Adverse drug reactions related hospital admissions in persons aged 60 years and over, The Netherlands, 1981-2007: less rapid increase, different drugs

Abstract

Background: Epidemiologic information on time trends of Adverse Drug Reactions (ADR) and ADR-related hospitalizations is scarce. Over time, pharmacotherapy has become increasingly complex. Because of raised awareness of ADR, a decrease in ADR might be expected. The aim of this study was to determine trends in ADR-related hospitalizations in the older Dutch population.

Methodology and principal findings: Secular trend analysis of ADR-related hospital admissions in patients ≥60 years between 1981 and 2007, using the National Hospital Discharge Registry of The Netherlands. Numbers, age-specific and age-adjusted incidence rates (per 10,000 persons) of ADR-related hospital admissions were used as outcome measures in each year of the study. Between 1981 and 2007, ADR-related hospital admissions in persons ≥60 years increased by 143%. The overall standardized incidence rate increased from 23.3 to 38.3 per 10,000 older persons. The increase was larger in males than in females. Since 1997, the increase in incidence rates of ADR-related hospitalizations flattened (percentage annual change 0.65%), compared to the period 1981-1996 (percentage annual change 2.56%).

Conclusion/significance: ADR-related hospital admissions in older persons have shown a rapidly increasing trend in The Netherlands over the last three decades with a temporization since 1997. Although an encouraging flattening in the increasing trend of ADR-related admissions was found around 1997, the incidence is still rising, which warrants sustained attention to this problem.

Figure 1. Adverse Drug Reactions, annual number and age-standardized rates per 10,000 persons aged ≥60 years in the Netherlands, 1981–2007.

Separate regression lines are fitted to the period 1981–1996 (blue) and the period 1997–2007 (red). Solid lines indicate regression lines fitted to data points for the corresponding time period; dashed lines indicate the regression lines extrapolated for the remaining time period. Error bars indicate the 95% confidence interval.

Figure 2. The composition of drug groups causing Adverse Drug Reactions related hospital admissions in persons aged ≥65 years in the Netherlands (1981–2007).

The ICD-9 codes for Adverse Drug Reactions are shown. The main drug groups causing ADR-related admissions are shown separately in this figure. *“Other” drug groups were less frequently seen (<2% per group) and includes ICD-9 codes: E936-E338, E940, E941, E943, E945, E946, E948 and E949. The distribution changed during the study (p<0.001, Chi ²-test).