Debunking the 'only 50%' myth: Prevalence of established risk factors in New Zealanders with self-reported ischaemic heart disease

Abstract

Objective: To estimate the prevalence of established risk factors for ischaemic heart disease (IHD) in New Zealand adults and compare the prevalence in adults with and without this disease. Design: Data were obtained from the 2002/03 New Zealand Health Survey. Risk factor prevalence was determined by: self-reported doctor diagnosis of high blood pressure, high cholesterol and diabetes; self-report of smoking and physical inactivity; and measurement of obesity. Presence of IHD was based on self-report of heart disease (doctor diagnosed at age 25 years or over) together with current medical or past surgical treatment for this disease. Multiple logistic regression was used to determine prevalence rate ratios (PRRs) for males and females separately, adjusting for age, ethnicity and deprivation. Results: The overall prevalence of IHD was 8%. Overall risk factor prevalences were in the range of 20-25% for each of high blood pressure, high cholesterol, smoking, obesity and physical inactivity, and approximately 5% for diabetes. Overall, 94-97% of adults with IHD had at least one risk factor (depending on how smoking was defined). The PRRs of IHD were highest for cholesterol (about 4.5), followed by blood pressure (about 2.3), with all other risk factors around 1.5. PAF estimates indicate that 80-85% of IHD was attributable to the presence of at least one risk factor for all age, gender and ethnic groups. Conclusions: Established risk factors account for 80-85% of the non-fatal burden of IHD in New Zealand. Limited research resources would be better used to evaluate which interventions are effective and efficient at reducing exposure of all population groups to known risk factors, rather than on identification of additional risk factors.