"People who stick to five healthy habits in adulthood can add more than a decade to their lives," reports The Guardian. Regular readers of Behind the Headlines, or health news in general, will be unsurprised to learn that the habits are:
- not smoking
- maintaining a healthy weight
- doing at least 30 minutes of moderate exercise a day
- eating a healthy diet high in fruit, vegetables and whole grains, and low in red meat, saturated fats and sugar
- not drinking too much alcohol – current UK guidance recommends no more than 14 units a week for men and women
The findings are based on a US study that looked at the habits and health of about 123,000 health professionals over 30 years. Participants who adopted all 5 were 74% less likely to die during the study than those who adopted none of them. Women with these healthy habits lived 14 years longer on average than their counterparts, and men about 12 years longer.
These results support current understanding of the benefits of healthy lifestyle habits.
If you've been leading an unhealthy lifestyle, it may be unrealistic to attempt to switch to better habits overnight. One option is to focus on adopting just 1 habit first and that may lead to you adopting more, or perhaps even all, of them. For example, if you quit smoking, you may find you have more stamina to exercise.
Encouragingly, the study did find that each healthy habit individually contributed to reducing the risk of premature death.
Where did the story come from?
The study was carried out by researchers from the Harvard T.H. Chan School of Public Health in Boston, US, and other centres in China, the UK, the Netherlands and the US. It was published in the peer-reviewed medical journal Circulation.
The UK and international media covered the study accurately.
What kind of research was this?
This was a prospective cohort study of adults in the US that looked at how lifestyle habits affected how long participants lived and what diseases they died from.
This type of study is the best way of investigating this question, as it would not be realistic or ethical to set up a randomised controlled trial where people would be assigned to adopt either healthy or unhealthy habits for a long period of time.
The main limitation of a prospective cohort approach is that it makes it difficult to pinpoint the effect of individual habits on lifespan. To address this, the researchers took appropriate steps to account for the influence of important non-lifestyle-related factors, such as family history of serious conditions.
What did the research involve?
The researchers analysed information from around 123,000 adults, aged 30 to 75 years at the start of the study, who were followed up for about 30 years. The researchers looked at whether those with healthy habits lived longer than those with unhealthy habits and, if so, by how much.
The data came from the Nurses' Health Study (which included only women) and the Health Professionals Follow-up Study (which included only men). Both started in the 1980s and ran until 2014. They used validated questionnaires to assess participants' eating and drinking habits every 4 years and physical activity every 2 years. Participants were also asked whether they smoked and how much they weighed every 2 years.
Diet was assessed using the Alternate Healthy Eating Index (AHEI). This system gives participants a score based on how well their diet meets recommended serving amounts of foods, including:
- high intake of vegetables, fruit, nuts, whole grains, polyunsaturated fatty acids and long-chain omega-3 fatty acids
- low intake of red and processed meats, sugar-sweetened beverages, trans fats and salt
Participants whose AHEI scores were in the top 40% were considered to have a healthy diet.
The researchers looked at 5 healthy behaviours or characteristics:
- having a healthy diet
- never smoking
- being physically active – at least 30 minutes of moderate or vigorous activity a day
- drinking a moderate amount of alcohol – between approximately 0.5 and 2 units a day for women, and 0.5 and 3 units a day for men
- not being overweight or obese – so having a body mass index (BMI) of 18.5 to 24.9
Participants were given a score of 1 for each trait they had and 0 for each they did not. So a person with all 5 healthy traits would score 5 and a person with none would score 0.
The researchers also used information collected during 2013-14 as part of a national survey (the annual US National Health and Nutrition Examination Survey) to assess how common these habits and characteristics were in the US population.
Death and cause of death were identified using national records and family reports. The researchers also looked at causes of death in the US using the US Centers for Disease Control and Prevention WONDER national database.
They then analysed how participants' healthy behaviours over time affected lifespan and risk of death from cancer or cardiovascular disease, taking into account factors including:
- age at the start of the study
- menopausal status
- whether they took multivitamins, regular aspirin or hormone replacement therapy
- family history of diabetes, heart attack or cancer
- whether they had diabetes, high blood pressure or high cholesterol themselves
The researchers also estimated how many of the deaths in the study would have been prevented if all participants adopted the 5 healthy habits, and used statistical methods to estimate life expectancy of participants with differing levels of healthy habits.
What were the basic results?
Very few people in the study exhibited all 5 healthy habits – only 1.3% of women and 1.7% of men. During the study, 42,167 participants died, including 13,953 from cancer and 10,689 from cardiovascular disease.
Each of the 5 healthy lifestyle factors was associated with a reduced risk of dying during the study and of dying from cancer or cardiovascular disease specifically.
It also reduced the risk of dying from cancer during the study by 65% (HR 0.35, 95% CI 0.27 to 0.45) and of dying from cardiovascular disease during the study by 82% (HR 0.18, 95% CI 0.12 to 0.26).
The researchers calculated that if all participants had all 5 healthy lifestyle habits, this could have:
- reduced deaths during the study by about 61%
- reduced deaths from cancer during the study by about 52%
- reduced deaths from cardiovascular disease during the study by about 72%
They also estimated that if people in the general US population adopted these 5 healthy lifestyle habits, their average life expectancy at age 50 years compared with people who adopted none of them would be:
- 14 years longer for women (95% CI 11.8 to 16.2)
- 12.2 years longer for men (95% CI, 10.1 to 14.2)
How did the researchers interpret the results?
They said: "Adopting a healthy lifestyle could substantially reduce premature [death] and prolong life expectancy in US adults."
This large US study estimated the potential positive influence on life expectancy for adults adopting the 5 key healthy habits of:
- having a healthy diet
- never smoking
- being physically active
- drinking a moderate amount of alcohol
- not being overweight or obese
The study had a number of strengths, including its large sample size, long follow-up period, and assessment of habits and BMI at multiple time points.
However, as with all studies of this type, there were some limitations.
While the researchers did their best to account for the effect things such as age and ethnicity may have had, the results could still have been affected by other factors, such as pre-existing medical conditions and socioeconomic status.
The study also relied on participants reporting their own habits, and self-reporting isn't always accurate.
Furthermore, as the study only included health professionals, most of whom were white, the results may not be representative for a more mixed sample of participants.
Finally, the proportion of deaths that could be prevented by adopting the healthy habits very much depends on the population's existing habits. Therefore, these figures may not be applicable to populations from different countries and cultures, or even to a different time period.
However, regardless of the limitations, the estimates provided by this study should hopefully encourage more people to adopt a healthy lifestyle. For a wide range of advice on a healthier lifestyle, visit the NHS Live Well hub.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Guardian, 30 April 2018
The Sun, 30 April 2018
Mail Online, 30 April 2018
Links to the science
Circulation. Published online April 30 2018