Tuesday October 29 2013
Gardening was just one of the activities studied
“Gardening 'linked to longer lives','' is the claim on the BBC News website. A Swedish study has found that older adults who took part in physical activity on a frequent basis had improved health outcomes compared to their more sedentary counterparts.
The study involved 60 year old men and women and looked at the impact of what the researchers termed “non-exercise physical activity” (NEPA).
NEPA equates to everyday tasks involving some level of physical activity, such as performing home repairs, gardening, fixing the car, and as this was a Swedish study, hunting, fishing and gathering mushrooms and berries (the latter apparently being a favourite pastime in Sweden).
The study found that people who reported regular NEPA had a better outcome that those who didn’t.
Specifically, those participants with high levels of NEPA were associated with a 27% reduced risk of heart attack, stroke or angina, and a 30% reduced risk of death during 12.5 years of follow-up.
An inherent limitation of the study design is that it cannot prove levels of NEPA are directly responsible for the reduction in risk of cardiovascular events or death. Any reduction in risk is likely to be due to a combination of various health and lifestyle factors.
However, this study adds to the current evidence suggesting that any physical activity, regardless of whether it is perceived as exercise or not, is good for our health, unlike remaining sedentary.
Where did the story come from?
The study was carried out by researchers from Karolinska University Hospital and The Swedish School of Sport and Health Sciences, Sweden. It was funded by The Swedish Order of Freemason-Grand Swedish Lodge, Stockholm County Council, the Swedish Heart and Lung Foundation, the Swedish Research Council and the Tornspiran Foundation.
The study was published in the peer-reviewed British Journal of Sports Medicine.
The quality of the reporting of this study was not as good as it could have been. Both the Daily Express and the Mail Online fell into the trap that these results ‘proved’ that daily activities were “just as good as going to the gym”.
However, the research compared health outcomes for people who performed high levels of non-exercise physical activity with people who performed low levels of non-physical activity, rather than comparing non-exercise physical activity with going to the gym. In addition, to ‘prove’ that one activity was as good as another, the researchers would have had to perform a randomised controlled trial.
Also, only earlier this month, a study was published that strongly suggested non-exercise physical activities (NEPA), while certainly beneficial, are not an effective substitute for moderate-intensity aerobic activities.
There was also a strange obsession about gardening in most of the headlines. The research tried to look at general ‘non-exercise physical activity’ and looked at five different-types of activity: performing home repairs; cutting the lawn/hedge; car maintenance; taking bicycle rides, skiing, ice-skating, going hunting or fishing; and gathering mushrooms or berries.
What kind of research was this?
This was a cohort study that carried out two forms of analysis. The researchers aimed to look at the association between levels of non-exercise physical activity (NEPA) in men and women aged 60 and cardiovascular health at the start of the study (a cross-sectional analysis) and the association between NEPA and cardiovascular disease and death over 12.5 years of follow-up (the prospective cohort study).
These study designs cannot prove causation, as the relationship between general activity and cardiovascular health and mortality is likely to be influenced by a number of other health and lifestyle factors.
However, the most effective method of proving causation – a randomised controlled trial (RCT) would be both impractical and unethical as it would require you to ‘force’ people to adopt certain patterns of behaviour for many years.
What did the research involve?
The researchers invited every third 60 year old man and woman in Stockholm County to a health screening study. People with a history of cardiovascular disease events (heart attacks, heart failure, or stoke), rather than just having risk factors, were excluded – 1,816 men and 2,023 women were included in the study.
Participants filled in a questionnaire about non-exercise physical activity and exercise habits at the start of the study.
The questionnaire asked about the frequency over the past 12 months of five activities that promote non-exercise physical activity:
- performing home repairs
- cutting the lawn/hedge
- car maintenance
- taking bicycle rides, skiing, ice-skating, going hunting or fishing
- gathering mushrooms or berries
Participants were divided into thirds according to their responses: those that performed low levels of NEPA, those that performed moderate amounts, and those that performed high amounts.
The participants were also asked to report their physical activity during leisure time:
- sedentary (light activity for less than two hours per week)
- light-intensity physical activity (at least two hours per week)
- regular moderate-intensity physical activity (at least 30 minutes, one or two times per week)
- regular high-intensity physical activity (at least 30 minutes, at least three times per week)
Cardiovascular health was assessed through physical examinations and laboratory tests, which principally aimed at measuring risk factors for metabolic syndrome – a medical term for a group of factors, such as obesity and high blood pressure, that can increase the risk of certain conditions such as heart disease and stroke.
This included measurement of:
- waist circumference
- blood pressure
- levels of high-density (‘good’) cholesterol, low-density (‘bad’) cholesterol, total cholesterol, triglycerides (another blood fat), insulin and glucose
They also looked at a measure of blood clotting (fibrinogen).
The participants were followed-up for 12.5 years for cardiovascular events (heart attack, angina or stroke) and mortality (death).
The researchers looked at the association between baseline levels of NEPA and baseline cardiovascular health; and then the association between NEPA and cardiovascular events and mortality during follow-up.
The researchers adjusted their analyses for the following factors that may also have influenced the results (confounders):
- leisure time activity
- marital status
- education level
- current smoking status
- alcohol intake
- dietary intake of vegetables
- living conditions
- financial status
- family history of high blood pressure, high cholesterol, diabetes or cardiovascular disease
What were the basic results?
At the start of the study, high non-exercise physical activity was associated with a lower waist circumference and better levels of high-density lipoprotein cholesterol and triglycerides (fats) in both men and women, and with lower insulin, glucose and fibrinogen levels in men (compared to low levels of non-exercise physical activity).
People who performed moderate or high levels of NEPA but no regular exercise had lower odds of metabolic syndrome than people who performed low levels of NEPA and no regular exercise. People who performed both high-levels of NEPA and regular exercise had the lowest odds of metabolic syndrome.
During the follow-up period, 476 people experienced a fatal or non-fatal cardiovascular event and 383 people died.
High NEPA was associated with a 27% lower risk of a cardiovascular event during follow-up compared to low non-exercise physical activity (hazard ratio [HR] 0.73, 95% confidence interval [CI] 0.57 to 0.94).
High NEPA was associated with a 30% lower risk of death during follow-up compared to low NEPA (HR 0.70, 95% CI 0.53 to 0.93).
How did the researchers interpret the results?
The researchers concluded that “a generally active daily life was, regardless of exercising regularly or not, associated with cardiovascular health and longevity in older adults.”
This study found that in a population-based sample of older adults (aged 60), high levels of non-exercise physical activity, or ‘an active daily life’ was associated with better levels of cardiovascular risk factors.
When followed over time, it was found an active daily life was associated with approximately 30% reduced risk of both a cardiovascular event (stroke, angina, heart attack) and death from any cause.
These associations were seen after adjusting for regular exercise, and for a number of other factors that could explain the association seen (confounders).
This study was a cross-sectional and cohort study. This means that it cannot show that high levels of non-exercise physical activity caused the reduction in risk of cardiovascular events or death.
The researchers attempted to adjust for various confounders. Though it is still likely that the reduced cardiovascular risk observed with increased activity is not due to activity alone, but is being influenced by a variety of other health and lifestyle factors.
There are other limitations. In this study, non-exercise physical activity and exercise were both self-reported. It is also unclear how applicable these results will be to people of other age groups, or to people of other cultures. For example, for people living in towns and cities, the opportunity to pick mushrooms and berries is a tad limited.
Finally, this study should not be taken as proof that daily activities such as gardening are as beneficial as more strenuous exercise such as jogging. Rather it should be assessed as adding to the current evidence suggesting that any physical activity, regardless of whether it is perceived as exercise or not, is good for our health.
As a certain supermarket chain puts it – “Every little helps”.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.