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Impact of healthy lifestyle factors on life expectancy

Chronic cardiovascular and metabolic diseases are today spreading around the globe and they are among the leading causes of mortality in the world. In most of cases, the patients could see their health improve and some diseases could even be avoided if certain conditions in the lifestyle were met. Regular physical activity and healthy eating are among the essential conditions to limit the appearance of certain health problems and certain diseases. The consumption of alcohol and tobacco are also important risk factors. An epidemiological meta-analysis has shown that about 60% of premature deaths are attributable to poor health choices such as smoking, excessive drinking, sedentary lifestyle, poor diet and obesity.

We in the West are the first generation in human history in which the mass of the population has to deliberately exercise to be healthy.
– Prof. J.N. Morris

Although one of the wealthiest developed countries in the world, the life expectancy of Americans is the 31st in the world at birth in 2015, with a total health expenditure per capita equivalent to 17.1% of gross domestic product. Cardiovascular diseases and cancers are the main diseases, but also the most expensive. They are, however, largely preventable. But what is the true impact of healthy lifestyle on life expectancy ?

The Study

To answer this question, an international team of researchers has statistically analyzed data from different epidemiological studies conducted over a period of several years in American men and women to quantify the association between some lifestyle-related factors and mortality. Using other statistical data on the American population, researchers were able to estimate the impact of these factors on life expectancy.

For this, the researchers used data from the Nurses' Health Study (NHS), an epidemiological study of American nurses aged 30 to 50 years, from 1980 to 2014, which included information related to health, life and food. To obtain information about a male public, the researchers used Harvard and the National Cancer Institute's Health Professionals Follow-Up Study (HPFS) on the health status of health professionals (40 to 75 years) from 1986 to 2014. The data from this study were the same as for the NHS study, the objective was to see the impact of lifestyle and eating behaviors on diseases and mortality. In total, researchers used data from 78,865 women and 44,354 men.

The researchers identified 5 low-risk lifestyle factors : healthy diet, physical activity, smoking, alcohol consumption, and body mass index (BMI). These factors are described below :

• The diet quality was evaluated via a scoring system validated scientifically and strongly associated with the onset of cardiometabolic diseases in the general population. A healthy diet was defined by a score in the top 40%. The scoring system included 10 criteria, each receiving a score of 0 to 10, with 10 being the best score : High intakes of vegetables, fruits, nuts, whole grains, polyunsaturated fatty acids, long-chain Omega-3 fatty acid and low intakes of red meats, sugar sweetened beverages, trans fats and sodium.
• For physical activity, it was necessary to realize at least 30 minutes a day of moderate or vigorous activity which require an energy expenditure of at least 3 METs-hour (ie, 180 METs-minutes, or 60 min at 3 METs or 30 at 6 METs).
• For smoking, the low risk was to never smoke.
• For alcohol, the low risk was moderate consumption, ie between 5 and 15 g / day for women and 5-30 g / day for men.
• For the body mass index (BMI), the low risk was defined as a BMI between 18.5 and 24.9 kg / m².

For each low-risk factor, the participant received 1 point if he met the requirements for each factor. If this was not the case, no points were awarded. So a score of 5 indicated the "healthiest" lifestyle, and 0, the "worst".

The researchers then used data from a study conducted between 2013 and 2014 (NHANES) to estimate the distribution of lifestyle factors among the US population. And finally, using mortality statistics in the United States, they estimated life expectancy based on low-risk lifestyle factors.

Results & Analyzes

The main findings of this study show that adherence to lifestyle factors could increase life expectancy at age 50 by 14 years for women and by 12.2 years for men (Fig. 1). In 2014, the life expectancy of a 50-year-old American adult was 33.3 years for women and 29.8 years for men. If they do not follow any of the 5 lifestyle factors, then life expectancy drops to 29 years for women and 25.5 for men. But if they follow the 5 factors, then this life expectancy would rise to 43.1 years for women and 37.6 for men. Unfortunately adherence to a healthy lifestyle (ie, 5 factors) increased from 15% between 1988 and 1992 to only 8% between 2001 and 2006, led mainly by the increase in obesity. And even though US life expectancy increased between 1940 and 2014 (+2 years), its increase was probably slowed by the increase in obesity and the decrease in physical activity.

Over the total period of the follow-up, 42,167 deaths were recorded (of which 13,953 were caused by cancer and 10689 were caused by cardiovascular disease). According to the authors of this study, half of cancer deaths and three-quarters of deaths from cardiovascular disease are attributable to lack of adherence to the factors of healthy lifestyle. On the life expectancy gained by adopting the five healthy lifestyle factors, among women, 30.8% could be attributed to the reduction of cardiovascular diseases, 21.2% to the reduction of cancers and 48.0% to any other cause of mortality. For men, the corresponding numbers are 34.1, 22.8 and 43.1%. Thus, adherence to these 5 factors significantly increases life expectancy by limiting the diseases associated therewith. And as Figure 2 shows, this difference can be made at any age.

Practical Applications

This study shows that simple modifications in one's lifestyle habits (healthier diet, less alcohol consumption, daily physical activity, no smoking and weight control) can allow one to live longer by reducing in particular the risk of cardiovascular disease and cancer. Yet adherence to these 5 factors related to lifestyle is very low (about 8% among Americans). The improvement of drug treatments, care allows us to live longer than before, yet this growth in life expectancy is hampered by sedentary lifestyle and poor eating habits, problems that are easily manipulated and altered.

However, the study has some limitations. First of all, lifestyle factors have been self-reported, so some mistakes are inevitable. Then, each factor was considered of equal importance, while their impact on mortality can be different. Finally, some health problems have not been taken into account such as stress, diabetes, high blood pressure or high cholesterol, although the adoption of a healthy lifestyle will also have a positive impact for these people.

References

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