Review

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Diabetes Metab J 2012;36:399-403
http://dx.doi.org/10.4093/dmj.2012.36.6.399
pISSN 2233-6079 · eISSN 2233-6087 DIABETES & METABOLISM JOURNAL

Smoking and Type 2 Diabetes Mellitus

Sang Ah Chang
Division of Endocrinology and Metabolism, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea

Cigarette smoking is a well-known risk factor in many diseases, including various kinds of cancer and cardiovascular disease.
Many studies have also reported the unfavorable effects of smoking for diabetes mellitus. Smoking increases the risk of developing
diabetes, and aggravates the micro- and macro-vascular complications of diabetes mellitus. Smoking is associated with insulin re-
sistance, inflammation and dyslipidemia, but the exact mechanisms through which smoking influences diabetes mellitus are not
clear. However, smoking cessation is one of the important targets for diabetes control and the prevention diabetic complications.

Keywords: Diabetes complications; Diabetes mellitus; Smoking

INTRODUCTION This review is about the various smoking effects on diabetes

mellitus, diabetic complications, and diabetic incidence. Un-
Smoking is one of the modifiable risk factors for many chronic derstanding the hazardous effects of smoking on diabetes mel-
diseases, such as cardiovascular disease (CVD), cancer, chron- litus may lead to more emphasis on smoking prevention and
ic obstructive lung disease, asthma, and diabetes. However, the smoking cessation as important strategies in the management
adverse effects of smoking on diabetes have been generally un- of diabetes mellitus.
der recognized. In the guidelines from the Korean Diabetes
Association, smoking cessation is recommended as one of the SMOKING AND DIABETES INCIDENCE
most important steps in preventing the cardiovascular com-
plications of diabetes [1]. Many studies have shown that the There is much evidence that smoking increases the risk of dia-
adverse effects of smoking on diabetes mellitus are not only betes. Several cohort studies in Korea have reported that smok-
diabetic macrovascular complications but the causal nature of ing was associated with an increased risk for the development
its association with diabetes and the progression of diabetic of diabetes. Cho et al. [6] followed 4,041 men for 4 years in ru-
microvascular complications has yet to be explored. ral and urban settings in Korea, and found that past and cur-
Although smoking is known to decrease body weight, it is rent smokers had a significantly increased risk for type 2 dia-
associated with central obesity [2]. Smoking also increases in- betes, and the risk increased with the number of cigarettes
flammation and oxidative stress [3], to directly damage β-cell smoked. Another study reported a 14-year-long prospective
function [4] and to impair endothelial function [5]. cohort study, in which the risk of diabetes among men and
The prevalence of smoking in Korean men is near 50%, which women who smoked 20 cigarettes or more per day was 1.55
is the highest smoking rate in the Western Pacific region. In (95% confidence interval [CI], 1.51 to 1.60) compared to those
addition to obesity, the high prevalence of smoking is one of who never smoked [7].
the major health problems for Korea’s public health. A Japanese study reported similar results of a positive cor-

Corresponding author: Sang Ah Chang This is an Open Access article distributed under the terms of the Creative Commons At-
Division of Endocrinology and Metabolism, Department of Internal tribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/)
Medicine, St. Paul’s Hospital, The Catholic University of Korea College of which permits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Medicine, 180 Wangsan-ro, Dongdaemun-gu, Seoul 130-709, Korea
E-mail: sangah@catholic.ac.kr
Copyright © 2012 Korean Diabetes Association http://e-dmj.org
 Chang SA

relation between cigarette consumption and risk for diabetes cholesterol levels, and an increased proportion of small dense
[8]. The health professionals’ follow-up study demonstrated low density lipoprotein particles. Fibrinogen levels and plas-
that the risk for diabetes among men who smoked ≥25 ciga- minogen activator inhibitor 1 activity were also elevated in
rettes per day was 1.94 (95% CI, 1.25 to 3.03) [9]. Another Brit- smokers [18].
ish study showed the risk for diabetes in smoking men was In terms of glucose homeostasis, smoking has a negative ef-
around 1.7, after adjusting for confounding factors, such as fect on glucose control. In a population-based prospective
age, body mass index, physical activity, alcohol intake, social study, cigarette smoking was positively associated in a dose
class, and antihypertensive treatment [10]. dependent manner with elevated HbA1c after adjustment for
There have been few studies on the effect of smoking on the possible confounding by dietary variables [19]. This finding
risk of diabetes in women as generally the prevalence of smok- was also reported in patients with diabetes in Sweden; smok-
ing is lower in women than men. However, the results from ing type 1 and type 2 patients had a higher mean HbA1c but a
the Nurses’ Health Study in the United States (114,247 women, lower mean body mass index than non-smokers [20].
1,227,589 person-years follow-up) showed that the risk for di-
abetes in smokers was 1.42 after adjustment for other risk fac- SMOKING AND DIABETIC
tors [11]. MICROVASCULAR COMPLICATIONS
The same cohort was followed for 16 years, and a new anal-
ysis was performed. The predictable risk factors for diabetes The smoking effects on microvascular diabetes complications
were overweight and obesity, as in men, low physical activity, a vary across reports. Generally, several studies have shown that
poor diet, current smoking, and abstinence from alcohol were smoking has an adverse effect on diabetic nephropathy, but the
all independently associated with the risk for diabetes. The ad- influence of smoking independently with glucose control, on
justed risk for diabetes in smokers was 1.4 compared with retinopathy and neuropathy are unclear.
non-smokers [12].
SMOKING AND NEPHROPATHY
THE EFFECT OF SMOKING ON INSULIN
ACTION Several studies have demonstrated that smoking promotes di-
abetic microalbuminuria and exacerbates diabetic nephropathy.
The exact mechanism for why smoking increases the risk of In the study by Biesenbach et al. [21], a 13-year follow-up study,
diabetes and deteriorates glucose homeostasis has not been the progression of nephropathy was clearly increased in smok-
fully elucidated, but the available evidence shows that smoking ers. The authors showed that smoking was a risk factor for dia-
increases insulin resistance. betic kidney disease, independent of age, sex, and duration of
In healthy young men, acute smoking showed an increased diabetes and HbA1c levels.
insulin resistance [13]. Smokers had a significantly increased In prospective studies by Chuahirun and Wesson [22] and
homeostatic model assessment insulin resistance index an hour Chuahirun et al. [23], the adverse effects on diabetic neprhrop-
after smoking [14]. The smoking reduced insulin mediated athy in type 2 patients were confirmed, even in optimal hyper-
glucose uptake by 10% to 40% in men who smoked compared tensive patients.
with non-smoking men [15,16]. In type 2 diabetic subjects, in-
sulin and C-peptide responses to oral glucose load were sig- SMOKING AND RETINOPATHY
nificantly higher in smokers than non-smokers and the insulin
resistance, as determined by the euglycemic clamp technique, The association of smoking and diabetic retinopathy has not
was positively correlated in a dose dependent manner [17]. been clear. It was reported that retinopathy has been associat-
Thus smoking induced insulin resistance in patients with type ed with glycemic control and not smoking state [24]. Some
2 diabetes, as well as healthy subjects. studies have reported no association with smoking and reti-
In addition to increased insulin resistance, smoking also nopathy in type 2 diabetes [24,25]. The United Kingdom Pro-
showed dyslipidemia prone to atherosclerosis. Smokers had spective Diabetic (UKPD) study to determine risk factors re-
higher fasting triglycerides and lower high density lipoprotein lated to the incidence and progression of diabetic retinopathy

400 Diabetes Metab J 2012;36:399-403 http://e-dmj.org

Smoking and diabetes mellitus

followed patients over 6 years from diagnosis. The development Recently, a meta-analysis in the Asia-Pacific region, in men
of retinopathy was associated with glycemia and higher blood with diabetes, the hazard ratio comparing current smokers with
pressure, but not smoking [26]. Thus in type 2 patients, the ef- non-smokers was 1.42 for CHD. In Asia, where there are high
fects of smoking on diabetic retinopathy has not been as clear rates of smoking, and a rapidly increasing prevalence of diabe-
as with nephropathy. tes, the author concluded that cigarette cessation strategies
there were huge benefits in terms of reducing the burden of
SMOKING AND NEUROPATHY CVD in men with diabetes [35].

There are few studies about smoking and diabetic neuropathy. SMOKING AND STROKE
Smoking may affect diabetic neuropathy differently according
to the type of diabetes [27]. In type 2 diabetic patients, smok- Smoking also increases the risk of stroke in patients with dia-
ing was not a risk factor in the presence of polyneuropathy or betes, but may not be as strong as CHD. In the UKPD study,
sensory neuropathy as diagnosed by symptom and sign [27,28]. mathematical models were developed to estimate the risk of
It was reported that there was no relationship between current stroke, and the variables were smoking, duration of diabetes,
or previous levels of smoking and the severity and duration of age, sex, systolic blood pressure, total cholesterol to high den-
chronic painful neuropathy [29]. But in the study by Tamer et sity lipoprotein cholesterol ratio, and presence of arterial fi-
al. [30], while smoking was not associated with neuropathic brillation [36]. In a study using the general practice research
complaints, using electromyography-supported neuropathy database in the United Kingdom, smoking was an additional
examination there were significant relationships with smok- risk factor for stroke in type 2 diabetic patients [37]. Another
ing, as well as HbA1c. Therefore, more studies are needed to 4-year prospective study, also showed that smoking and HbA1c
evaluate the association between smoking and neuropathy. were predictors of stroke among the type 2 diabetic patients
without a history of a previous stroke [38].
SMOKING AND MACROVASCULAR The relative risk of smoking for stroke has not been as high
COMPLICATIONS as that for CHD. In the Nurses’ Health Study, in smokers who
smoked 1 to 14 cigarette per day, the risk was significant for
Smoking has been shown to be a significant risk factor for all- CHD but not for stroke. In those who smoked 15 cigarettes or
cause mortality, and for mortality due to CVD and coronary more per day, the relative risk for CHD and stroke were 2.68
heart disease (CHD) in diabetics. Smokers die on average 8 to and 1.84, respectively [33]. Similar trends were shown in a
10 years younger than non-smokers, as age is entered into most Swedish study, in which the relative risk of smoking was high-
multi-regression analysis. er in myocardial infarction (2.33) than for stroke (1.12) in 30
to 59 year-old patients [39].
SMOKING AND CHD
CONCLUSIONS
Smoking is a major risk factor for CVD in non-diabetic sub-
jects, as well as diabetic subjects. In an 8-year prospective There have been many studies showing that smoking has
study, smoking was significantly associated with an increased harmful effects on patients with diabetes. Smoking increases
risk for CHD in diabetic patients [31]. The UKPD study clear- diabetic incidence and aggravates glucose homeostasis and
ly showed that smoking was a significant and independent risk chronic diabetic complications. In microvascular complica-
factor for CHD in type 2 diabetic patients [32]. In the Nurses’ tions, the onset and progression of diabetic nephropathy is
Health Study, in women with type 2 diabetes, it was demon- highly associated with smoking. In macrovascular complica-
strated that cigarette smoking was associated in a dose-depen- tions, smoking is associated with a 2 to 3 times higher incidence
dent manner with an increased mortality and CHD. Compared of CHD and mortality. However, smoking prevention and
with never-smokers, the relative risks for CHD were 1.66 for smoking cessation may not be emphasized enough in diabetic
current smokers of 1 to 14 cigarette per day, and 2.68 for cur- clinics. Thus, educating patients on the importance of not
rent smokers of 15 or more cigarettes per day [33,34]. smoking and engaging in smoking cessation programs are im-

http://e-dmj.org Diabetes Metab J 2012;36:399-403 401

 Chang SA

portant strategies for the management of diabetes. Study. Smoking as a modifiable risk factor for type 2 diabetes
in middle-aged men. Diabetes Care 2001;24:1590-5.
CONFLICTS OF INTEREST 11. Rimm EB, Manson JE, Stampfer MJ, Colditz GA, Willett WC,
Rosner B, Hennekens CH, Speizer FE. Cigarette smoking and
No potential conflict of interest relevant to this article was re- the risk of diabetes in women. Am J Public Health 1993;83:
ported. 211-4.
12. Hu FB, Manson JE, Stampfer MJ, Colditz G, Liu S, Solomon
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