidemiological studies have shown a fairly constant association between socioeconomic status and smoking, with a higher prevalence of smoking observed among those who are poorer and less educated.^5,6 Although a negative effect of a low socioeconomic status and smoking on mortality risk and health status has been clearly established, associations between smoking and other biological indicators of health status have not been elucidated yet. Some studies indicated associations among smoking, single clinical parameters, and socioeconomic status.^7-9 Lower body mass was also associated with smoking.¹⁰ Furthermore, smoking, loneliness, and mental health problems were demonstrated to be related.¹¹ In the search for a more precise model of adverse effects of nicotine, attempts have been made to characterize in detail how smoking and other health behaviors are related to biochemical and even metabolomic correlates of smoking effects.^12-14 Elucidating the associations between smoking and selected biological determinants of smoking‑related disease may help to understand their pathomechanism and identify possible ways to decrease the risk. Additionally, the role of new cardiovascular risk factors, such as serum bilirubin and creatinine levels, in the prediction of cardiovascular events need to be better understood also in the context of smoking.^15,16 So far, no study has attempted to compare multiple, both biochemical and socioeconomic, cardiovascular risk profiles between smokers and nonsmokers in Central‑Eastern Europe.

The aim of this study was to assess the relationship among smoking, the pattern of biochemical risk factors, and sociodemographic characteristics in a Central‑Eastern European population, based on data collected in a representative sample of the Polish general population in the NATPOL 2011 (Arterial Hypertension and Other Cardiovascular Disease Risk Factors in Poland [Polish: Nadciśnienie tętnicze oraz inne czynniki ryzyka chorób serca i naczyń w Polsce]) study.

Patients and methods

The NATPOL 2011 survey was designed as a cross‑sectional, representative observational study. It was carried out in a representative sample of Polish residents aged 18 to 79 years. The participants were randomly selected in clusters using a stratified, proportional draw performed in 3 stages. Overall, 2413 subjects (1245 women and 1168 men) participated in the survey. The response rate among respondents who were invited and eligible for the study was 66.4%. The survey fieldwork was carried out by 234 well‑trained nurses who lived in or close to the randomly selected geographical clusters. The participants were examined during 2 home visits. The evaluation of an individual included the following components: completion of a questionnaire, blood pressure readings and anthropometric measurements, and blood and urine sample collection. The questionnaire was completed during the first visit. Blood pressure readings were taken 3 times during the first and the second visit using a fully automatic oscillometric device (A&D, UA 767, Tokyo, Japan). Arterial hypertension was diagnosed according to the 2007 European Society of Hypertension / European Society of Cardiology guidelines for the management of arterial hypertension if during both visits systolic blood pressure was higher than or equal to 140 mm Hg or diastolic blood pressure was higher than or equal to 90 mm Hg, or the patient was taking antihypertensive drugs over the previous 2 weeks because of diagnosed hypertension. Overweight was defined as a body mass index (BMI) between 25 and 29.9 kg/m², and obesity, as BMI ≥30 kg/m². Smoking was defined as active regular smoking of at least 1 cigarette per day. Education levels were divided into the following categories: primary (includes vocational), secondary (includes incomplete higher education, ie, without a master’s degree), and higher education. Blood and urine samples were taken during the second visit, after 10 to 12 hours of fasting. However, participants were allowed to drink water while fasting. Frozen samples were transported to a central laboratory for blood and urine analysis.

The study protocol was approved by the institutional ethics committee at Medical University of Gdańsk and all participants provided written informed consent.

Detailed data on the questionnaire, sample selection, and laboratory parameters were provided elsewhere.¹⁷

Results

Overall, the study included 2413 respondents (1245 women and 1168 men). The mean (SD) age was 47 (17) years in women and 45 (16) years in men. The study group included 331 female smokers (26.6%) and 402 male smokers (34.4%). Former smokers accounted for 21.2% of women and 31.6% of men. More than half of the surveyed women (52.2%) and 34% of men declared that they had never smoked tobacco. The percentage of smokers differed significantly between men and women (P <0.001).

The mean or median values of the parameters analyzed in the study in men and women are presented in table 1. Men were found to have significantly higher BMI, apolipoprotein B (apoB), bilirubin, creatinine, potassium, and fasting blood glucose levels as well as systolic and diastolic blood pressure.