Abstract

Introduction
There is conflicting evidence on the link between bisphosphonates and stroke with studies variously showing increased, decreased or unchanged risk. We investigated the association between bisphosphonate treatment and the risk of stroke using a large routine clinical dataset.
Methods
We used a matched nested case-control study design analysing routinely collected electronic data from patients registered at primary care practices in England participating in the Royal College of General Practitioners Research and Surveillance Centre. Cases were patients aged 18 years or over, either living or dead, recorded as having had a stroke in the period 1st January 2005 to March 31st 2016. Each case was matched to one control according to age, sex, general practice attended and calendar time. Data were analysed using Stata, version 14.2. Conditional logistic regression was used to determine odds ratios for stroke according to bisphosphonate treatment and duration in cases compared with controls. We adjusted for disease risk groups, cardiovascular risk factors, treatments, smoking status, alcohol consumption, ethnicity , bisphosphonate types, fracture and socioeconomic status using IMD (Index of Multiple Deprivation).
Results
We included 31,414 cases of stroke with an equal number of matched controls. Overall, 83.2% of cases and controls were aged 65 years or older and there were similar proportions of females (51.5%) and males (48.5%). Bisphosphonate treatment was not associated with stroke after adjusting for the wide range of confounders considered (OR 0.86, 95% CI 0.62 - 1.19).
Conclusions
We found no association between bisphosphonate treatment and risk of stroke, after adjusting for other confounders.