Cardiovascular disease risk factors in relation to smoking behaviour and history: a population-based cohort study

Abstract

Objective: To investigate how individual risk factors for cardiovascular disease (CVD) (blood pressure, lipid levels, body mass index, waist and hip circumference, use of antihypertensive or hypolipidemic medication, and diagnosed diabetes) differ in people aged 46 years with different smoking behaviour and history.

Methods: This population-based cohort study is based on longitudinal data from the Northern Finland Birth Cohort 1966 project. Data were collected at the 31-year and 46-year follow-ups, when a total of 5038 and 5974 individuals participated in clinical examinations and questionnaires. Data from both follow-ups were available for 3548 participants. In addition to individual CVD risk factors, Framingham and Systematic Coronary Risk Evaluation (SCORE) algorithms were used to assess the absolute risk of a CVD event within the next decade.

Results: The differences in individual risk factors for CVD reached statistical significance for some groups, but the differences were not consistent or clinically significant. There were no clinically significant differences in CVD risk as measured by Framingham or SCORE algorithms between never smokers, recent quitters and former smokers (7.5%, 7.4%, 8.1% for men; 3.3%, 3.0%, 3.2% for women; p<0.001).

Conclusions: The effect of past or present smoking on individual CVD risk parameters such as blood pressure and cholesterol seems to be of clinically minor significance in people aged 46 years. In other words, smoking seems to be above all an independent risk factor for CVD in the working-age population. Quitting smoking in working age may thus reduce calculated CVD risk nearly to the same level with people who have never smoked.

Figure 1

Selection of the study sample. Data from the 46-year follow-up were used to assess the relationship between smoking history and cardiovascular risk factors. Data from the 31-year and 46-year follow-ups were used to assess changes in smoking status, that is, determine the smoking history.

Figure 2

Absolute risk of a first cardiovascular event in the next decade as defined by the Framingham risk score. BMI was adjusted for when testing for differences between groups with different smoking histories. *p<0.001. BMI, body mass index.

Figure 3

Changes in smoking behaviour over time. Categories for this figure were generated as follows: (A) At the age of 31, the ‘non-smoker’ group includes all individuals who had never smoked. At the age of 46, the ‘non-smoker’ group includes individuals who had never smoked or who had quit smoking before the age of 31. (B) At the age of 31, the ‘quit smoking’ group includes participants who were ‘recent quitters’ or ‘former smokers’ at the time of evaluation. At the age of 46, the ‘quit smoking’ group includes those individuals who had smoked regularly at some point but had quit smoking between ages 31 and 46. (C) The ‘smoker’ group includes individuals identified as ‘current smokers’ at the time of evaluation.