JOURNAL TRANSCRIPT
Research
Original Investigation
The Influence of Partner’s Behavior on Health Behavior Change The English Longitudinal Study of Ageing Sarah E. Jackson, PhD; Andrew Steptoe, DSc; Jane Wardle, PhD
IMPORTANCE Couples are highly concordant for unhealthy behaviors, and a change in one
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partner’s health behavior is often associated with a change in the other partner’s behavior. However, no studies have explicitly compared the influence of having a partner who takes up healthy behavior (eg, quits smoking) with one whose behavior is consistently healthy (eg, never smokes). OBJECTIVE To examine the influence of partner’s behavior on making positive health behavior changes. DESIGN, SETTING, AND PARTICIPANTS We used prospective data from married and cohabiting couples (n, 3722) participating in the English Longitudinal Study of Ageing, a large populationbased cohort of older adults (ⱖ50 years). Studying men and women who had unhealthy behaviors in 3 domains at baseline (ie, smoking, physically inactive, or overweight/obese), we used logistic regression analysis to examine the influence of the partner’s behavior in the same domain on the odds of positive health behavior change over time. MAIN OUTCOMES AND MEASURES Smoking cessation, increased physical activity, and 5%
weight loss or greater. RESULTS Across all domains, we found that when one partner changed to a healthier behavior (newly healthy), the other partner was more likely to make a positive health behavior change than if their partner remained unhealthy (smoking: men 48% vs 8%, adjusted odds ratio [OR], 11.82 [95% CI, 4.84-28.90]; women 50% vs 8%, OR, 11.23 [4.58-27.52]) (physical activity: men 67% vs 26%, OR, 5.28 [3.70-7.54]; women 66% vs 24%, OR, 5.36 [3.74-7.68]) (weight loss: men 26% vs 10%, OR, 3.05 [1.96-4.74]; women 36% vs 15%, OR, 3.08 [1.98-4.80]). For smoking and physical activity, having a consistently healthy partner also predicted positive change, but for each domain, the odds were significantly higher in individuals with a newly healthy partner than those with a consistently healthy partner (smoking: men OR, 3.08 [1.43-6.62]; women OR, 5.45 [2.44-12.16]) (physical activity: men OR, 1.92 [1.37-2.70]; women OR, 1.84 [1.33-2.53]) (weight loss: men OR, 2.28 [1.36-3.84]; women OR, 2.86 [1.55-5.26]). CONCLUSIONS AND RELEVANCE Men and women are more likely to make a positive health behavior change if their partner does too, and with a stronger effect than if the partner had been consistently healthy in that domain. Involving partners in behavior change interventions may therefore help improve outcomes.
JAMA Intern Med. 2015;175(3):385-392. doi:10.1001/jamainternmed.2014.7554 Published online January 19, 2015.
Author Affiliations: Health Behaviour Research Centre, Department of Epidemiology and Public Health, University College London, London, England (Jackson, Wardle); Psychobiology Group, Department of Epidemiology and Public Health, University College London, London, England (Steptoe). Corresponding Author: Jane Wardle, PhD, Health Behaviour Research Centre, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, England (
[email protected]).
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Research Original Investigation
Influence of Partner’s Behavior on Health Behavior
M
odifiable lifestyles and health-related behaviors are leading causes of morbidity and mortality worldwide.1-3 Smoking, poor diet, physical inactivity, and alcohol consumption have been identified as particularly important risk factors, accounting for over a third of all deaths in the United States in 2000. 2 Risk can be reduced by adopting healthier lifestyles, 4-11 b u t m a ny p e o p l e f i n d i t d i f f i c u l t t o m a ke l a s t i ng changes.12-14 A large body of evidence has shown that people tend to exhibit health behaviors similar to those around them, in particular their spouses. Concordance within couples has been documented for a wide range of health-related factors, including smoking,15-21 alcohol consumption,16-19,21-23 physical activity,19,21,24 body mass index (BMI),17,18,20,25,26 and dietary intake.18,27,28 Some of this concordance appears to be a result of assortative mating, with individuals selecting mates with behaviors similar to their own.17-20 There is also evidence that partners influence each other’s behavior. A number of studies have shown that spousal behavior status is a strong predictor of health behavior change; with people more likely to improve their behavior if their partner’s behavior is healthy, and more likely to adopt unhealthy behaviors if their partner’s behavior is unhealthy.15,22,25,29-39 For example, people are substantially more likely to begin smoking, and less likely to quit, if their partner smokes.31,32 Concordance for health behavior change has also been shown, with a change in one partner’s behavior predicting change in the other’s behavior.15,22,25,40-42 For example, weight loss intervention studies have found evidence of positive changes extending beyond treated individuals to spouses and other family members,43-45 indicating that one partner changing their behavior can encourage the other partner to change. However, the influence of a partner who changes to a healthy behavior compared with the influence of a consistently healthy partner is not known. Given that couples tend to report similar readiness to change health risk behaviors and express greater confidence in their ability to change if their partner is also ready to change,46 one might expect to see more successful behavior change in couples where both partners change together. This study aimed to investigate whether people are more likely to make a positive health behavior change in a given domain if their partner also changes from “unhealthy” to “healthy” in that domain than if their partner has been consistently healthy (eg, whether a smoker is more likely to quit if their partner quits smoking than if their partner was always a nonsmoker). Using prospective data from couples in a large cohort of English older adults, we classified individuals according to their partner’s health behavior (consistently healthy, consistently unhealthy, became healthy, or became unhealthy) over 2 time points and examined the influence of the partner’s behavior (or change) on the odds of our index case becoming healthy over the same interval. To test the effects robustly, we examined changes in 3 domains: smoking, physical activity, and body weight. 386
Methods Study Population Data are from couples in the English Longitudinal Study of Ageing (ELSA),47 a population-based study of middle-aged and older adults in the United Kingdom. The initial ELSA sample was drawn from households with 1 or more member 50 years or older responding to the Health Survey for England (HSE) in 1998, 1999, and 2001. All household members 50 years or older plus partners who were younger than 50 years or had joined the household since the HSE were invited for interview. From 2002, ELSA participants have been followed up in biennial waves with a computer-assisted interview and selfadministered questionnaires. Refreshment samples were recruited at waves 3, 4, and 6. In addition to the data collected at each wave, health examinations were conducted on alternate waves, with nurses visiting the home to collect objective measures of anthropometry. ELSA has received approval from various ethics committees, including the London MultiCentre Research Ethics Committee, and full informed written consent has been obtained from all participants.
Definition of Baseline and Follow-up Time Points Smoking and physical activity status have been assessed in each wave of ELSA to date (waves 1-6), and heights and weights have been measured in even waves (waves 2, 4, and 6). We therefore assessed smoking cessation and increase in physical activity over a 2-year interval and weight loss over a 4-year interval. For each health domain, we used the first 2 consecutive waves for which both partners had data available, with the first wave constituting the baseline data and the second wave constituting the follow-up data.
Measures Health Behaviors Smoking status was assessed with the question “Do you smoke cigarettes at all nowadays? (yes/no).” Among those answering yes at baseline, the mean (SD) number of cigarettes smoked daily was 15.35 (9.50) in men and 14.26 (7.63) in women. Smoking cessation was defined as answering yes at baseline and no at follow-up. Physical activity was assessed with a question adapted from the Whitehall II study48: “Do you take part in any sports or activities that are (vigorous/moderately energetic/mildly energetic)?” Response options were “more than once a week,” “once a week,” “one to three times a month,” and “hardly ever or never.” We classified participants as active (moderate or vigorous activity at least once a week) vs inactive (less than this). An increase in physical activity was defined as being inactive at baseline and active at follow-up. Weight was measured to the nearest 0.1 kg using THD305 portable electronic scales (Tanita Corporation). Height was measured to the nearest millimeter using a portable stadiometer. At each assessment, the nurses who took the measurements recorded any factors that could compromise measurement reliability (eg, participant was stooped or unwilling to remove shoes). We excluded measurements
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Influence of Partner’s Behavior on Health Behavior
judged by the nurse to be unreliable. Body mass index (calculated as weight in kilograms divided by height in meters squared) was used to classify participants’ weight status as normal (BMI