Self-reported physical activity and cardiovascular biomarkers in an adult population

Physical activity is a complex and multidimensional behaviour and the measurement of physical activity is a major challenge. The self-report questionnaire is feasible and easy to administer, but the self-report nature of the measurement makes validity a crucial issue. Abstract til Mette Aadahls ph.d.-afhandling fra 2007.



Kontakt Mette Aadahl
Mette Aadahl på Fag og Forsknings ph.d.-liste

Abstract af Mette Aadahl

Background

There is convincing evidence that physical inactivity is a strong and independent risk factor for cardiovascular disease and that regular physical activity reduces cardiovascular and all-cause mortality. However, the dose-response relationship between physical activity level and cardiovascular biomarkers is not fully understood and it is unclear how vigorous intensity activity and inactivity, respectively, are related to cardiovascular biomarkers. Physical activity is a complex and multidimensional behaviour and the measurement of physical activity is a major challenge. In epidemiological research physical activity level is usually measured by self-report questionnaire, when the relationship between physical activity level and disease status is explored. The self-report questionnaire is feasible and easy to administer, but the self-report nature of the measurement makes validity a crucial issue.

Aims

The aims of this thesis were: 1) to validate a self-report physical activity questionnaire against objectively measured maximal oxygen uptake 2) to explore the dose-response relationship between total daily physical activity level, as measured by the new physical activity questionnaire, and biological CVD risk factors: anthropometric measures, serum lipids and blood pressure and 3) to explore whether amount of self-reported TV-viewing and vigorous intensity activity had different impacts on anthropometric measure, serum lipids and blood pressure.

Methods

The study population comprised two sub samples of participants from the Inter 99 study, a population-based randomised controlled trial, investigating the effect of a non-pharmacological intervention on cardiovascular disease and diabetes. The Inter 99 study was initiated in 1999 and the initial study population consisted of 61.301 men and women between 30 and 60 years of age, living in Copenhagen County and obtained through the Danish Civil Registration System.

Study population I: A total of 1693 men and women, 33-63 years of age, from the three-year follow-up of the Inter 99 study comprised the study populations in the present cross sectional study. Study population II: A total of 102 volunteer men and women, 35-65 years of age, recruited from the five-year follow-up of the Inter 99 study comprised the study population in the validation study. Inter 99 participants were given a health examination including a self-administered questionnaire on physical activity and other life style habits, a physical examination, blood tests, and an individual IHD risk assessment using the computer programme PRECARD®. Volunteer participants from the five-year follow-up undertook a test of maximum oxygen uptake. Statistical analyses were carried out using multiple linear regression analyses.

Results

Amount of self-reported daily vigorous physical activity was positively associated with maximum oxygen uptake (p=0.0001), whereas total amount of physical activity was not associated with maximum oxygen uptake. Overall self-reported physical activity level was inversely associated with waist circumference (men p=0.012, women p=0.011), BMI (p=0.0004), waist hip ratio (p=0.002) and triglycerides (p=0.0001), and positively associated with HDL (p

Conclusion

The physical activity questionnaire used in this study has acceptable validity, since amount of selfreported daily vigorous activity reflected maximum oxygen uptake in adult men and women. This study suggests a linear dose-response relationship between physical activity level and certain biological cardiovascular risk factors up to a threshold of a daily 24-hour activity level of 45 METs. TV-viewing and vigorous physical activity should be regarded as separate types of behaviour that relate to different biological cardiovascular disease risk factors.

 

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