|Ahead of print publication
Comparative study of lipid profile among young smokers and nonsmokers in south Indian population
Abhinav Kumar1, Srikanth Narayanaswamy2
1 Department of Gastroenterology, M. S. Ramaiah Hospitals, Bengaluru, Karnataka, India
2 Department of General Medicine, M. S. Ramaiah Hospitals, Bengaluru, Karnataka, India, Bengaluru
|Date of Submission||08-Nov-2021|
|Date of Decision||08-May-2022|
|Date of Acceptance||09-May-2022|
|Date of Web Publication||14-Mar-2023|
Department of General Medicine, M. S. Ramaiah Hospitals, Bengaluru-560 054, Karnataka
Source of Support: None, Conflict of Interest: None
Background: In India, the predominant way of tobacco consumption is by smoking cigarettes, which is a vital risk factor for atherosclerotic vascular disease, which in turn is affected by abnormality in the lipid profile. Aim: To evaluate the alteration in the serum lipid profile between young smokers and nonsmokers. Materials and methods: The study included a total of 148 participants, who were divided into light (n = 25), moderate (n = 25), heavy (n = 24) smokers ("S" group), and nonsmokers ("NS" group, n = 74). Along with demographic data, blood samples were collected after overnight fasting under aseptic conditions. The samples were centrifuged and the lipid profile estimation of substances including serum cholesterol, triglycerides, high-density lipoprotein cholesterol, low- and very low-density lipoprotein cholesterol were performed. Independent sample t test and one-way analysis of variance were employed for statistical analysis, considering P ≤.05 as significant. Results: The mean years of smoking were 7.91 ± 4.67 years and average cigarettes smoked per day were 13.43 ± 6.66. The inter-group difference in the lipid profiles were significant (P <.001). An increasing trend of mean cholesterol, low-density lipoprotein cholesterol, triglycerides, and very low-density lipoprotein cholesterol with regard to lower to higher smoking index, while high-density lipoprotein cholesterol levels significantly showed decreasing trend with regard to lower to higher smoking index (P <.001). Conclusion: The present study reported abnormal lipid level in smokers in comparison to the nonsmokers, with the amount and duration of smoking also influencing dyslipidemia.
Keywords: Cholesterol, dyslipidemias, HDL-C, LDL-C, smoking, VLDL-C
|How to cite this URL:|
Kumar A, Narayanaswamy S. Comparative study of lipid profile among young smokers and nonsmokers in south Indian population. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2023 Mar 24]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=371651
| Introduction|| |
Globally, consuming tobacco is one of the leading causes of preventable morbidity and mortality. Tobacco consumption, a leading cause for noncommunicable disease, accounts for 63% mortality at a global level., The low- and middle-income countries are worst affected with 80% mortality rate due to tobacco consumption. According to a report from the World Health Organization, the projected population of smokers during the year 2020–2030 is estimated to be 1.8 billion, which could increase to 2.2 billion by the year 2050.
In India, the predominant way of tobacco consumption is by smoking cigarettes, which serves as a vital risk factor for stroke, peripheral vascular disease, atherosclerosis, type 2 diabetes, and cancer along with a stronger relationship with periodontal disease and gastric ulcers., The major underlying risk factor for atherosclerotic vascular disease is the abnormalities in the plasma lipoproteins. Earlier conducted studies have indicated a direct relationship between smoking and alterations in the lipid profile.,,,
The low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) are atherogenic factors and the high-density lipoprotein cholesterol (HDL-C) is a protective factor against coronary atherosclerosis. Cigarette smoking causes an increase in the concentrations of plasma catecholamine, which in turn induces lipolysis, releasing free fatty acids that gets deposited in the liver. The Framingham Heart Study was the first epidemiological study that has pointed out the significant association of smoking with cardiovascular diseases, and thus reduction in smoking in turn decreases the ST-segment elevation myocardial infarction events.
The specific mechanism by which smoking disturbs the lipid metabolism is not clearly understood. The lipid metabolism of passive or nonsmokers is also affected. In India, there is paucity of data describing the association between smoking and dyslipidemia. Therefore, this study was aimed at evaluating the alteration in the serum lipid profile if any between young smokers and nonsmokers.
| Materials and Methods|| |
This prospective study was conducted in the Department of Medicine for a period of 2 years (December 2013 to April 2015) at a health care center in Bengaluru. Approval from the institutional ethics committee and the study participants were acquired before commencement of the study.
The study included a total of 148 participants (based on convenience sampling), aged 20 to 40 years, who had attended the outpatient department of the hospital, volunteers from the general public, college students, patient's attendants, and hospital staff with smoking history.
Individuals with a known case of diabetes mellitus, hypertension, chronic kidney disease, chronic liver disease, thyroid dysfunction, and alcohol abuse were excluded from the study. Individuals consuming drugs that could alter lipid profile and cause electrocardiogram abnormalities were also excluded along with obese people with body mass index ≥30 kg/m2.
Smokers ("S") were again divided into 3 groups depending on the number of cigarettes/beedis smoked per day.
- Light smokers (n = 25): 1 to 10 cigarettes or 1 to 15 beedis per day for at least 1 to 5 years.
- Moderate smokers (n = 25): 11 to 20 cigarettes or 16 to 30 beedis per day for at least 6 to 10 years.
- Heavy smokers (n = 24): More than 24 cigarettes or 30 beedis per day for more than 10 years.
Nonsmokers ("NS", n = 74): Age matched healthy individuals who have never smoked or those who left smoking at least 5 years before.
Detailed histories including various demographic factors were noted. Blood samples were collected after overnight fasting under aseptic conditions. The samples were centrifuged and the lipid profile estimation of substances including serum cholesterol (cholesteroloxidase method, coefficient of variation [CV]%: 3.9), triglycerides (TG, enzymatic method, CV%: 3.6), and HDL-C (phosphotungstic method, CV%: 4.7), were measured in fully automated Cobas C analyzer. The LDL-C and VLDL-C were also calculated.[9–12]
The categorical data were expressed as rates, ratios, and proportions, and comparison was done using the χ2 test. The continuous data were expressed as mean ± standard deviation and independent sample t test was used to compare the data. The comparison of more than 2 means was done using one-way analysis of variance. P ≤0.05 was considered as statistically significant.
| Results|| |
All the participants in this study were male. The mean age of participants in the "NS" group was 29.26 ± 5.90 years and that of "S" group was 30.42 ± 6.19 years (P =0.244). The mean body mass index of participants in the "NS" group was 22.19 ± 1.68 kg/m2 and that of "S" group was 22.68 ± 1.73 kg/m2 (P =0.084). The mean systolic blood pressure of participants in the "NS" group was 123.03 ± 6.96 mm Hg (P <.001) and that of "S" group was 127.43 ± 7.29 mm Hg and the respective diastolic blood pressure was 77.32 ± 5.76 mm Hg and 80.08 ± 5.15 mm Hg (P =.003).
According to the Canadian Tobacco Use Monitoring Survey smoking index, 33.78% of all the smokers belonged to the light and heavy smoking category each. The mean years of smoking were 7.91 ± 4.67 years and average cigarettes smoked per day were 13.43 ± 6.66. The distribution of the study population based on the lipid profiles is represented in [Table 1].
The mean lipid profile of the study population is represented in [Table 2]. Mean cholesterol level in the mild smokers was 187.24 ± 23.10 mg/dL, which significantly raised to 219.96 ± 25.29 mg/dL in moderate smokers and further to 239.17 ± 33.81 mg/dL in heavy smokers (P <.001). The mean LDL-C levels in mild smokers was 142.68 ± 21.52 mg/dL, which significantly increased to 166.00 ± 39.80 mg/dL in moderate smokers and 177.75 ± 38.64 mg/dL in heavy smokers (P =0.002). The VLDL-C levels were least in mild smokers (15.82 ± 4.21 mg/dL) compared with moderate (23.91 ± 4.33 mg/dL) and heavy smokers (34.59 ± 7.97 mg/dL; P <.001). The mean HDL-C levels in "S" were also significantly low compared with "NS" (49.25 ± 9.68 vs 56.18 ± 5.12 mg/dL; P <.001).
There was an increasing trend of mean cholesterol, LDL-C, TG, and VLDL-C with regard to lower to higher smoking index, while HDL-C levels significantly showed decreasing trend with regard to lower to higher smoking index (P <.001) [Figure 1].
|Figure 1: Comparing the lipid profile in smokers based on smoking index HDL = high-density lipoprotein, LDL = low-density lipoprotein, TGS = triglycerides, VLDL = very low-density lipoprotein|
Click here to view
| Discussion|| |
Cigarette smoking has been reported to a be modifiable risk factor of atherosclerosis and in turn, a reason for an increase in morbidity and mortality of chronic heart diseases. Cigarette smoking causes dyslipidemia which in turn affects the body functioning. With increase in the number of smokers in India, this study aimed at evaluating the alteration in the serum lipid profile if any between young smokers and nonsmokers.
The average cigarettes smoked per day by our study population was 13.43 ± 6.66. As reported by the National Cancer Institute, an individual smoking between 1 and 10 cigarettes a day has an 87% higher risk of earlier mortality when compared with the nonsmokers. The lipid profiles of majority of the individuals belonging to the "S" group was more toward the abnormal range in comparison to those in the "NS" group.
Results from the INTERHEART study reported a strong and graded relationship between the number of cigarettes smoked by an individual and the risk of myocardial infarction. The study also pointed out that in Southeast Asian countries, the incidence of coronary artery diseases is increasing at an alarming rate among the younger generation and among the different various risk factors, smoking was one of the main causative factors.,
The mean years of smoking from the study participants were 7.91 ± 4.67 years. Studies reported that higher number of pack-years resulted in increased total cholesterol, TG, and LDL-C levels along with a concomitant decrease in HDL-C levels. These observations confirm findings of a direct relationship between increase in the number of years of smoking and abnormal lipid profiles., In our study, the inter-group difference in the lipid profiles were significant (P <.001). The findings were similar to that of previously conducted studies (P <.05)., The pattern of rising mean cholesterol, TG, LDL-C, and VLDL-C levels concomitant with lowering of HDL-C with regard to the smoking index was similar to that of Devarnavadagi et al.
Studies have reported the smoking cessation has resulted in beneficial effects such as reduction in the risk of cardiovascular disease, stroke, myocardial infarction, and total mortality.,, However, reports concerning the relationship between smoking cessation and its impact on the lipid profile is still controversial.,, A recent survey conducted in India reported that the reduction in propensity to smoke was mainly based on residential type and occupation of the respondent. Therefore, by conducting awareness programs and educating smokers about the harmful effects of smoking, we can only hope that the number of smokers further reduces, thereby improving one's health to avoid any future health-related concerns.
The limitations of this study are small sample size, single-centered study, and evaluating only the lipid profile levels among the study population. Future study includes a larger cohort that will evaluate the effect of smoking on cardiovascular health.
In conclusion, the present study reported abnormal lipid level in smokers compared with the nonsmokers, with the amount and duration of smoking also influencing dyslipidemia. This calls for creating awareness among individuals to either stop or limit the number of cigarettes to a minimum to lead a healthy life.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]