Recruitment rate too low (COVID-19 pandemic), end of funding

People with diabetes still smoke at equivalent rates as non-diabetics. There is lack of evidence regarding interventions for smoking cessation among individuals with diabetes. The aim of this project is to assess the 12 months efficacy of a smoking cessation intervention tailored to diabetes and gender specificities, in a population of 500 smokers with type 2 diabetes. The secondary objectives are to assess the impact of smoking cessation on anthropometric outcomes, diabetes control and renal function and fecal microbiota.

Smoking and diabetes are both major public health burden. They act synergistically on morbidity and mortality. Micro and macro-vascular complications are dramatically increased among diabetic smokers; however people with diabetes still smoke at equivalent rates as non-diabetics. There is lack of evidence regarding interventions for smoking cessation among individuals with diabetes and the small number of existent studies has yielded mixed results.

The aim of this project is to assess the 52 weeks (12 months) efficacy of a smoking cessation intervention tailored to diabetes and gender specificities, in a population of smokers with type 2 diabetes.

The secondary objectives are to assess the impact of smoking cessation on anthropometric outcomes, diabetes control and renal function.

The exploratory objectives are to assess the impact of smoking cessation on fecal microbiota The nested sub-study's exploratory objectives are to explore the associations between social stigma and diabetes, and mental health and diabetes.

The study design is an open label, randomized controlled trial with a nested cross-sectional study.

Participants will be recruited from the Policlinique Médicale Universitaire (PMU) of Lausanne, the university hospital in Lausanne (CHUV) and peripheral hospitals, private practices of general internists and specialists of diabetology and the community.

All screening procedures will be performed by a study nurse delegated by the PI based at the PMU. Eligible participants will be randomly allocated to either the intervention or control arm. Stratified randomization by sex will be done to ensure that the proportion of men and women is the same in both arms. Demographic data, medical data and specific questionnaires related to diabetes, smoking, gender and mental health /social stigma will be administered at baseline and a blood sample will be taken. In a subsample of 80 selected participants change in microbiota in stool will be measured at baseline, 3, 8 and 26 weeks after smoking cessation (or after baseline for continuing smokers).The intervention group will have 4 individual counseling sessions over 12 weeks. The control group will have 1 counseling session and will be given written information on smoking cessation. The control group will receive 2 telephone calls at 3 weeks and 8 weeks and a control visit at 12 weeks to assess smoking cessation (without counseling). Both groups will have a follow-up visit at 26 weeks and at 52 weeks.

500 participants in total will be included, 250 in each intervention arm. The duration of the study is planned for 3 years ( 4-5 participants/week during 2 years and follow-up of 52 weeks).

For the main outcome the analyses will be performed intention to treat. Participants lost to follow-up will be considered as smokers. The primary outcome (52 weeks smoking abstinence) will be compared using Pearson's chi-squared tests.

Power calculations indicate that a sample size of approximately 400 people is needed to detect a 10% difference in smoking abstinence between intervention and control groups (52 weeks continuous smoking abstinence equal to 0.2 in the intervention group and 0.1 in the control group) with a two-sample proportions test using Pearson's chi-squared test, power 80%, significance level 0.05. With an expected 20% attrition rate, the sample will be increased to 500 participants.

This study will be conducted in compliance with the protocol, the current version of the Declaration of Helsinki, the ICH-GCP as well as all national legal and regulatory requirements.

Inclusion Criteria:

• Informed Consent as documented by signature;
• Having smoked > 100 cigarettes during his/her entire life and currently smoking cigarettes (no minimal threshold);
• Having been diagnosed with a type 2 diabetes;
• Being ≥ 18 years old;
• Speaking and understanding French

Exclusion Criteria:

• Not being able to give an informed consent and follow the procedure of the study (due to dementia, psychological disorder, language problem);
• Being pregnant or breastfeeding;
• Being enrolled in another smoking cessation study or program or in a multi-behavioral program including smoking cessation;
• Enrolment of the investigator or other research collaborators, their family members, employees and other dependent persons;
• Planning to move out of Switzerland within the next year.

Identification is based on self-representation of gender eligibility with the possibility to self identify as transgender.

According to the article 18 of the LRH, participants will not be given the full information regarding the main purpose of the study (assess the efficacy of a smoking cessation trial) in order not to influence participants regarding the intervention and also to decrease selection bias (only smokers motivated to quit would take part and thus induce a selection bias). Methodologically, such a blinding to procedure would allow a better assessment of its efficacy. Furthermore, risks associated to the intervention are considered as very low. Participants will be informed a posteriori once they have completed the study or before in case they remove their consent or quit the study.

The outcome assessor will be a research collaborator independent of the study nurse who performed the intervention and blinded to the intervention.