“Fitness 'rubs off on your partner’,'' BBC News reports.
This headline is based on a study of more than 3,000 married couples aged 50 and over in the UK, where at least one of the partners smoked, was inactive, or was overweight or obese at the start of the study. It followed them up and looked at their and their partner’s behaviours over time.
It found that a person was more likely to change their unhealthy behaviours if their partner did too, more so than if they had a partner who was always healthy, or one who remained unhealthy.
There are some limitations to the study. For example, while the researchers took into account some factors that could affect the results, others – such as unmeasured health conditions – could still be having an impact.
Still, the findings seem plausible; working together as a team to improve health, whether it be just you or your partner, or in a larger exercise or weight loss group, may help in practical ways (such as eating the same foods), as well as boosting motivation and confidence levels.
The study was carried out by researchers from University College London. Funding was provided by the US National Institute on Aging and a consortium of UK government departments co-ordinated by the Office for National Statistics. Additional support for the authors was provided by the British Heart Foundation and Cancer Research UK.
The study was published in the peer-reviewed medical journal JAMA Internal Medicine.
The coverage of this study in the news has been generally reasonable. The BBC’s headline “Fitness ‘rubs off on your partner’” may make it sound like you don’t have to do anything to get fitter – as long as your partner is – but unfortunately this is not the case.
This was an analysis of data from an ongoing cohort study of older adults called the English Longitudinal Study of Ageing (ELSA). It aimed to look at the effect of a partner’s behaviour on a person making healthy behaviour changes.
If a person has unhealthy behaviours (such as eating unhealthily), their partner is also likely to, and if one of them changes this behaviour then the other often does too.
In this study the researchers specifically wanted to look at whether there was a difference in the effect of having a partner who is consistently healthy (e.g. had always eaten healthily) and one who had unhealthy behaviour but then makes a positive change (e.g. starts eating healthily).
While other studies have assessed the impact of partners changing behaviour, few have assessed this specific question.
This type of study is the best way of looking at the impact of behaviour that people choose themselves in real life. The main limitation to this type of study is that factors other than the one the researchers are looking at (called confounders) could also have an effect. The researchers can take steps in their analyses to reduce the effect of potential confounders, but they can never be entirely sure they have accounted for every confounder.
The ELSA study started prospectively collecting data on adults aged 50 and over in England in 1998.
For the current study researchers looked at information on 3,722 married couples who lived together, where at least one had an unhealthy behaviour or characteristic at the start of the study (smoking, physically inactive, or overweight or obese). They then looked at whether their partner’s behaviour over time had an influence on whether the person changed their unhealthy behaviours.
Participants in ELSA had taken part in the Health Survey for England in 1998, 1999 and 2001. All household members aged 50 and over, as well as partners were invited for interview. Those who enrolled were sent a computer-assisted interview and self-administered questionnaires every two years from 2002. Smoking and physical activity were assessed in every questionnaire. Every four years this assessment included a health assessment, where a nurse visited the participants in their homes. This assessment included measuring height and weight.
For the current study, the researchers analysed data for the first two consecutive assessments that the person and their partner completed. They looked at smoking, physical activity and weight in people and their partners, and whether individuals:
A partner was considered “consistently” healthy if they did not have the unhealthy behaviour at either the first or the second assessment.
Couples where the partner moved from a healthy behaviour to a less healthy behaviour were excluded from the analyses, as there were so few of them.
The researchers took into account a number of potential confounders in their analyses, including:
At the start of the study:
By the next assessment overall:
The researchers found that when one partner changed to a healthier behaviour, the other person was more likely to also change to a healthier behaviour than if their partner had remained unhealthy. This was the case across all three behaviours:
Having a consistently healthy partner also increased the likelihood that a person would stop smoking or become more active, but not the likelihood of losing weight. For all three behaviours, having a partner who changed to a healthier behaviour was associated with a greater likelihood of a person themselves changing behaviour than having a partner with consistently healthy behaviour. The impact of a partner’s behaviour was limited to that specific behaviour (e.g. smoking, or activity, or weight loss) and was not associated with changes in other behaviours in the other partner.
The researchers conclude that “men and women are more likely to make a positive health behavior (sic) change if their partner does too, and with a stronger effect than if the partner had been consistently healthy in that domain”. They suggest that involving partners in programmes aiming to get a person to change their behaviour might improve the outcomes of these programmes.
This cohort study has found that individuals with unhealthy behaviours such as smoking, being inactive or being overweight are most likely to change these behaviours if their unhealthy partner also changes these behaviours.
Having a partner who has consistently healthy behaviours was also associated with a greater likelihood of change in smoking and activity compared to a consistently unhealthy partner, but less so than having a partner who changed behaviour.
There were some limitations to the study, including that:
It is known that social support from family, friends or other groups can be an important component in people changing their behaviours.
This study supports this concept, and suggests that the impact may be greatest, for partners at least, if that partner is also changing their behaviour.
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