"Healthy habits extend disease-free life 'by up to a decade'," reports The Guardian.

More people are living longer, thanks to the rise in life expectancy. The downside is that more people are living with diseases like diabetes, cancer and heart disease.

Yet many of these diseases are linked to lifestyle-related risk factors like poor diet, being overweight and smoking.

A study of more than 110,000 people assessed 5 healthy habits, and estimated how much longer people with these habits live, and also how many of those extra years are likely to be disease-free.

The study found that women who adopted 4 or 5 of the habits were likely to live an extra 10 years without cardiovascular disease (heart disease and stroke), cancer or type 2 diabetes compared with women adopting none. The corresponding figure for men was 7 years.

The markers of a healthy lifestyle used by the researchers were:

not smoking

having a healthy body mass index (BMI) of 18.5 to 24.9

doing 30 minutes moderate to vigorous exercise a day

drinking alcohol only in moderation (defined in this study as just under 2 units for women and 4 units for men daily)

having a healthy diet score in the top 40% of people in the study

While the way the study was run cannot prove the healthy lifestyle directly caused the additional years of healthy life, it adds considerable weight to existing evidence that has already shown these lifestyle habits reduce the chance of disease. Find out more about leading a healthy lifestyle.

Where did the story come from?

The researchers who carried out the study were from the Harvard TH Chan School of Public Health and Harvard Medical School in the US, Erasmus Medical Centre in the Netherlands and Huazhong University of Science and Technology in China.

The study was funded by the US National Institutes of Health. It was published in the peer-reviewed British Medical Journal on an open access basis, so is free to read online.

The study was widely reported in the UK media. The reports in The Times and the Mail Online implied that having healthy habits at age 50 would lead to a longer life – but the study followed participants for many years, assessing habits every 2 years for 28 to 34 years. Long-term healthy habits, not habits at any particular age, are what counts.

What kind of research was this?

The researchers used 2 cohort studies.

Cohort studies are good ways to look at links between risk factors (such as unhealthy lifestyle habits like smoking and not exercising) and outcomes (such as getting cardiovascular disease, cancer, diabetes or dying).

However, cohort studies cannot prove that the risk factors directly cause the outcomes. Other factors may be involved.

What did the research involve?

Researchers used information from 2 cohorts of men and women that were studied in the US between 1980 and 2014, the Nurses' Health Study of female nurses, and the Health Professionals Follow-up Study of male doctors, dentists and other healthcare professionals.

The women were followed up for 34 years and the men for 28 years.

During the studies, the participants completed questionnaires every 2 years that included information about their weight and height, smoking status, physical activities, alcohol intake and diet.

They were also asked whether they had been diagnosed with type 2 diabetes, cardiovascular disease or cancer (the researchers reviewed medical records to confirm diagnoses). Deaths were reported via a registry.

The researchers calculated how long people lived before being diagnosed with one of the conditions studied, according to how many healthy lifestyle factors they adopted. People were assigned a healthy lifestyle score of 0 to 5, with 5 indicating they had all 5 healthy lifestyle factors and 0 that they had none.

The researchers then used the information to construct models to estimate how long someone aged 50 could expect to live free of cardiovascular disease, diabetes or cancer, according to their healthy lifestyle score.

They also looked at which unhealthy lifestyles had most effect on the outcome, and on which diseases were most affected by lifestyle.

What were the basic results?

Overall, women and men aged 50 could expect to live another 30 to 40 years, and 75% to 84% of that time would be free of the diseases studied.

However, women and men with healthy lifestyles could expect to live longer, healthier lives. They were less likely to be diagnosed with cancer, cardiovascular disease or diabetes, and if they did get these diseases, they survived for longer after diagnosis.

The study estimates that for people aged 50:

women with 4 or 5 healthy lifestyle habits can expect to live another 41.1 years, 34.4 years of which would be free of disease

women with no healthy lifestyle habits can expect to live another 31.7 years, 23.7 of which would be free of disease

men with 4 or 5 healthy lifestyle habits can expect to live another 39.4 years, 31.2 of which would be free of disease

men with no healthy lifestyle habits can expect to live another 31.3 years, 23.5 of which would be free of disease

The people with the worst disease-free life expectancy were men who smoked heavily and men and women who were obese (body mass index over 30).

Diabetes was the condition most closely linked to lifestyle, with 90% of people diagnosed with diabetes in the study estimated to have the condition because of unhealthy lifestyles.

Cancer was the least closely linked, with 50% of cancers estimated to be due to unhealthy lifestyles.

How did the researchers interpret the results?

The researchers said: "We observed that a healthier lifestyle was associated with a lower risk of cancer, cardiovascular disease and diabetes, as well as mortality, with an increased total life expectancy and number of years lived free of these diseases."

Conclusion

It is no surprise that adopting a healthy lifestyle is likely to lead to a longer life and less chance of getting diabetes, cancer or cardiovascular disease.

The study adds to the existing evidence that shows not smoking, being a healthy weight, exercising, eating well and drinking only in moderation is likely to increase our chances of living disease-free for longer.

Cohort studies cannot prove that lifestyle factors directly cause outcomes like length of life or disease, however. Other factors – such as genetics, other health conditions and socioeconomic circumstances – may also be involved. But there is already good evidence to show that the healthy lifestyle factors measured are linked to better health, even if they cannot completely eliminate disease risk.

There are other limitations to the study.

Most of the lifestyle data was self-reported, which could lead to some inaccuracy in measurement.

Diseases were self-reported, though these were medically confirmed so more likely to be reliable.

Also, the study participants were all educated healthcare professionals, so might be expected to have a healthier-than-average lifestyle. They were also mostly white and all lived in the US. We do not know if the results would apply to other groups of people.

Overall, this is good news for people who try to adopt a healthy lifestyle.

There are many reasons why some people find this harder than others. The results should encourage governments and public health authorities to try and make it easier for everyone to live healthy lives.

Find tips, tools and advice about how to make good choices about health and wellbeing.

Analysis by Bazian

Edited by NHS Website