The Inter99 Study

Inter99 is a population based randomised intervention study which took place at the Research Centre for Prevention and Health. The study is based on 61,301 persons in certain age groups, living in the south western part of The Capital Region of Denmark. The aim of the study was to prevent cardiovascular disease by healthy lifestyle. A random sample was invited for screenings of the risk of cardiovascular disease and repeatedly offered assistance to improve their lifestyle, while another random sample, the control group, completed questionnaires.


Cardiovascular diseases is the most dominating cause of morbidity and mortality in the Danish population, and researchers have estimated that ¾ of the cases can be explained by the lifestyle factors: smoking, physical inactivity and unhealthy diet.

The purpose of the Inter99 study is to investigate whether an individual intervention towards smoking, unhealthy diet and physical inactivity can change morbidity and mortality from cardiovascular diseases and type 2 diabetes (and other lifestyle related diseases) in a whole population. The study is the first large study making it possible to draw valid conclusions.

The first part of the Inter99 study was carried out in the period 1999-2006. A large population based group (13,016 persons) of randomly selected people aged 30-60 years was invited for a health examination and lifestyle counselling. Furthermore, persons in the high intensity group A, at high risk of cardiovascular disease, were offered participation in smoking cessation groups or/and diet-exercise groups.

Persons at high risk of cardiovascular disease got repeated offers of health examination, counselling and participation in groups after 1 and 3 years. All participants were re-examined after 5 years and all participants received questionnaires after 10 years.

A randomised sample (N=5,264) of the remaining 48,285 persons were followed with questionnaires in the five year period – to observe spontaneous changes in lifestyle in the general population. The whole study population of 61,301 persons is followed through central registers to evaluate the consumption of health care services, medicine, development of diseases and changes in social conditions.

Inter99 is the largest scientific prevention study on lifestyle in Denmark ever.


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