3.16 Smoking and diabetes

Last updated: June 2020
Suggested citation: Purcell, K, Greenhalgh, EM & Winstanley, MH. 3.16 Smoking and diabetes. In Scollo, MM and Winstanley, MH [editors].  Tobacco in Australia: Facts and issues. Melbourne: Cancer Council Victoria; 2020. Available from  http://www.tobaccoinaustralia.org.au/3-16-smoking-and-diabetes

 

3.16.1 Prevalence of diabetes in Australia

Diabetes mellitus (diabetes) is an umbrella term for a number of metabolic diseases that affect the body’s ability to control blood glucose levels; it is a disease marked by high blood glucose levels resulting from defective insulin production, insulin action or both. 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.1

There are three major types of diabetes: type 1 (sometimes referred to as ‘insulin dependent diabetes’), type 2 (sometimes referred to as ‘non-insulin dependent’ or ‘adult onset’ diabetes); and gestational diabetes. Type 1 diabetes most often occurs in childhood or young adulthood (though it can occur at any age) and is the result of low levels of or the inability to produce insulin. People with type 1 diabetes need insulin replacement for survival.1

Type 2 is the most common form of diabetes; it occurs mostly in people aged 40 years and over and is marked by reduced or less effective insulin. Although uncommon in childhood, it is becoming increasingly recognised in that younger age group.1 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.

An estimated 1.2 million (6%) Australian adults had diabetes in 2017–18, based on self-reported data from the 2017-18 data from the National Health Survey.2 This data is likely to  underestimate the prevalence of diabetes because it does not include people with undiagnosed diabetes. Data from the 2011–12 Australian Health Survey, which included both measured and self-report data found that for every four adults with diagnosed diabetes, there was one person who was undiagnosed.2 The prevalence of diabetes (based on self-reported data) among Australians has almost doubled from 3.3% in 2001 but has remained fairly stable since 2014–15. An estimated 1 million Australian adults (5%) had type 2 diabetes in 2017–18. There are currently no Australian national data that capture the prevalence of type 1 diabetes at all ages, but data is available for children. According to the National (insulin-treated) Diabetes Register (NDR), just over 6,500 children aged 0–14 had type 1 diabetes in 2017.2 It is estimated that one in seven pregnant women were affected by gestational diabetes in 2016-17.3 Type 2 diabetes was the 12th largest contributor to Australia’s disease burden in 2015, accounting for 2.2% of total burden of disease. There were 16,400 Australian deaths in 2015 due to diabetes, with half of these (55%) due to type 2 diabetes.4

Some population groups are at much higher risk for diabetes, notably Indigenous Australians, people born overseas, and those subject to the poorest socio-economic circumstances. Aboriginal and Torres Strait Islander adults were almost 4 times as likely to have diabetes compared with other Australians. Around 1 in 8 (13%) of Aboriginal and Torres Strait Islander adults (46,200 people) had diabetes, based on self-report and measured data from the ABS 2012–13 National Aboriginal and Torres Strait Islander Health Measures Survey.2 Aboriginal and Torres Strait Islander people are more likely to be hospitalised for diabetes and have higher death rates from diabetes than other Australians.2 Rates of diabetes, hospitalisations and/or mortality are also more common among overseas-born people from the South Pacific Islands, Southern Europe, Middle East, North Africa and Southern Asia. Diabetes prevalence and death rates for the most disadvantaged groups in the population are nearly twice as high as those in the most advantaged groups of the population.1

3.16.2 Causes of diabetes

Type 1 diabetes is an autoimmune disease that usually develops in childhood or early adolescence. The exact cause is unknown, but it is likely to result from interaction between genetic and environmental factors. A person with type 1 diabetes requires daily insulin replacement to survive, unless a successful pancreatic transplant occurs.2

Type 2 diabetes involves interaction between genetic components, environmental and lifestyle risk factors.2, 5 Lifestyle factors include physical inactivity, poor diet, overweight or obesity, and smoking. Type 2 diabetes is largely preventable through lifestyle changes. Type 2 diabetes can be managed with changes to diet and physical activity, oral glucose-lowering drugs, non-insulin injectable glucose-lowering medications, insulin injections, or a combination of these methods.2 

Gestational diabetes is characterised by glucose intolerance that develops during pregnancy. The risk factors for gestational diabetes are similar to those for type 2 diabetes: women are at higher risk if they are of relatively advanced age or obese when pregnant.2 It usually resolves after the birth but may reoccur in later pregnancies and is a significant risk factor for the development of type 2 diabetes in later life for the mother and child. Usually, gestational diabetes can be managed through lifestyle changes to diet and exercise, but some cases may require treatment with insulin or other medications.2

There is some evidence that depression can increase the risk of developing type 2 diabetes and diabetes complications. It is thought that the increased risk of type 2 may be due to elevated stress levels and weight gain. Poor foetal nutrition leading to low birthweight for gestational age may predispose some individuals to type 2 diabetes. If these individuals are exposed to other risk factors (such as obesity and physical inactivity) the likelihood of developing type 2 diabetes becomes greater.1 There are also a number of additional risk factors for diabetes complications, including high blood pressure, high blood cholesterol and tobacco smoking. The ‘metabolic syndrome’—the clustering of a number of risk factors including abdominal obesity, impaired fasting blood glucose, raised blood pressure, raised blood triglycerides and reduced blood HDL-cholesterol—substantially increases the risk of type 2 diabetes.1

The 2014 US Surgeon General’s report concluded that cigarette smoking is a cause of type 2 diabetes, with the risk of developing diabetes 30–40% higher for active smokers than non—smokers. The report highlights that reducing tobacco use should be promoted as a key public health strategy to prevent and control the increasing worldwide epidemic of diabetes.6 Further corroboration for the Surgeon General’s finding that smokers are more likely to develop type 2 diabetes than non-smokers has been provided in a 2007 systematic review7 and recent studies conducted in Japan,8 Korea,9, 10 China11 and the US.7

Since the release of the 2014 US Surgeon General’s report there has been increasing evidence that of the association between cigarette smoking, hyperglycemia, and the development of type 2 diabetes.12-16 A meta-analysis of 22 articles, representing 343,573 subjects and 16,383 patients with Type 2 diabetes found that cigarette smoking is associated with an increased risk of type 2 diabetes.17 A systematic review of seventeen articles including 20 prospective cohorts also found that smoking was associated with increased risk of type 2 diabetes and that female and male smokers had a similar risk of developing type 2 diabetes.18 A meta—analysis of 88 prospective studies found that smoking was associated with an increased risk of type 2 diabetes and estimated that 11.7% of the global cases of type 2 diabetes in men and 2.4% in women (i.e. about 27.8 million cases in total worldwide) could be attributable to active smoking.19

There is a positive dose dependent relationship between cigarette smoking and the risk of diabetes.6, 13, 16, 17, 19 A Japanese meta—analysis of 22 studies found a linear dose-response relationship between cigarette consumption and the risk of type 2 diabetes- the risk of type 2 diabetes increased by 16% for each increment of 10 cigarettes smoked per day.17 A US study found that smokers who smoked 20 cigarettes or more per day had a 79% higher incidence of diabetes mellitus compared with never smokers. The duration of smoking was also important, with smoking dose (per 10 pack-years) associated with a higher incidence of diabetes mellitus for black adults in the US.20

The mechanism by which smoking increases the risk of diabetes is uncertain.

Plausible biological mechanisms for this association include increased central obesity in smokers, increased inflammation and oxidative stress,6 increased insulin resistance, altered insulin secretion and other impairments to pancreatic function noted in smokers.7 It is also possible that genetic factors play a role in the association between smoking initiation and type 2 diabetes.21, 22

However, in contrast to the research studies above, a few studies have found no association between smoking and the risk of diabetes, suggesting the mechanism by which smoking influences diabetes may be very complex. A US multi—ethnic cohort study of 5,931 participants found no independent association between tobacco use and type 2 diabetes.23 A Chinese cross sectional study found that smokers have a lower prevalence of newly diagnosed diabetes mellitus than non-smokers among Chinese males with a lower BMI/ smaller waist.24 A limitation of the Chinese study could be recall bias of participants because data collection depended on memories of past smoking exposure.24 

There is also evidence that exposure to secondhand smoke is positively and independently associated with the risk of type 2 diabetes, from several observational studies conducted in the US,25, 26 Germany27 and Japan.28 A large meta—analysis19 and a Korean cross sectional study also found exposure to secondhand smoke was associated with a higher prevalence of  type 2 diabetes.29 Exposure to secondhand smoke as well as active smoking, is also a significant risk factors for carotid atherosclerosis in patients with type 2 diabetes.30 

3.16.3 Diabetic related health problems

As well as being life threatening in its own right, diabetes can also lead to a range of other serious health problems, including coronary heart disease, stroke, peripheral vascular disease, kidney disease, eye disease, and complications in pregnancy and childbirth.31 Smoking greatly increases the risk of pancreatic cancer in patients with diabetes mellitus and there is evidence that a combined risk of family history of pancreatic cancer, current smoking and current diabetes mellitus confers a 10-fold increase in risk of being diagnosed with this cancer.32, 33 Among male cancer survivors there is evidence that a history of smoking before diagnosis, obesity and insulin resistance increase the risk for several second primary cancers, indicating the need for screening for second primary cancers among cancer survivors with these risk factors.34 Smoking is related to low bone mass and increased risk of fracture in postmenopausal women in the general population, but recent evidence suggests that women with diabetes who are current smokers have more than a three-fold increase in risk of non-vertebral fractures than diabetic women who were never smokers.35

Diabetic complications are often classified as macrovascular complications (coronary artery disease, peripheral arterial disease and stroke) and microvascular complications (diabetic nephropathy, neuropathy, and retinopathy).5 Studies of people with diabetes consistently demonstrate that smokers have an increased risk of cardiovascular disease, premature death and microvascular complications of diabetes.5, 31 Among the lifestyle-related risk factors, smoking makes the largest contribution to the absolute risk of macrovascular complications for people with diabetes.5

There is a dose-dependent association between smoking and cardiovascular disease in individuals with type 1 diabetes. There is also an increased risk of stroke among men who are current or former smokers.36 A large cohort study in 20 countries of people with type 2 diabetes aged 55 years and over who were in cardiovascular risk, found that daily smoking was associated with an increased risk of all cancers, cardiovascular diseases and all—cause mortality. The hazards of smoking were similar between men and women except for major coronary events where there was some evidence of a stronger effect in women. Quitting smoking was associated with a 30% reduction in all—cause mortality. The longer the period of cessation, the greater the benefit.37 Among smokers with type 2 diabetes, a systematic review and meta-analysis of 89 cohort studies found that active smoking is associated with significantly increased risks of total mortality and cardiovascular events.38 Smoking cessation was associated with reduced risks for cardiovascular events compared to current smoking.38, 39 A large prospective study of 28,712 men and 30,700 women aged 25-64 years living in Finland confirmed that smokers with type 2 diabetes had higher all-cause mortality compared with non—smoking diabetics. The coronary heart disease mortality risk for smokers with type 2 diabetes was higher compared with non-smoking diabetics. The incidence of coronary heart disease was higher among current smokers compared with non—smoking diabetics. Cessation provided a some benefits with former smokers having a lower risk of coronary heart disease compared with current smokers but a higher risk than non—smoking diabetics.40

A cross-sectional study of 10,551 men and 15,297 Chinese women with diabetes found current smokers also have increased risk for poor glycemic control. There was a dose-response relationship between active smoking and the risk of poor glycemic control in men. Former smokers who quit smoking for less than 10 years remained at increased risk for poor glycemic control, with the risk declining after 10 years of smoking cessation to approximate that of non-smokers.41

Retinopathy (a form of eye disease) is a common microvascular complication of diabetes. A Swedish study of 794 people found that after an average of 17 years 67% of type 1 diabetics and 71% of type 2 diabetics, had developed diabetic retinopathy. Obesity, hyperglycemia and tobacco use predicted the onset of retinopathy between 9 and 17 years after diagnosis of diabetes. After 17 years, the number of diabetic patients with severe retinopathy was small.42 A meta—analysis of 73 studies on diabetic retinopathy (19 studies with type 1 and 56 studies with type 2 diabetes patients) found that compared with non-smokers, the risk of diabetic retinopathy significantly increased in smokers with type 1 diabetes while the risk significantly decreased in smokers with type 2 diabetes.43 A US study of type 1 diabetics found that smokers were at a higher risk of both retinopathy and nephropathy compared with former and never smokers. This study concluded that the negative association of smoking on glycemic control may be partially responsible for the adverse association of smoking on the risk of complications in type 1 diabetes including retinopathy.44

Nephropathy is a common complication of diabetes that causes end stage renal disease.45

The disease progresses from normal albuminuria to presence of microalbuminuria (traces of protein in the urine), then macroalbuminuria (protein in the urine), and finally renal insufficiency.46 Diabetic nephropathy arises from the impact of high blood glucose and blood lipid levels which increase oxidative stress and increase inflammation of renal structures.47 Smoking influences the development and progression of nephropathy in diabetics, possibly through a combination of effects on blood lipids and oxidative stress47 and its negative effects on glycemic control.44 

A meta-analysis of four prospective cohort, seven case-control, and eight cross-sectional studies found that smokers with type 2 diabetes had a significantly higher risk of having albuminuria compared with never smokers.48 Continuing to smoke and the duration of diabetes are two strong predictors of albuminuria in smokers with type 2 diabetes. Smokers with type 2 diabetes have 21% increased annual risk of albuminuria, compared to non-smokers.49 A 2017 meta—analysis of nineteen observational studies involving more than 78,000 participants and 17,832 diabetic nephropathy cases, found that smoking was an  independent risk factor for the development of diabetic nephropathy in patients with both type 1 and type 2 diabetes.50 A 2017 systematic review and meta—analysis of 21 studies also confirmed that smoking is a significant risk factor for nephropathy in diabetic patients.46 Another meta—analysis study in 2019 found that smoking was associated with an increased risk of developing diabetic nephropathy in patients with type 1 diabetes but the results for the association between smoking and type 2 diabetes were not statistically significant.45 A Korean cross—sectional study in 2016 found that adults who continue to smoke after a diagnosis of diabetes have a higher risk of developing diabetic nephropathy compared with diabetics who are non—smokers.47 Smoking is also a risk factor for the progression of diabetic nephropathy51 and the risk increases with the increasing dose of smoking.51, 52 Smoking cessation appears to have a beneficial effect, reducing complications associated with type 1 diabetes.44

Smoking is also a risk factor for developing diabetic foot ulcers and has a negative effect on the healing process.53, 54 A possible mechanism may be the smoking‐induced oxidative stress inside the cell. Smoking can also increase the severity of diabetic peripheral neuropathy,55 which can increase the risk of foot ulcers.53 Microvascular changes associated with smoking may also lead to tissue hypoxia and poor healing.53 A small case controlled study in 2016 suggested that the nerves of the lower limbs are more susceptible to diabetic complications compared with the upper limb and also confirmed that smoking is an independent factor for diabetic neuropathy.55 A 2018 meta—analysis of eight studies, including five cohort studies and three case control studies found that smoking significantly increased the risk of diabetic foot amputation compared with non-smoking diabetics. Smoking cessation is beneficial and appears to reduce the risk of diabetic foot amputation.56 

3.16.4 Smoking cessation and diabetes

There is systematic review evidence described previously in this chapter that confirms smoking increases the risk of developing type 2 diabetes. There is also evidence that the risk of developing diabetes is elevated in ex—smokers for several years following smoking cessation and declines over time.

A prospective study of middle-aged men and women found that adults who quit smoking experienced changes in their metabolic profile and had an increased risk for diabetes, at its highest 3 years after quitting, but still present 6 years after quitting. The increased risk may be partly associated with weight gain and systemic inflammation.57 A 2015 meta—analysis of 88 prospective studies19 found that ex—smokers had a higher risk of type 2 diabetes compared to never smokers, but a lower risk compared with current smokers, supporting the benefits of quitting smoking to reduce diabetes risk. Further analysis showed that the risk of developing diabetes in the long term was decreased by smoking despite the elevated risk in recent quitters.19 A 2015 study of 53,930 Japanese employees16 found that participants who had quit smoking less than 5 years before baseline had a similar risk of type 2 diabetes compared with those who continued smoking, but the risk decreased over time, and after 10 years was comparable to that of never smokers.16 A 2017 meta—analysis of 22 prospective studies confirmed that the risk of type 2 diabetes was high among those who quit smoking during the preceding 5 years. This risk decreased over time, reaching a risk level equivalent to that of never smokers after 10 years of sustained smoking cessation.17

Data from cohort studies in the US found that the risk of type 2 diabetes was higher among recent quitters (2 to 6 years since smoking cessation) than among current smokers. The risk peaked 5 to 7 years after quitting and then gradually declined. In this study, the short term increase in risk of type 2 diabetes was associated with weight gain, and the risk was not increased among quitters who did not gain weight.58

Some recent evidence suggests that among smokers with type 2 diabetes, smoking cessation can result in weight gain and a short-term worsening of some diabetic symptoms that may discourage smokers with diabetes from attempting to quit.59 A 2015 retrospective cohort study of more than 10,000 adult smokers with type 2 diabetes found that smoking cessation is associated with deterioration in glycaemic control within the first year of quitting, but as cessation continued glycemic control improved and became comparable to that of current smokers after 3 years. This change was unrelated to weight gain.60

Qualitative research with type 2 diabetic smokers found that satisfaction with current health status, lack of knowledge about type 2 diabetes and smoking, and misconceptions about cessation resulted in negative attitudes toward quitting. The quitting process was challenging, dealing with smoking among peer groups, psychological addiction and post-cessation weight gain key factors complicating the quitting process.61

This evidence underscores the need for smoking cessation to be accompanied by other strategies for diabetes prevention and early detection, as recommended in current clinical guidelines in the US and in Australia.31 

3.16.5 Conclusion

 In conclusion, cigarette smoking produces insulin resistance and chronic inflammation, which can accelerate macrovascular and microvascular complications, including retinopathy, neuropathy and nephropathy. Many clinical and experimental studies have found significant associations between cigarette smoking and development of diabetes, impaired glycaemic control, and diabetic complications (microvascular and macrovascular). A different lifestyle of smokers, in contrast to that maintained by non-smokers, may also contribute to these effects. The development of type 2 diabetes is yet another harmful consequence of cigarette smoking, and one that adds to the heightened risks of CVD; smoking cessation is crucial to facilitating glycaemic control and limiting development of complications.6


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References

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