3.16 Smoking and diabetes
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Diabetes is an umbrella term for a number of metabolic diseases that affect the body's ability to control blood glucose levels. The hormone insulin is produced in the pancreas, and helps the body use glucose for energy. If insulin production or the effectiveness of an individual's insulin is impaired, then diabetes may result.88
There are three major types of diabetes. Type 1 diabetes most often occurs in childhood or young adulthood, and is the result of low levels of or the inability to produce insulin. About 10–15% of diabetics in Australia have Type 1 diabetes. Type 2 diabetes, also known as diabetes mellitus, is more likely to occur in adulthood and is caused by lowered effectiveness of insulin. This is by far the most common form of diabetes, accounting for up to 90% of incidence in the population. Gestational diabetes, the onset of diabetes in pregnancy, occurs in a small proportion of otherwise unaffected women and is usually transient, although women who develop gestational diabetes have a higher risk of developing Type 2 diabetes later in life.88
Diabetes is estimated to affect about 950,000 Australians aged 25 or above, or almost 8% of the population.28 Some population groups have a higher incidence of diabetes than others, including Indigenous Australians, and individuals of Melanesian, Polynesian, Chinese or Indian origin.88
Being overweight, having high blood pressure, having high blood cholesterol levels, eating an unbalanced diet and physical inactivity are major risk factors for developing Type 2 diabetes.88 As well as being life-threatening in its own right, diabetes can lead to a range of other serious health problems, including coronary heart disease, stroke, peripheral vascular disease, kidney disease, eye disease,89 and complications in pregnancy and childbirth.90
Smokers with Type 1 and Type 2 diabetes are at increased risk of illness and premature death, mostly through development of cardiovascular disease, but other disease processes associated with diabetes may also be made worse by smoking.91, 92 Smokers with Type 1 diabetes in particular may have a higher risk of developing kidney disease, and possibly eye and nerve damage as well, whereas smokers with Type 2 diabetes are more likely to increase their risk of coronary heart disease, stroke and peripheral vascular disease.93
Evidence is also accumulating that shows that smoking is associated with an elevated risk of developing Type 2 diabetes.93–99 A major review and meta-analysis of published data has found that current smokers are more likely to develop diabetes than ex-smokers and never smokers, and that smokers of 20 or more cigarettes a day are at greater risk than lighter smokers.100 Overall, current smokers are estimated to have a 44% greater risk, and ex-smokers a 23% greater risk of developing Type 2 diabetes than people who have never smoked.100 Plausible biological mechanisms for this association include increased insulin resistance, altered insulin secretion and other impairments to pancreatic function noted in smokers.100 According to the authors of this review, 'the relevant question should no longer be whether this association exists, but rather whether this established association is causal.'100 p2660 If further research proves a causal relationship between smoking and Type 2 diabetes, it can be expected to have a major impact on future estimates of tobacco-caused morbidity and mortality in Australia and globally.
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