Effect of screening and lifestyle counselling on incidence of ischaemic heart disease in general population: Inter99 randomised trial

Abstract

Objective: To investigate the effect of systematic screening for risk factors for ischaemic heart disease followed by repeated lifestyle counselling on the 10 year development of ischaemic heart disease at a population level.

Design: Randomised controlled community based trial.

Setting: Suburbs of Copenhagen, Denmark.

Participants: 59,616 people aged 30-60 years randomised with different age and sex randomisation ratios to an intervention group (n = 11,629) and a control group (n = 47,987).

Intervention: The intervention group was invited for screening, risk assessment, and lifestyle counselling up to four times over a five year period. All participants with an unhealthy lifestyle had individually tailored lifestyle counselling at all visits (at baseline and after one and three years); those at high risk of ischaemic heart disease, according to predefined criteria, were furthermore offered six sessions of group based lifestyle counselling on smoking cessation, diet, and physical activity. After five years all were invited for a final counselling session. Participants were referred to their general practitioner for medical treatment, if relevant. The control group was not invited for screening.

Main outcome measures: The primary outcome measure was incidence of ischaemic heart disease in the intervention group compared with the control group. Secondary outcome measures were stroke, combined events (ischaemic heart disease, stroke, or both), and mortality.

Results: 6091 (52.4%) people in the intervention group participated at baseline. Among 5978 people eligible at five year follow-up (59 died and 54 emigrated), 4028 (67.4%) attended. A total of 3163 people died in the 10 year follow-up period. Among 58,308 without a history of ischaemic heart disease at baseline, 2782 developed ischaemic heart disease. Among 58,940 without a history of stroke at baseline, 1726 developed stroke. No significant difference was seen between the intervention and control groups in the primary end point (hazard ratio for ischaemic heart disease 1.03, 95% confidence interval 0.94 to 1.13) or in the secondary endpoints (stroke 0.98, 0.87 to 1.11; combined endpoint 1.01, 0.93 to 1.09; total mortality 1.00, 0.91 to 1.09).

Conclusion: A community based, individually tailored intervention programme with screening for risk of ischaemic heart disease and repeated lifestyle intervention over five years had no effect on ischaemic heart disease, stroke, or mortality at the population level after 10 years.Trial registration Clinical trials NCT00289237.

Fig 1 Flow chart of randomised Inter99 study showing distribution and participation of 59 616 people in various groups during four contacts (baseline, one year, three years, and five years) over five year period. IHD=ischaemic heart disease. *59 993 people were drawn for study population, but 377 emigrated, died, changed their personal identification number, or disappeared before baseline, leaving 59 616. †Random sample of control group (n=5264) received questionnaires. ‡1308 people were randomly allocated to low intensity intervention group; this intervention group was only used to investigate whether lower intensity intervention was effective to achieve changes in lifestyle (described in detail in appendix 1); this group is not included in endpoint analyses, as power calculations were based on large high intensity intervention group, as shown in this figure (for fuller flow chart including low intensity intervention group see www.Inter99.dk)

Fig 2 Cumulative incidence curves of 10 year incidence of ischaemic heart disease (IHD), stroke, combined events (IHD, stroke, or both), and total mortality in intervention and control groups