European Heart Journal Advance Access originally published online on April 8, 2005
European Heart Journal 2005 26(17):1774-1782; doi:10.1093/eurheartj/ehi224
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Lifestyle and cardiovascular disease in middle-aged British men: the effect of adjusting for within-person variation
1Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London NW3 2PF, UK
2Department of Community Health Sciences, St George's Hospital Medical School, London, UK
Received 21 July 2004; revised 24 January 2005; accepted 17 February 2005; online publish-ahead-of-print 8 April 2005.
* Corresponding author. Clinical Trial Service Unit, Harkness Building, Radcliffe Infirmary, Oxford OX2 6HE, UK. Tel: +44 1865 557241; fax: +44 1865 558817.E-mail address: jonathan.emberson{at}ctsu.ox.ac.uk
Aims To examine the effect that within-person variation has on the estimated risk associations between cigarette smoking, physical inactivity, and increased body mass index (BMI) and the development of cardiovascular disease (CVD) in middle-aged British men.
Methods and results In total, 6452 men aged 40–59 with no prior evidence of CVD were followed for major CVD events (fatal/non-fatal myocardial infarction or stroke) and all-cause mortality over 20 years; lifestyle characteristics were ascertained at regular points throughout the study. A major CVD event within the first 20 years was observed in 1194 men (18.5%). Use of baseline assessments of cigarette smoking and physical activity in analyses resulted in underestimation of the associations between average cumulative exposure to these factors and major CVD risk. After correction for within-person variation, major CVD rates were over four times higher for heavy smokers (
40 cigarettes/day) compared with never smokers and three times higher for physically inactive men compared with moderately active men. Major CVD risk increased by 6% for each 1 kg/m2 increase in usual BMI. If all men had experienced the risk levels of the men who had never regularly smoked cigarettes, were moderately active, and had a BMI of 
25 kg/m2 (6% of the population), 66% of the observed major CVD events would have been prevented or postponed (63% before adjustment for within-person variation). Adjustment for a range of other risk factors had little effect on the results. Similar results were obtained for all-cause mortality.
Conclusion Failure to take account of within-person variation can lead to underestimation of the importance of lifestyle characteristics in determining CVD risk. Primary prevention through lifestyle modification has a great preventive potential.
Key Words: Cardiovascular disease • Lifestyle • Risk factors • Within-person variation