The Clinical Practice Research Datalink (CPRD) is an ongoing primary care database of anonymised medical records from general practitioners, with coverage of over 11.3 million patients from 674 practices in the UK. With 4.4 million active (alive, currently registered) patients meeting quality criteria, approximately 6.9% of the UK population are included and patients are broadly representative of the UK general population in terms of age, sex and ethnicity. General practitioners are the gatekeepers of primary care and specialist referrals in the UK. The CPRD primary care database is therefore a rich source of health data for research, including data on demographics, symptoms, tests, diagnoses, therapies, health-related behaviours and referrals to secondary care. For over half of patients, linkage with datasets from secondary care, disease-specific cohorts and mortality records enhance the range of data available for research. The CPRD is very widely used internationally for epidemiological research and has been used to produce over 1000 research studies, published in peer-reviewed journals across a broad range of health outcomes. However, researchers must be aware of the complexity of routinely collected electronic health records, including ways to manage variable completeness, misclassification and development of disease definitions for research.

Treatment with oral corticosteroids is known to decrease bone density but there are few data on the attendant risk of fracture and on the reversibility of this risk after cessation of therapy. A retrospective cohort study was conducted in a general medical practice setting in the United Kingdom (using data from the General Practice Research Database [GPRD]). For each oral corticosteroid user aged 18 years or older, a control patient was selected randomly, who was matched by age, sex, and medical practice. The study comprised 244,235 oral corticosteroid users and 244,235 controls. The average age was 57.1 years in the oral corticosteroid cohort and 56.9 years in the control cohort. In both cohorts 58.6% were female. The most frequent indication for treatment was respiratory disease (40%). The relative rate of nonvertebral fracture during oral corticosteroid treatment was 1.33 (95% confidence interval [CI], 1.29–1.38), that of hip fracture 1.61 (1.47–1.76), that of forearm fracture 1.09 (1.01–1.17), and that of vertebral fracture 2.60 (2.31–2.92). A dose dependence of fracture risk was observed. With a standardized daily dose of less than 2.5 mg prednisolone, hip fracture risk was 0.99 (0.82–1.20) relative to control, rising to 1.77 (1.55–2.02) at daily doses of 2.5–7.5 mg, and 2.27 (1.94–2.66) at doses of 7.5 mg or greater. For vertebral fracture, the relative rates were 1.55 (1.20–2.01), 2.59 (2.16–3.10), and 5.18 (4.25–6.31), respectively. All fracture risks declined toward baseline rapidly after cessation of oral corticosteroid treatment. These results quantify the increased fracture risk during oral corticosteroid therapy, with greater effects on the hip and spine than forearm. They also suggest a rapid offset of this increased fracture risk on cessation of therapy, which has implications for the use of preventative agents against bone loss in patients at highest risk.