Impact of potentially inappropriate prescribing on adverse health outcomes in older people attending general practice: a prospective cohort study
Potentially inappropriate prescribing (PIP) describes medications where risk generally outweighs benefit for older people. The Screening Tool for Older Person’s Potentially inappropriate Prescriptions (STOPP) consists of prescribing criteria developed through Delphi consensus and validated in several European countries. This is the first general practice study to investigate the longitudinal association of PIP, as defined by STOPP, with adverse drug events (ADEs), health related quality of life (HRQoL) and emergency department (ED) visits.
The STROBE guidelines were adhered to in the conduct of this study. Study design: Two year (2010-2012) prospective cohort study (n=904, ≥70 years, community-dwelling) with linked pharmacy dispensing data. Exposure: Baseline PIP: STOPP applied 12 months prior. Study outcomes: ADEs (patient interview and general practice (GP) medical record review), HRQoL (EQ-5D-3L: patient questionnaire) and ED visits (GP medical record review). Patient-reported ADEs were independently verified by dual academic GP review. Verified ADEs were then rated in terms of clinical severity, using a published classification system. Statistical analysis: Descriptive statistics, logistic (odds ratio (OR) (95% CI)), Poisson (incidence rate ratio (IRR) (95% CI) and linear regression models (regression co-efficient (95% CI)).
Of 791 participants eligible for follow-up, 673 (85%) returned a questionnaire and 605 (77%) also completed an ADE interview. For the primary outcome of ADE, a total of 286 (47%) were male. Median age was 79 years (Inter Quartile Range (IQR) 76, 83) with above average deprivation levels (median 1.36 (IQR -0.64, 2.88)). Baseline PIP prevalence was 42% and 445 (74%) patients reported ≥1 ADE at follow-up. The commonest drug classes and their associated ADEs were: i) antithrombotic agents (n=243, 41%) and easy bruising and indigestion/heartburn; ii) diuretics (n=162, 27%) and nocturia, urinary frequency and dry mouth; iii) beta-blockers (n=145, 24%) and cold hands and feet, fatigue and dizziness. The majority of ADEs were classified as mild in terms of clinical severity (95%). In multivariable analysis, ≥2 STOPP PIP was associated with ADEs (adjusted IRR: 1.29 (95% CI 1.03, 1.85; p=0.03); poorer HRQoL (adjusted regression co-efficient: -0.11 (95% CI -0.16, -0.06; p<0.001)); and, ≥1 ED visit (adjusted OR: 1.85 (95% CI 1.06, 3.24; p=0.03)).
Older community-dwelling people, prescribed ≥2 PIP, are more likely to report ADEs (≥2 PIP: adjusted IRR; 1.29 (95% CI 1.03, 1.60), p=0.03), clinically significant poorer HRQoL (≥2 PIP: EQ-5D score adjusted coefficient; -0.11 (95% CI -0.16, -0.06), p<0.001) and were almost twice as likely to attend the ED (≥2 PIP: adjusted OR 1.85 (95% CI 1.06, 3.24), p=0.03) during two year follow- up.