Abstract
Objective
We aimed to evaluate the impact of a brief smoking cessation intervention among patients with diabetes.
Methods
This randomized interventional clinical trial involved patients with diabetes who smoked tobacco and attended the outpatient diabetes clinic at Penang Hospital, Malaysia. Participants were randomized into a control group that usual care for patients with diabetes, or an intervention group that received a 5-minute physician-delivered brief counseling session on tobacco cessation using the 5A’s strategy, in addition to usual care. Primary outcome measures were assessed over three visits (every 3–4 months) including mean glycated hemoglobin level, quitting rate, blood pressure, and mean number of cigarettes smoked per day.
Results
In total, 126 participants were finally enrolled in the study, with 63 patients each in the intervention and control groups. There was no significant difference between the two groups with respect to glycemic control, blood pressure, and quitting rate. However, patients in both groups reduced their cigarette consumption.
Conclusions
The present brief smoking cessation intervention did not result in better glycemic control, blood pressure, or quitting rates among patients with diabetes. This patient group may require more intensive guidance for better outcomes.
Introduction
Smoking tobacco is considered an avoidable cause of morbidity and premature mortality worldwide.1,2 In Europe, smokers make up 13.9% of the general population, 12.5% of patients with diabetes, and 14.24% of healthy people. 3 According to the 2019 National Health and Morbidity Survey, Malaysia's smoking prevalence is 21.3% (95% confidence interval: 19.9–22.8). 4 In Iraq, the prevalence of current smoking is 29.4% among those with prediabetes, compared with 25.2% for non-smokers. 5 In recent years, there has been an alarming increase in the prevalence of diabetes mellitus worldwide, as well as in Malaysia.6,7 The association between tobacco smoking and diabetes is becoming increasingly important. Several studies have reported the association between tobacco smoking and poor glycemic control and that smoking increases morbidity and mortality among patients with both type 1 and type 2 diabetes.8–13 Furthermore, smokers have twice the risk of developing diabetes in comparison with non-smokers. 14 A meta-analysis and systematic review identified an association between active tobacco smoking and diabetes mellitus, 15 and the combined prevalence of tobacco use in patients with diabetes was 33% across 14 studies. 16 The World Health Organization (WHO) South-East Asia and Western Pacific regions have higher prevalence rates of tobacco use than those in the Americas, the Middle East and North Africa, Europe, and Central Asia. The global mean prevalence of tobacco use in type 2 diabetes mellitus is 20.81% (95% confidence interval: 18.93–22.76). 17 Quitting tobacco reduces the mortality risk among patients with diabetes within several years after quitting. 18 Therefore, tobacco cessation is strongly recommended to improve glycemic control and to slow the development of diabetic complications.1,19
The International Diabetes Federation guidelines for type 2 diabetes include providing tobacco cessation advice as the standard of care to reduce or stop tobacco consumption.6,20 A systematic study on tobacco reduction in healthy adults found that brief interventions and motivational interviewing are effective ways to stop tobacco use. 21 In England, roughly 50.4% of smokers who visit their physician receive brief smoking guidance. 22 Various studies have used the Screening, Brief Intervention, and Referral for Treatment (SBIRT) model; 23 however, there is good evidence that using nicotine replacement treatment from the quit day onward enhances smoking abstinence, according to Cochrane Tobacco Addiction Group research from 2019 to 2020. 24 Post-cessation weight gain and newly developed obesity and diabetes remain serious concerns, despite the health benefits of stopping smoking.25–27 Intervention is anticipated to improve the clinical outcomes of diabetes care, and ultimately, patient quality of life. Despite the importance of improving glycemic control and screening for microvascular complications, it may be even more important to detect and control major macrovascular risk factors. Although the improvements after quitting smoking may need time to be detected and measured, these improvements should be followed carefully. Studies show that smoking cessation programs can significantly reduce both systolic and diastolic blood pressure (BP), in addition to having an effect on glycemic control.28,29
Previous studies have investigated the effectiveness of tobacco cessation interventions among patients with diabetes who smoke.14,30–39 The main limitation of those studies is that they were not randomized controlled trials (RCTs), and some studies included small samples or had inconclusive results. Consequently, rigorous studies are needed to evaluate the effect of structured tobacco cessation interventions tailored to patients with diabetes on both smoking and diabetes-related outcomes. Previous tobacco cessation intervention studies in other disease conditions such as tuberculosis40–43 and chronic obstructive pulmonary disease have shown the benefits of brief counseling delivered by health care professionals on smoking and disease-related outcomes.44,45 In this study, we aimed to evaluate the impact of a physician-delivered, disease-specific brief tobacco cessation intervention in diabetes care on the quitting rate, glycemic control, BP, and number of cigarettes smoked per day among patients with diabetes. The individually tailored intervention aims to help smokers who have diabetes to quit smoking.
Methods
Study design and participants
This RCT (ClinicalTrials.gov. NCT04864327) followed the CONSORT 46 guidelines. We aimed to evaluate the impact of a brief smoking cessation intervention on smoking cessation outcomes as well as on glycemic control and BP control among patients with diabetes. This RCT included patients with diabetes who smoked tobacco and who attended the outpatient diabetes clinic at Penang Hospital in Malaysia. Participants were randomly assigned to one of two study groups. The control group received routine diabetes care counseling and the intervention group received diabetes-specific brief tobacco cessation counseling in addition to routine diabetes care counseling.
Each participant completed a consent form indicating their agreement to take part in the study. The study was granted approval by the Medical Research Ethics Committee of the Ministry of Health, and the Clinical Research Centre at Hospital Pulau Pinang, Malaysia (NMRR-11-477-9538, 05-10-2011). Figure 1 illustrates the study design. All methods were carried out in accordance with relevant guidelines and regulations. The study was conducted between March 2012 and August 2013. Each patient was followed for three sequential visits, with 3 to 4 months between each visit. The medical records of patients included in the study were prospectively reviewed to extract the laboratory data.

Study design.
Patients were included in the study if they: (1) had a documented diagnosis of type 1 or type 2 diabetes mellitus; (2) were currently smoking tobacco (self-reported smoking of at least 100 cigarettes during the lifetime and smoking within the previous month as well as confirmation via biochemical measurement); and (3) spoke English and/or Malay.
Sample size and sampling method and randomization
The sample size needed for the RCT was calculated using the equation below:
47
For patients who provided their consent to be included in the trial, a researcher labeled the patient record with a numbered sticker for later identification. All numbers were then randomly assigned by the researcher to either the intervention or control group, using a computer-generated allocation procedure.
Description of brief tobacco cessation intervention for patients with diabetes
The tobacco cessation protocol consisted of performing a routine assessment (querying patients) of tobacco use, providing advice on the importance of quitting smoking, performing an assessment of the tobacco user’s readiness to quit, assisting in setting a quit date, and making arrangements for follow-up visits.48,49 This protocol is known as the 5A’s strategy. The intervention in this study was delivered by physicians who provided diabetes care to the participants and nurses who assisted during follow-up and monitoring. The physicians were specially trained in providing the tobacco cessation intervention via a workshop developed by the researchers. Physicians also received a booklet that provided specific information on counseling, which was adapted from tobacco cessation guidelines. Patients were counseled during each routine visit to the endocrine clinic (approximately every 3 to 4 months). For all patients, smoking status was checked using breath carbon monoxide (CO), and mean glycated hemoglobin (HbA1c) and BP measurements were taken.48–50 Physicians and researchers were not blinded to the group assignments, but participants were blinded to their group assignment. Prior to each participant’s visit, physicians received a brief refresher of the intervention from the researchers to limit bias.
Outcome measures
The primary outcome measures at each visit (every 3 to 4 months) included mean HbA1c, quitting rate (defined as the proportion of patients who had quit smoking tobacco at their second and/or final visit), BP, and mean number of cigarettes smoked per day. The secondary outcome measure involved the patient’s lipid profile (triglycerides, high-density lipoprotein, low-density lipoprotein, and total cholesterol). Smoking cessation (stopping smoking for the previous month) and smoking reduction (decrease the number of cigarettes smoked per day) were verified via a breath CO test as a biochemical measure, using the piCO+ Smokerlyzer (Bedfont, Harrietsham, Kent, England). 51 The cut-off values for the Smokerlyzer are 0.79% to 1.59% blood carboxyhemoglobin (COHb) or 0 to 6 CO parts per million (ppm) for non-smokers; any increment above these levels indicates a current smoker.
Data analyses
The collected data were analyzed using SPSS version 18.0 (SPSS Inc., Chicago, IL, USA). Descriptive and inferential statistics were used, as appropriate. To determine differences between the intervention and the control groups with respect to outcome measures (HbA1c, number of cigarettes smoked per day, BP, lipid profile, CO level), we used an independent t-test, Mann–Whitney U test, or Pearson’s chi-square test, as appropriate. To determine differences between the control and intervention groups in repeated time points, a mixed analysis of variance test was applied.52,53 The analyses were performed with 95% confidence intervals, and a p-value ≤0.05 was considered statistically significant.
Results
A total of 140 patients with diabetes who smoked tobacco were initially enrolled in the study. However, 14 participants were lost to follow-up for various reasons: seven participants relocated from Pulau Pinang, two died, three withdrew from participation, and two were excluded owing to incomplete data. Thus, 126 participants (63 in the intervention group and 63 in the control group) were included in the analyses. A modified CONSORT flow diagram is included in Figure 2. Most participants (approximately 95%) were men; approximately 41% of participants were Malay and the remainder were mostly Chinese and Indian (Table 1).

Modified CONSORT flow diagram for individual randomized controlled trials of nonpharmacologic treatments.
Demographic characteristics of the study population (N = 126).
As seen in Table 2, a non-significant difference between patients in the two groups was observed with respect to HbA1c and BP levels (systolic and diastolic). In general, a high mean HbA1c level was observed in the two groups over the three visits, based on normal reference values of the 2004 Malaysian clinical practice guidelines (7% to 9% indicates fair control). 54 However, the BP of patients in both groups was well controlled throughout the study period (<130/80 mmHg) and was within the normal BP range according to the Malaysian clinical practice guidelines normal reference values (Table 2). 54 A significant difference was observed in the number of cigarettes smoked per day between the two groups at the first two visits, suggesting better results in the intervention group than the control group (Table 2); however, the difference between groups was not significant at the final visit.
Outcome measures for tobacco cessation intervention among patients with diabetes.
SD, standard deviation; HbA1c, glycated hemoglobin; COppm, carbon monoxide level in parts per million; COHb, blood carboxyhemoglobin; TG, triglycerides; HDL, high-density lipoprotein; LDL, low-density lipoprotein.
*p-values calculated using independent t-test and significant (S) at <0.05.
**p-values calculated using Mann–Whitney U test and significant (S) at <0.05.
***p-values calculated using Pearson’s chi-square test and significant (S) at <0.05.
Table 2 presents the mean COppm and %COHb, used to categorize the study participants as low-frequency smokers or smokers, per the manufacturer’s guidelines. No significant differences were noted between patients in the two groups for the first two visits with respect to CO level. At the third visit, the control group had significantly lower CO concentrations than the intervention group (9.2 ± 6.0 ppm vs. 11.8 ± 6.9 ppm; p = 0.032). There was no significant difference between the two groups in terms of the quitting rate at 6 months. However, a favorable proportion of patients in both groups had reduced their cigarette consumption.
Discussion
Patients’ knowledge of how smoking cessation can affect diabetes control and slow diabetes complications is very important. In this study, providing patients with this knowledge did not motivate them to quit smoking after the intervention, suggesting that consistent and comprehensive intervention for a longer period may be necessary for patients with diabetes. The present study results can direct future research in this setting. Our findings regarding a decrease in the number of cigarettes smoked per day among all study participants can serve to enhance future efforts to improve quitting attempts and the success rate. 55 Previous studies have reported conflicting results. For instance, a study conducted in Indonesia reported a non-significant difference between patient groups with respect to the number of cigarettes smoked. 34 However, a study by Canga et al. 30 demonstrated results that were similar to those of the current study in which the mean number of cigarettes smoked daily showed significant differences in favor of the intervention group after 6 months. 30
It is assumed that smoking cessation is a major determinant of glycemic control, in addition to other measures for diabetes management. Participants’ glucose control did not differ over the study period within or between groups. It is possible that the duration of the study follow-up was insufficient to reveal a clear difference in glycemic control. We used a low-intensity intervention strategy comprising 5-minute brief smoking cessation advice delivered by a physician. A study in France reported a significant decrease in the glycated hemoglobin level and significantly improved BP among participants over the study period, as confirmed in repeated measures effects. 32 Because BP can exhibit changes faster than any other measure, several studies have shown that quitting smoking can lead to a sudden increment in BP rather than a decline;56–59 however, our study participants reduced the number of cigarettes smoked rather than quitting altogether, which was followed by BP improvement. 60 The lack of differences between the two groups may be related to random patient selection rather than according to patients’ willingness to stop smoking, as in the transtheoretical model of the stages of change. The Hokanson study yielded different results, with no differences in BP between participant groups over the study period. 33
Our patients’ CO levels decreased over the study period, which was consistent with the decrease in the number of cigarettes smoked daily. However, these results were not significant based on inferential analyses. The higher CO levels in the intervention group compared with the control group were consistent with the greater number of cigarettes smoked by the former group. A significant proportion of patients exhibited a reduction in the number of cigarettes smoked, but the number who succeeded in quitting was small. Furthermore, there was no difference in the quitting rate between the two groups, which may result from an absence of nicotine replacement therapy to boost the intervention effect and random selection of patients to the groups rather than according to their willingness to quit smoking. In this study, only four participants successfully quit smoking. Patients who were ready to stop smoking but could not achieve this on their own need advice so that they can consider their options and encouragement to make an effort to stop. However, owing to logistical issues (a long wait list), the smoking cessation clinic's assessment and follow-up arrangements were not completed as planned. An RCT in Spain reported opposite findings regarding differences in the quitting rate between participant groups; the rate of smoking cessation was 7.5-fold higher in the intervention group than that in the control group. 30 Findings similar to ours were reported in an RCT from Canada, with no differences between the intervention and control groups after 6 months, although a difference at the 3-month time point was observed. 33
No significant differences were observed between patients in the two groups with respect to their lipid profile (triglycerides, high-density lipoprotein, low-density lipoprotein, and total cholesterol) nor in repeated measures over the study period. Although patients in both groups exhibited improved total cholesterol at the end of the study, the improvement was not significant.
The main limitation of the present study was the use of the Smokerlyzer piCO+ to measure CO levels, for verification of tobacco cessation. This device cannot be considered as accurate as measuring urine cotinine levels because patients could inhale environmental CO from other sources that may give a false-positive result.
Conclusion
In the present RCT, participants in both the intervention and control groups reduced the number of cigarettes smoked per day over the study period. This finding can serve as a foundation for future studies on tobacco cessation interventions among patients with diabetes in Malaysia. Future research into more intensive counseling for these patients is highly recommended.
Supplemental Material
sj-pdf-1-imr-10.1177_03000605231208598 - Supplemental material for Impact of brief smoking cessation intervention on quitting rate and glycemic control in patients with diabetes: a randomized controlled trial
Supplemental material, sj-pdf-1-imr-10.1177_03000605231208598 for Impact of brief smoking cessation intervention on quitting rate and glycemic control in patients with diabetes: a randomized controlled trial by Albaroodi K.A. Ibrahim, Syed Azhar Syed Sulaiman, Ahmed Awaisu and Asrul Akmal Shafie in Journal of International Medical Research
Supplemental Material
sj-pdf-2-imr-10.1177_03000605231208598 - Supplemental material for Impact of brief smoking cessation intervention on quitting rate and glycemic control in patients with diabetes: a randomized controlled trial
Supplemental material, sj-pdf-2-imr-10.1177_03000605231208598 for Impact of brief smoking cessation intervention on quitting rate and glycemic control in patients with diabetes: a randomized controlled trial by Albaroodi K.A. Ibrahim, Syed Azhar Syed Sulaiman, Ahmed Awaisu and Asrul Akmal Shafie in Journal of International Medical Research
Footnotes
Acknowledgements
The authors would like to thank all physicians and endocrinologists at Hospital Pulau Pinang Endocrinology Clinic, especially Dr. Noor Azizah, head of the department, as well as all patients with diabetes who participated in and facilitated our work.
Authors' contributions
Albaroodi K.A. Ibrahim participated in the study design, data collection, data analyses, reporting of the results, and prepared the manuscript. Syed Sulaiman S.A. supervised the whole work. Awaisu A. participated in the study design and preparing the manuscript, Shafie A.A. supervised the data analyses. All authors read and approved the final manuscript.
Declaration of conflicting interests
The authors declare that there is no conflict of interest.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
References
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
