There are scientific reports in the literature that smokers are at increased risk of developing type 2 diabetes as well as developing the conditions underlying diabetes, i.e. insulin resistance and impaired glucose tolerance. Recent studies have begun to examine the specific relationship between snus use and type 2 diabetes.
Diabetes occurs when there is an imbalance in the levels of glucose and insulin in the body. Two precursor conditions underlie this disease and are frequently studied in conjunction with diabetes. Impaired glucose tolerance refers to a condition in which blood glucose levels are higher than normal but not high enough to qualify the individual as diabetic. Insulin resistance is a condition in which target tissues in the body gradually become insensitive to the natural actions of insulin. Type 2 diabetes is the most common form of diabetes, and occurs when a patient’s tissues become resistant to insulin.
Important research results on Swedish snus:
- One cross-sectional study of the relationship of snus use to risk factors for heart disease suggests that it is linked to an increase in insulin levels. Three other studies do not support this finding.
- One cross-sectional study suggests that snus use is linked to an increased prevalence to type 2 diabetes. The results from this study are uncertain and the association has not been confirmed in analytic studies
- In a prospective analytic cohort study that generated both prevalence and incidence data, snus use was not associated with an increased risk of type 2 diabetes.
- In an experimental study acute use of snus had no effect on the insulin function.
Insulin resistance - a risk factor of cardiovascular disease.
The relationship of snus use and insulin resistance has been described in four descriptive studies on risk factors for cardiovascular disease. Three of the studies found no statistically significant associations between snus use and insulin reactivity or plasma insulin levels (Bolinder, 1997; Eliasson et al., 1995; Wallenfeldt et al., 2001). The fourth study suggested that serum insulin levels may be significantly higher in snus users compared to non-tobacco users (Eliasson et al., 1991).
Type 2 diabetes.
Three studies describe the relationship between snus use and insulin resistance or impaired glucose tolerance as it underlies diabetes. The strongest of these studies (Eliasson et al., 2004) Examined the effect of snus use and smoking on the risk of developing type 2 diabetes among 3384 men in a population based cross-sectional and prospective follow-up study (the Northern Sweden MONICA Study). At the onset of the study the prevalence of clinically diagnosed diabetes was significantly higher among current and ex-smokers compared to non-tobacco users. On the other hand the prevalence was not increased among snus users. The prevalence of pathologic glucose tolerance was not significantly elevated among snus users or smokers at the onset of the study. The risk of developing diabetes under the follow-up time period was increased among smokers and ex-smokers but not among those who used snus exclusively. The authors concluded that snus users do not have an increased risk of developing diabetes. This study is the first study in which prospective data show that snus use is not associated with the same increased risk of diabetes as smoking.
In contrast to the results from the study above, the results from a descriptive study by Persson et al. (2000) suggested that an association exists between snus use and type 2 diabetes. This cross-sectional study examined a cohort of Swedish men, half of whom had a strong family history of diabetes. The results showed that exclusive users of snus had approximately a 4-fold increased prevalence of type 2 diabetes compared to never users of tobacco. However, this finding must be viewed with caution because the risk estimate was based on only four cases of diabetes among snus users. Additional results also indicated that exclusive snus users did not experience impaired glucose tolerance and that snus users did not experience increased insulin resistance, conditions which are recognized precursors to diabetes. An important limitation of cross-sectional studies is that they can’t address causal relationships, i.e. if snus use causes diabetes. Analytic studies such as the study by Eliasson et al. (2004) do not suffer from this limitation. Attvall et al. (1993) studied acute effects of smoking and snus use on the insulin resistance in a group of healthy habitual smokers. They found that smoking but not snus use causes insulin resistance.
Attvall, S., Fowelin, J., Lager, I., Von Schenk, H., and Smith, U. 1993. Smoking induces insulin resistance – a potential link with the insulin syndrome. J. Int. Med. 233: 327-332. Bolinder, G., Norén, A., Wahren, J., and de Faire, U. 1997. Long-term use of smokeless tobacco and physical performance in middle-aged men. Eur. J. Clin. Invest. 27:427-433. Eliasson, M., Asplund, K., Evrin, P.E., and Lundblad, D. 1995. Relationship of cigarette smoking and snuff dipping to plasma fibrinogen, fibrinolytic variables and serum-insulin: The northern Sweden MONICA study. Atherosclerosis 113:41-53. Eliasson, M., Asplund, K., Nasic, S., and Rodu, B. 2004. Influence of smoking and snus on the prevalence of type 2 diabetes amongst men: the northern Sweden MONICA study. J. Int. Med. 256: 101-110. Persson, P.-G., Carlsson, S., Svanström, L., Östenson, C.-G., Efendic, S., and Grill, V. 2000. Cigarette smoking, oral moist snuff use and glucose intolerance. J. Int. Med. 248: 103-110. Wallenfeldt, K., Hulthe, J., Bokemark, L., Wikstrand, J., Fagerberg, B. 2001. Carotid and femoral atherosclerosis, cardiovascular risk factors and C-reactive protein in relation to smokeless tobacco use or smoking in 58-year-old men. J. Int. Med. 250: 492-501.