Elsevier

Preventive Medicine

Volume 48, Issue 1, January 2009, Pages 74-78
Preventive Medicine

No interaction of body mass index and smoking on diabetes mellitus risk in elderly women

https://doi.org/10.1016/j.ypmed.2008.10.008Get rights and content

Abstract

Objective

We sought to assess the interaction of smoking and body mass index (BMI) on diabetes risk.

Methods

We analyzed data from a community-based prospective cohort of 41,836 women from Iowa who completed a baseline survey in 1986 and five subsequent surveys through 2004. The final analysis included 36,839 participants.

Results

At baseline (1986), there were 66% never smokers, 20% former smokers, and 14% current smokers. Subjects represented 40% normal weight, 38% overweight, and 22% obese individuals. Compared to normal weight women, the hazard ratio (HR) for diabetes was increased in overweight (HR 1.96; 95% CI 1.75–2.19) and obese subjects (HR 3.58; 95% CI 3.19–4.02). The hazard ratio for diabetes increased in a dose-dependent manner with smoking intensity. Compared to never smokers, former smokers had a higher risk for diabetes (HR 1.22; 95% CI 1.11–1.34). Among current smokers, the hazard ratio for diabetes was 1.21 (95% CI 0.95–1.53) for 1–19 pack-year smokers, 1.33 (95% CI 1.12–1.57) for 20–39 pack-year smokers, and 1.45 (95% CI 1.23–1.71) for ≥ 40 pack-year smokers. Similar trends were observed when the results were stratified by BMI. A test of interaction between BMI and smoking on diabetes risk was not statistically significant.

Conclusions

Our findings suggest that smoking increases diabetes risk through a BMI-independent mechanism.

Introduction

Cigarette smoking, overweight, and obesity constitute significant modifiable risk factors for cardiovascular disease and subsequent mortality (Gregg et al., 2005, Thom et al., 2006). From 1997–2001, smoking contributed to 137,979 annual deaths in the United States from cardiovascular disease (Centers for Disease Control and Prevention, 2005). Cigarette smoking and overweight are also risk factors for diabetes, the fourth leading cause of mortality in the United States (Heron, 2007, Willi et al., 2007, Mokdad et al., 2003).

Cigarette smokers typically weigh less than non-smokers (Flegal et al., 1995). However, smokers frequently use cigarettes to control their weight (Klesges et al., 1997), and weight gain after smoking cessation is associated with smoking relapse (Borrelli and Mermelstein, 1998). Consequently, overweight and obese smokers may possess a heightened risk for diabetes if smoking and BMI act synergistically to increase the risk for diabetes (Mokdad et al., 2003).

The Nurses Health Study observed a higher relative risk for diabetes mellitus among female smokers with a BMI > 29 (Rimm et al., 1993). Other findings suggest that BMI does not modify the association between smoking and diabetes (Will et al., 2001). Determination of an interaction between smoking and BMI on diabetes risk may enhance understanding of the risk for diabetes among overweight and obese smokers and improve counseling of smokers on their diabetes risk.

This study uses population-based survey data from the Iowa Women's Health Study (IWHS) to assess the BMI-stratified impact of smoking on the risk for diabetes mellitus in a cohort of elderly women. We hypothesized that cigarette smoking contributes to diabetes risk independent of BMI.

Section snippets

Methods

The Iowa Women's Health Study (IWHS) is a prospective cohort study of 41,836 women aged 55–69 years at enrollment in 1986. Details of the cohort characteristics have been described previously (Folsom et al., 1990). In 1986, a 16-page questionnaire was mailed to 99,286 randomly selected women and returned by 41,836 women (41.9% response rate). Follow-up questionnaires (response rates) were mailed in 1987 (91%), 1989 (90%), 1992 (83%), 1997 (79%) and 2004 (69%). The cohort was followed for

Results

We based the results on a maximum of 18 years and 487,013 person-years of follow-up. Mean follow-up was 13.2 years. Our cohort included 36,839 women with a mean baseline age of 62 years. Baseline smoking status included 24,265 (66%) never smokers, 7271 (20%) former smokers, and 5303 (14%) current smokers. A total of 14,899 women (40%) were of normal weight, 13,836 (38%) were overweight, and 8104 (22%) were obese. During a maximum of 18 years and 487,013 person-years of follow-up, we detected

Discussion

In this study, current smoking increased the risk for incident diabetes mellitus in a large cohort of elderly women in a dose-dependent fashion. No statistically significant interaction existed between smoking and BMI on diabetes risk. All results were similar after adjusting for multiple demographic and lifestyle variables.

Our results are consistent with previous studies examining the risk of diabetes based on smoking status in women. Analysis of data on 434,637 women collected from 1959–1972

Conclusion

Our results clearly support other findings that smokers possess a higher risk for diabetes mellitus. We provide well-adjusted data with no observed statistically significant interaction between BMI and smoking on diabetes risk, implicating a BMI-independent mechanism for smoking-mediated diabetes risk.

Conflict of interest

No conflict of interest declared.

Acknowledgment

This work was supported in part by National Cancer Institute grant CA39742.

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