A new data resource profile in the International Journal of Epidemiology describes the General Practice Database – Amsterdam, North Holland, Almere (GPD-ANHA). This large, dynamic cohort contains routinely collected primary care data and supports research aimed at improving the quality and delivery of primary care.

Data from more than 1.3 million individuals

GPD-ANHA was established in 2024 by integrating the general practice databases of the former Academic Medical Center and VU University Medical Center. The database contains data from more than 1.3 million individuals registered across over 160 general practices in Amsterdam, North Holland and Almere.

In 2024, 592,762 individuals were actively registered in the database. The median follow-up was 7.1 years overall and 10 years among actively registered individuals. The available data date back to 1996 and are updated quarterly.

Routine primary care data

The database includes information at the individual, consultation and general practice levels. Available data include demographics, diagnoses, prescriptions, referrals, laboratory results, vital signs and free-text consultation notes.

Before inclusion in GPD-ANHA, the data are pseudonymized and harmonized using a common data model. This allows longitudinal follow-up and facilitates linkage with other general practice networks, national registries and cohort studies. For example, linkage with the HELIUS cohortdata can add genetic and phenotypic information for participants included in both data sources.

Opportunities and limitations

The scale, length of follow-up and diversity of GPD-ANHA enable research into rare outcomes and populations that are often underrepresented in cohort studies, including people with migration backgrounds, non-native Dutch speakers and expatriates. Quarterly updates also allow researchers to examine changing public health issues and trends over time.

As the data are collected as part of routine care rather than specifically for research, some variables may be missing or recorded inconsistently. Clinical care provided outside the GPD-ANHA network is also not always captured. Linkage with complementary data sources can help address some of these limitations.

GPD-ANHA and its predecessor databases have supported more than 45 peer-reviewed publications. Researchers can request access to the data. Applications are assessed for scientific merit, feasibility and relevance to primary care.

Read the GDP-ANHA data resource profile in the International Journal of Epidemiology.