Swedish moist snuff and the risk of cardiovascular diseases

Sammanfattning: The snuff consumption in Sweden has increased substantially during recent decades and today more than every fifth male adult uses snuff daily. However, the evidence on health effects from long-term use of snuff is limited, especially regarding cardiovascular diseases. The overall objective of this thesis was to study the association between snuff use and cardiovascular diseases. Two epidemiological materials were used and both were restricted to men only. One material included a population based case-control study with 1 437 cases of myocardial infarction and 1 810 matched controls, aged 45-70 years and living in Stockholm or Västernorrland county between 1992 and 1994. The second material was a large nationwide cohort based on construction workers who attended at least one health check-up between 1978 and 1993. We found that snuff use was highly correlated with smoking and some cardiovascular risk factors. Furthermore, snuff users were generally younger than the non snuff users and there were geographical differences with a higher prevalence of snuff use in northern Sweden. To avoid confounding from smoking the main analyses were restricted to never smokers. We found no evidence that the snuff use increased the overall risk of myocardial infarction. In the large prospective cohort, consisting of more than 100 000 non-smoking construction workers, we observed an increased risk of fatal myocardial infarction among current snuff users compared to never users, the risk being even higher among heavy users, with relative risk estimates of 1.32 (95% CI, 1.08-1.68) and 1.96 (95% CI, 1.08-3.58), respectively. Furthermore, no increased overall risk of stroke was observed among the snuff users. However, the relative risk for fatal cases was 1.38 (95% CI 0.99-1.91) among current snuff users and for fatal ischemic stroke the relative risk was 1.72 (95% CI 1.06-2.78). For those who suffered non-fatal myocardial infarction or non-fatal ischemic stroke we found an increased mortality both overall and in cardiovascular diseases among snuff users compared to never tobacco users. We also found associations between snuff use and high blood pressure as well as hypertension. The prevalence of high blood pressure was significantly higher among snuff users than non-users at the time of first blood pressure measurement. During follow-up, snuff users who were normotensive at the first blood pressure measurement, had an increased risk of developing hypertension or high blood pressure at a subsequent measurement with relative risks of 1.36 (95% CI, 1.07-1.72) and 1.39 (95% CI 1.08-1.79), respectively. In conclusion, snuff use does not seem to increase the risk of myocardial infarction or stroke. However, an increased risk of fatal diseases was observed among snuff users, both for myocardial infarction and stroke, suggesting that snuff use could influence the severity of these outcomes. Snuff use was also associated with an increased risk for high blood pressure and hypertension.