Living with a Smoker and General and Central Adiposity in Middle-Aged and Older Women

Abstract

Purpose:

We hypothesized that living with a smoker would be positively associated with general and central adiposity among middle-aged and older women.

Design:

Prospective across up to 8 years.

Setting:

Women’s Health Initiative Observational Study.

Sample:

83,492 women (age 50 to 79 at baseline).

Measures:

The predictor was living with a smoker at baseline. Outcomes were clinic-assessed obesity and high waist circumference, examined cross-sectionally at baseline and prospectively at Year 3 and (for self-reported obesity) Year 8.

Analysis:

All analyses used logistic regression and controlled for sociodemographic factors and participants’ current smoking; prospective analyses also adjusted for baseline obesity or high waist circumference.

Results:

Living with a smoker was associated: (a) cross-sectionally with obesity (n = 82,692, OR = 1.38, p < .001) and a high waist circumference (n = 83,241, OR = 1.41, p < .001) and (b) prospectively with obesity (n = 68,753, OR = 1.22, p < .001) and a high waist circumference (n = 68,947, OR = 1.22, p < .001) three years later and obesity (n = 38,212, OR = 1.21, p < .001) eight years later.

Conclusion:

These results document an essentially unrecognized health risk associated with living with a smoker. For practitioners, these findings underscore the need for innovative household-level interventions for families living with a smoker integrating established smoking- and obesity-prevention efforts.

Purpose

Substantial evidence supports a direct link between second-hand smoke (SHS) exposure and increased morbidity.¹ A small number of studies have found that SHS exposure is also associated with a higher body mass index (BMI).^2,3 However, the available evidence is cross-sectional, leaving open the possibility that confounding factors may explain the passive smoking–BMI relationship. Moreover, previous research has not examined the link between passive smoking and obesity or high waist circumference. At age 60, weight-related cardiometabolic diseases predict a significant reduction in women’s longevity,⁴ and intentional weight loss is associated with a significant decrease in mortality risk among older adults.⁵ We hypothesized that living with a smoker would be positively associated with general and central adiposity among middle-aged and older women.

Methods

Design

The present study uses the WHI Observational Study, which examines the relationship between health risk factors and disease among 93,676 women who were between 50 and 79 years of age at enrollment. Women were enrolled at 40 centers throughout the U.S. located primarily at academic health centers in 24 states and the District of Columbia.⁶ Health behavior data were collected at baseline, a 3-year follow-up, and additional follow-ups through 8 years with an average follow-up response rate of over 94% among participants due for contact. Participants provided written informed consent. The present study was approved by the University of Texas at Austin Institutional Review Board (Approval Number 2009-03-0079).

Sample

The present study included 83,492 participants who provided data on all predictive variables and at least one outcome at baseline. At baseline, the present sample was an average age of 63.5 (SD = 7.36) years. The ethnic/racial composition was 84% White-not of Hispanic origin, 8% Black/African American, 4% Hispanic/Latino, and 4% other groups. Median income level was $35,000 to < $50,000; 43% of participants had completed college and 62% were married.

Measures

Living with a smoker at baseline was indexed by responding “yes” to both of two items: “Since age 18, have you ever lived with someone who smoked cigarettes inside your home?”, and, if yes, “Does anyone living with you now smoke cigarettes inside your home?”.

Participant current smoking at baseline was indexed by responding “yes” to both of two items: “During your entire life, have you smoked at least 100 cigarettes?”, and, if yes, “Do you smoke cigarettes now?”.

BMI (weight (kg) / height (m)2) and waist circumference were assessed by certified clinic staff at baseline and Year 3. We used binary cut-offs based on previous findings relating BMI and waist circumference to mortality among women in the WHI.⁷ General adiposity was indexed as a BMI in the obese range (BMI ≥ 30). Central adiposity was indexed as a waist circumference in the high-risk range (waist circumference ≥ 90 cm). At baseline, 20,862 (25%) participants were obese and 25,913 (31.1%) participants had a high waist circumference.

In addition to the clinic-assessed measures, participants reported their weight at the last Observational Study assessment, Year 8. This information and clinic-assessed height at Year 3 allowed us to compute a self-report measure of obesity at Year 8.

Analysis

The predictor was living with a smoker at baseline. Outcomes were clinic-assessed obesity and high waist circumference, examined cross-sectionally at baseline and prospectively at Year 3 and (for self-reported obesity) Year 8. All analyses used logistic regression and controlled for age, educational level, ethnic/racial group, income level, marital status, and participants’ current smoking. To investigate change, prospective analyses also adjusted for baseline clinic-assessed obesity or high waist circumference in respective analyses.

Results

Baseline.

In logistic regression analyses at baseline, we examined the cross-sectional association of living with a smoker with clinic-assessed obesity and high waist circumference. Controlling for all covariates, living with a smoker at baseline was associated with 38% increased odds of being obese and 41% increased odds of having a high waist circumference at baseline (see Table 1).

Table 1.

Results of logistic regression analyses with living with a smoker at baseline predicting adiposity cross-sectionally at baseline and prospectively at the 3-year follow-up.

	Obesity			High Waist Circumference
	n	ORa	95% CIb	n	OR	95% CI
Baseline	82,692	1. 38*	(1.30, 1.46)	83,241	1. 41*	(1.33, 1.49)
Year 3	68,753	1.22*	(1.09, 1.36)	68,947	1.22*	(1.11, 1.34)

^aOdds Ratio

^bConfidence Interval

^*p < .001

Three years.

In logistic regression analyses, we examined the prospective association of living with a smoker at baseline with clinic-assessed obesity and high waist circumference at Year 3. Controlling for all covariates, as well as adjusting for baseline obesity or high waist circumference in respective analyses, living with a smoker at baseline was associated prospectively with 22% increased odds of being obese three years later and 22% increased odds of having a high waist circumference three years later (see Table 1).

Eight years.

In a logistic regression analysis, we examined the prospective association of living with a smoker at baseline with the self-report measure of obesity at the last Observational Study assessment, Year 8. Controlling for all covariates, as well as adjusting for clinic-assessed baseline obesity, living with a smoker at baseline was associated prospectively with 21% increased odds of being obese eight years later (n = 38,212, OR = 1.21, p < .001, 95% CI = 1.05, 1.39).

Discussion

Summary

These results support previous studies that have found that SHS exposure is cross-sectionally associated with a higher body mass index.^2,3 In addition, the present study strengthens inference that passive smoking is associated with body weight by demonstrating that the predictive link is evident prospectively across three-year and eight-year intervals. The present findings further extend previous research by demonstrating that living with a smoker is linked to obesity and high waist circumference, which are associated with increased mortality among women in the WHI.⁷ Mechanisms are likely complex, and may involve household culture, including unhealthy diet⁸ and physical inactivity⁹.

Limitations

A limitation of the WHI Observational Study is a self-report measure of living with a smoker. In addition, findings are specific to middle-aged and older women. Future research examining this question should be broadened to other groups. Cross-sectional findings suggest that the positive association between SHS exposure and BMI pertains to men as well as women.^2,3

Significance

These results document an essentially unrecognized health risk associated with living with a smoker. For practitioners, these findings underscore the need for innovative household-level interventions for families living with a smoker integrating established smoking- and obesity-prevention efforts. Focusing first on tobacco using a self-report measure of household smoking would address the smoker’s health behavior, as well as enlist the smoker’s support. Escoffery and colleagues¹⁰ describe a home smoking ban requiring minimal expertise or burden to implement. Gorin and colleagues¹¹ describe a multi-level home environment intervention for adults that simultaneously addresses food, exercise, sedentary behavior, and partner support.

SO WHAT?

What is already known on this topic?

A small number of studies have found that living with a smoker is associated cross-sectionally with a higher BMI.

What does this article add?

We show that the predictive link between SHS and body weight is evident prospectively across three-year and eight-year intervals and extends to general and central adiposity.

What are the implications for health promotion practice or research?

These findings underscore the need for innovative household-level interventions for families living with a smoker integrating established efforts on home smoking bans with multi-level home environment interventions addressing food, exercise, sedentary behavior, and partner support.