Objective: To determine whether nicotine replacement therapy (NRT) is associated with an increased risk of acute myocardial infarction, acute stroke, or death.
Design: Self control case series analysis of data from The Health Improvement Network (THIN) to estimate the relative incidence of myocardial infarction and stroke in four 14 day periods before and after the first prescription for NRT.
Setting: THIN is a computerised general practice database.
Subjects: Patients contributing data to THIN.
Interventions: Observational study of NRT.
Main outcomes: Acute myocardial infarction, acute stroke, and death.
Results: 33 247 individuals had been prescribed NRT, of whom 861 had had a myocardial infarction and 506 a stroke. There was a progressive increase in the incidence of first myocardial infarction in the 56 days leading up to the first NRT prescription (overall incidence ratio 5.55, 95% confidence interval (CI) 4.42 to 6.98), but the incidence fell after this time and was not increased in the 56 days after starting NRT (incidence ratio 1.27, 95% CI 0.82 to 1.97). The results were similar for second myocardial infarction and stroke, and for subgroups of people with pre-existing angina and hypertension. There were 960 deaths in our cohort during a mean follow up period of 2.6 years after starting NRT, with no evidence of an increased mortality in the 56 days after the NRT prescription (incidence ratio 0.86, 95% CI 0.60 to 1.23).
Conclusions: The use of NRT is not associated with any increase in the risk of myocardial infarction, stroke, or death.
- myocardial infarction
- nicotine replacement therapy
- case-series method
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Sources of funding: British Lung Foundation and the Wellcome Trust.
Competing interest statement: The division of Statistics at the Open University is in receipt of a CASE PhD studentship partly funded by GlaxoSmithKline. In the past John Britton has received sponsorship from GlaxoSmithKline and Richard Hubbard has received sponsorship from Bayer to attend international respiratory medicine conferences, but both have declined all such sponsorship for the last five years. John Britton has received an honorarium from a third party organisation but originating from GlaxoSmithKline for speaking at an invited conference on smoking cessation management guidelines in 2002 and has acted as a consultant to several companies involved in smoking cessation therapies. There are no other competing interests for any of the other authors.
Ethics approval: The study protocol for this paper was reviewed and approved by the GPRD Scientific and Ethical advisory Group.
Work attributed to: Division of Epidemiology and Public Health, Nottingham University.
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