The information content of the registers used in the study and the time period during which the information is used are described in more detail below.
During the follow-up, the survey data, information from the health check-ups as well as information on sickness absence, sociodemographic factors and residential areas in the personnel register of the City of Helsinki will be combined on those research participants who have given their informed consent for the linkage. The information will be combined with computers of the University of Helsinki. In addition, during the follow-up, permission to use and to combine register information with the survey and health check-up data are requested from the register holders (the National Institute for Health and Welfare, Kela, the Finnish Centre for Pensions and Statistics Finland). A separate application with the research plan is submitted to each register data holder. The information is mainly combined with a computer of the University of Helsinki. The persons whose information is registered have been informed that the register information will be combined with the survey and the check-ups performed by an occupational health nurse. Information is requested and combined with the survey responses only if the respondents have given their informed consent for combining the information.
In the register study section of the Helsinki Health Study, information in the personnel register of the City of Helsinki is combined with information obtained from other registers. In this case, the survey responses are not used.
The module files of the study are
1. Address register, content: name, work address, home address and social security number.
2. Survey. In the baseline phase, data were collected in three phases in 2000, 2001 and 2002. The first follow-up survey was conducted in 2007 and the following surveys in 2012 and 2017 (for the new cohort, the 2017 survey is the baseline survey).
3. Information collected at health check-ups for specific age groups performed by occupational health nurses. Collection of this information started in January 2000 and ended in the beginning of 2003.
4. Information in the personnel register of the City of Helsinki. The City has shared register data with the project starting from 1990. In the future, information will be requested annually for as long as the project is ongoing.
5. Register information from the register data holders. Information is requested mainly starting from 1990 until the end of the follow-up (until 2025, when the need for further follow-up will be re-assessed).
National Institute for Health and Welfare: Care Registers for Social Welfare and Health Care (HILMO), the Finnish Cancer Registry
Kela: information on prescribed and reimbursed prescription medicines purchases, information on rights for special reimbursement for medicines and information on daily sickness benefits and rehabilitation with diagnoses.
The Finnish Centre for Pensions: information on pensions started. In addition: Reasons for incapacity. Negative pension decisions and pre-decisions on employment pension and rehabilitation (type of pension, pension sector and pensions act, date of the adoption of the decision, reason for the rejection, diagnoses for disability pensions)
Statistics Finland: mortality and causes of death, education, socioeconomic status, occupational status and information on employment and income.
The time period during which the information is used
The register information is combined with the survey both retrospectively (time before answering the survey) and during the follow-ups (after answering the survey). Retrospective information is important because health and functional capacity is also explained by socioeconomical status, earlier state of health and sickness absence.
The information is combined with survey responses based on permissions requested separately from the register data holders for the period during which the information is recorded in the registers. The follow-up continues until 2025, after which the need for further follow-up is re-assessed. During the follow-up, updates to the register data are obtained from the register data holders once a year or once in two years.
At the moment, the above-mentioned information is available, and will be combined with the survey data based on informed consent, from the following time periods:
1. Personnel register of the City of Helsinki: 1990–2014
2. National Institute for Health and Welfare: Care Registers for Social Welfare and Health Care (HILMO) years 1990–2014, the Finnish Cancer Registry 1953–2014
3. Kela: years 1990–2014
4. The Finnish Centre for Pensions: years 1990–2014
5. Statistics Finland: years 1990–2014