Original ResearchThe Association between Smoking and Depression in a Canadian Community-Based Sample with Type 2 Diabetes
Introduction
Diabetes mellitus is a progressive chronic illness currently affecting approximately 8% of Canadians (1), and its progression can lead to the development of both micro- and macrovascular complications (2). Two factors associated with diabetes are tobacco smoking and depression 3, 4. Studies in the general population find a consistent and strong bidirectional association between depression and smoking (5); therefore, exploring these elements is important within this population, given both are linked with adverse outcomes in people with diabetes. Both smoking and depression are associated with acceleration of diabetes-related complications 3, 6, poor glycemic control 7, 8 and overall increased risk of morbidity and mortality 9, 10. Furthermore, smoking cessation is a key goal in diabetes self-care guidelines, and depression has been linked with poor adherence to self-care regimens in people with diabetes (11). Given the similar outcomes shared between smoking and depression, it is not surprising that previous studies often find a significant association between smoking and depression in people with diabetes; however, these studies have several limitations. Many studies treat smoking as a binary variable 12, 13, and thus may be missing crucial information with regards to this complex behaviour. One previous study was based on small clinical samples and may therefore not be generalizeable (14). A more recent study (15) failed to control for potentially confounding factors related to the presence of diabetes. Therefore, to address these limitations, the current study aims to investigate the associations between multiple levels of smoking and depression in a community-based sample of people with diabetes. The specific objectives of the current study were to (1) report on prevalence and associations of smoking across socio-demographic, lifestyle and disease-related factors and (2) determine whether smoking status was independently associated with major depression when controlling for a variety of potential confounding variables, using a community-based sample with type 2 diabetes.
Section snippets
Methods
This study is based on data from the Diabetes Health and Well Being Study (DHS), a population-based telephone survey of the noninstitutionalized adult population in Quebec, Canada. Participants were recruited between January and April 2008 through random selection of listed phone numbers in Quebec by a recognized polling firm, Bureau d'Intervieweurs Professionnels (Montreal, Quebec, Canada). Inclusion criteria were being 18 to 80 years of age, have a diagnosis of diabetes determined by a
Results
In the present study, lifetime prevalence of smoking within the sample was 62.9%; current smoking prevalence of the population was 20.5%; among those currently smoking, 62.4% were moderate/heavy smokers.
Table 1 presents the socio-demographic variables and smoking status. Those in the 18–49 age bracket were more likely to be current smokers, whereas those 65–80 were more likely to be never smokers. Females were more likely to be never smokers (44.6% vs. 28.6%), whereas men were most likely to be
Discussion
In the present Canadian community-based study in people with type 2 diabetes, heavy smokers were over twice as likely to have major depression compared to never smokers. This association remained significant even when controlling for socio-demographic characteristics, diabetes characteristics and complications, disability, other chronic illness, alcohol use and physical activity. Our study adds to existing literature by demonstrating that A) smoking is strongly associated with major depression,
Author Disclosure
All authors declare no conflict of interest. The study was supported by grants from the Canadian Institute of Health Research (CIHR).
Author Contributions
MC and KS wrote the manuscript that KS, NS and GG critically revised. All authors contributed to the conception and design of the manuscript. NS collected the data. MC conducted the analysis, with assistance from KS and GG. All authors approved the final version to be published.
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