The benefits of having a healthy lifestyle at middle age can be quite significant, potentially giving us as much as an extra 10 years of living without age-related chronic diseases, according to a study published Wednesday in The BMJ.
And the greater the number of healthy habits we adopt, the longer we’re likely to live free of those diseases, the study also found.
Of course, it’s long been known that certain modifiable lifestyle factors — especially smoking, physical activity, alcohol use, body weight and diet — can affect not only how long we live but whether we develop major chronic illnesses, such as heart disease, type 2 diabetes and certain cancers.
Few studies, however, have taken a close look at how a combination of lifestyle factors might extend the length of time we keep chronic illnesses at bay.
Although U.S. life expectancy has taken deeply troubling declines during the past three years, we are still living longer, on average, than four decades ago. In 2017, the average baby born in the U.S. could expect to live 78.6 years, up from 73.7 years in 1980.
Today, however, many people are living with disabilities and chronic diseases during those extended lifespans — conditions that tend to reduce both the number and quality of the extra years. Indeed, lifestyle factors have been shown to contribute to up to 60 percent of premature deaths in the U.S., shortening life expectancy at age 50 by up to 14 years.
How the study was done
The current study, led by researchers at Harvard University’s T. H. Chan School of Public Health, analyzed data from two large, long-running U.S. studies: the Nurses’ Health Study, which enrolled 121,700 women aged 30 to 55 starting in 1976, and the Health Professionals Follow-up Study, which enrolled 51,529 men aged 40 to 75 starting in 1986. The participants in these studies filled out detailed questionnaires every four years about their health-related behaviors and health status (what illnesses they had).
The authors of the current study excluded from their analysis any participants in the larger studies who had cancer, cardiovascular disease or diabetes at the time they were enrolled in the research projects, as well as people with missing information about lifestyle factors. In the end, their analysis included 38,366 women and 73,196 men.
Each participant received a “healthy lifestyle score” of 0 to 5, based on five factors: never smoking, having a healthy weight (a body mass index, or BMI, of 18.5-24.9), eating a good quality diet (based on Alternative Healthy Eating Index scores), engaging in recommended levels of physical activity, and drinking no more than moderate amounts of alcohol. The researchers then followed the participants for at least 20 years, recording all new diagnoses and deaths from cardiovascular disease, type 2 diabetes and cancer.
After adjusting the data for age, ethnicity, family medical history and other factors linked to those three medical conditions, the researchers found that life expectancy at age 50 was significantly higher for people who adopted four or five low-risk lifestyle factors than for those who adopted none.
At that age, women with a healthy lifestyle score of 4 or 5 lived an average of 9.4 years longer than women with a score of 0 — specifically, 41.1 more years compared to 31.7 years. Similarly, men at age 50 with a healthy lifestyle score of 4 or 5 lived an average of 8.1 years longer than men with a score of 0 — 39.4 versus 31.3 years.
Those higher scores also meant a longer life expectancy free of major chronic diseases — an average of 10.6 more years for the women and 7.6 more years for the men.
For the women, those extra disease-free years included 8.3 without cancer, 10 without cardiovascular disease and 12.3 without diabetes. For the men, it included 6 more years without cancer, 8.6 more years without cardiovascular disease and 10.3 more years without diabetes.
The two groups with the lowest proportion (75 percent or less) of disease-free years ahead of them at age 50 were men and women with obesity (a BMI of 30 or higher) and men who smoked heavily (15 or more cigarettes a day).
The study also found that having a high healthy lifestyle score was associated with longer survival once a chronic disease was diagnosed. Half the study participants with scores of 4 or 5 who developed cancer, for example, survived up to 22.9 years after their diagnosis, whereas half of the patients with scores of 0 survived only up to 11 years.
Limitations and implications
The study is observational, so it can’t prove a direct causal relationship between lifestyle factors, life expectancy and disease-free years. In addition, the participants self-reported their health-related habits, and such reports may not be entirely accurate.
Furthermore, the study looked at only three age-related chronic diseases.
Still, the study’s results are in line with other research that has estimated the effect that a single or small cluster of lifestyle-related risk factors can have on life expectancy — with or without chronic disease.
“Our findings suggest that promotion of a healthy lifestyle would help to reduce the healthcare burdens through lowering the risk of developing multiple chronic diseases, including cancer, cardiovascular disease, and diabetes, and extending disease-free life expectancy,” the authors of the current study conclude.
“Public policies for improving food and the physical environment conducive to adopting a healthy diet and lifestyle, as well as relevant policies and regulations (for example, smoking ban in public places or trans-fat restrictions), are critical to improving life expectancy, especially life expectancy free of major chronic diseases,” they add.
FMI: You can read the study in full on The BMJ website.