What Are the Effects of Varenicline Compared With Nicotine Replacement Therapy on Long Term Smoking Cessation and Clinically Important Outcomes?

• Status: Unknown status
• Trial end date: 2019-09-30
• Target enrollment: 0
• Participant gender: All

Summary

Introduction: Smoking is a major avoidable cause of ill-health and premature death. Treatments that help patients successfully quit smoking have an important effect on health and life expectancy. Varenicline is a medication that can help smokers successfully quit smoking. However, there are concerns that it may cause adverse effects, such as increase in the occurrence of depression, self-harm and suicide and cardiovascular disease. In this study the investigators aim to examine the effects of varenicline versus other smoking cessation pharmacotherapies on smoking cessation, health service use, all-cause and cause-specific mortality and physical and mental health conditions.

Methods: In this project the investigators will investigate the effects of varenicline compared to nicotine replacement therapies on: (1) long-term smoking cessation and whether these effects differ by area level deprivation; and (2) the following clinically-important outcomes: rate of general practice and hospital attendance; all-cause mortality and death due to diseases of the respiratory system and cardiovascular disease; and a primary care diagnosis of respiratory illness, myocardial infarction or depression and anxiety. The study is based on a cohort of patients prescribed these smoking cessation medications from the Clinical Practice Research Datalink (CPRD). The investigators will use three methods to overcome confounding: multivariable adjusted Cox regression, propensity score matched Cox regression, and instrumental variable regression. The total expected sample size for analysis will be at least 180 000. Follow-up will end with the earliest of either an 'event' or censoring due to the end of registration or death.

Ethics and dissemination: Ethics approval was not required for this study. This project has been approved by the CPRD's Independent Scientific Advisory Committee (ISAC). The investigators will disseminate the findings via publications in international peer-reviewed journals and presentations at international conferences.

• Accepts Healthy Volunteers?: No

Details

• Lead Sponsor: University of Bristol
• Treatments: Nicotine; Varenicline

Criteria

Inclusion Criteria:

Patients:

• With CPRD records aged 18 and over.

• Who were prescribed medicines in BNF category 4.10.2 from 1st September 2006, when varenicline was introduced to the UK, to the present.

• With records that were classified as 'acceptable' by the CPRD from all up to standard practices at least 18 months prior to date of entry of each cohort (1st March 2005).

• Who have data defined as "acceptable" by the CPRD if they meet minimum quality control standards, for example their registration period with their GP is valid. "Up to standard" practices are GP practices defined by the CPRD to be providing data of sufficient quality for research purposes.

Exclusion Criteria:

• Patients who registered at a practice less than 365 days before the first recorded prescription to allow for high quality assessment of baseline data and possible confounders.

• Patients prescribed bupropion in the year before their index prescription will be excluded from the analysis. It is relatively rare for patients to be prescribed both NRT and varenicline on the same day. In the investigators' previous study this only occurred for 0.248% of all prescription events. In the primary analysis for this study the investigators will exclude patients initially prescribed both NRT and varenicline.

Follow-up

• Follow-up will end with the earliest of either an "event" or censoring due to the end of registration or death.