There are a number of risk factors for heart disease. Many of them are within our control, for example, a healthy diet and being physically active. Others we cannot change, such as age or having a family history of heart disease. Of the risk factors for which we are responsible, like smoking, the association with the heart is still being uncovered. New research indicates that the influence smoking has on the heart may come, at least in part, from its likelihood of increasing a person's risk of diabetes or glucose intolerance.
The CARDIA (coronary artery risk development in young adults) study began in 1985 and included 15 years of follow-up. Those selected to participate were adults with no glucose intolerance at the start of the study. Participants were separated into four categories based on self-reported tobacco smoke exposure. Of these participants: 1386 reported being current smokers, 621 were previously smokers, 1452 had never been smokers but had regular exposure to secondhand smoke (as confirmed by blood test), and 1113 were never smokers and had no exposure to secondhand smoke. The median age at the start of the study was 25. Follow-ups were then conducted by researchers at the 2, 5, 7, and 15-year marks.
Researchers found that after 15 years smokers were at the most significant risk of developing glucose intolerance, and subsequently diabetes. They also found that those exposed to tobacco smoke passively were at an increased risk despite not being smokers themselves. Toxins found in the blood of passively exposed persons were similar to those found in the blood of current smokers but in different levels. Interestingly, some toxins were even more concentrated in the blood of passively exposed persons due to how these toxins are produced at different temperatures.
One such toxin has been hypothesized to be directly toxic to the pancreas. This toxicity might explain the heightened risk in the secondhand smoke exposure group despite their less overall exposure as compared to the current smoker group. The likelihood of developing glucose intolerance or diabetes was lowest in the non-smoking, unexposed group even after adjustments have been made for a variety of glucose sensitivity risk factors. This means that although smoking may be a marker for other unhealthy behaviors, those behaviors were adjusted for and therefore not responsible for the increase in risk noted by researchers.
The study is significant as it reiterates the dangers of smoking. Furthermore, it underscores the idea that smoking is not just a risk factor for smokers themselves but also to those exposed to their toxic cocktail second hand. In addition, it highlights the link between smoking and diabetes, a condition not generally associated with smoking and a risk factor for heart disease. Although the numbers are unlikely to persuade a smoker to quit smoking for their benefit, it is possible these results will convince a person to quit because of the health risks they pose to those they regularly encounter. If someone you love smokes, feel free to remind them of their risk to your health, often, and backed with the facts of this study.
Sources: British Medical Journal, National Heart, Lung and Blood Institute