Optimising cohort data in Europe

3. Main methodological challenges The field of cohort research has to overcome a number of challenges related to issues of different nature - methodological aspects associated with the main stages of the research, including stakeholders involvement, study design, data collection, data sharing (including harmonisation and integration), data access and availability, and sustainability of data infrastructures, as well as translational ELSI. A summary of these challenges is presented in Table 2.

Table 2. Challenges and obstacles in cohort research according to issue category

Issues

Challenges and obstacles

− Consortium of researchers of different countries. − Variations in jurisdictions, policies, cultural aspects, expectations about cohort data collection. − Participation of many disciplines (multidisciplinary team with many stakeholders from different organisations and areas of responsibility). − Complex logistic infrastructure, extensive financial resources/investment. − Big cohorts are not easy to establish (complex logistic infrastructure). − Significant time to mature (lengthy maturity rates of resources). − Significant amount of time for implementation of local approval procedures. − Extended time lags for data access and availability of EU based cohorts.

Involvement of a wide array of stakeholders

Temporality (harmonisation requires a considerable amount of time)

− Prospective cohort design is costly and time consuming. − Retrospective cohort design is more susceptible to biases.

Type of study

Definition and validation of variables

− Trade off and balance between precision and quantity. − Measurement differences over time.

− Data quality issues in ex post retrospective harmonisation methods (lack of appropriate documentation). − Lack of data documentation on the harmonisation process. − Differences in study designs and data collection for cultural reasons. − Lack of appropriate data identification in repository catalogues. − Differences in the extent to which data can be shared. − Lack of sustainable mechanisms for depletable data access (e.g. blood, serum). − Own procedures and rules of individual cohorts for organising access to their samples and data.

Harmonisation protocols and documentation

Data access and availability