For years, doctors have been advocating a healthy diet, more regular exercise, stress relief, and weight control. However, no study has examined a combination of all these factors with the number of years that one can live free of major chronic disease. This could help communicate the benefits of a healthy lifestyle more convincingly than the commonly reported relative risk of disease with each of these risk factors.
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A Dutch study reported that the presence of all of these healthy lifestyle factors was associated with two extra years of good health compared to those with high-risk lifestyles. Another analysis of multiple cohorts found that those without any lifestyle risk factors lived on average six years more without chronic disease compared with those who had two or more risk factors.
A third study based on the general population showed that without any risk factors, people lived, on average, nine years longer before the onset of any chronic disease.
However, it is not clear what combination of healthy lifestyle factors should be recommended to optimize a healthy lifespan. A new study published April 2020 in the journal JAMA Internal Medicine was motivated by this need to arrive at a quantitative conclusion as to how different combinations of such low-risk factors are linked to disease-free life years.
The researchers designed a prospective study comprising over 116,000 people, including 12 European studies that participated in the Individual-Participant-Data Meta-analysis in Working Populations Consortium.
All participants had no major communicable disease at baseline. The study period was from August 1991 to May 2006. They were scored on each of four lifestyle factors, namely:
- Smoking: never smoked – optimal; quit smoking – intermediate; and current smokers – poor.
- Body mass index (BMI): below 25 (optimal); 25 to 29 (intermediate); and 30 or higher (poor).
- Physical activity: 2.5 hours or more per week of moderate activity or 1.25 hours of strenuous exercise per week (optimal); more active than the poor-activity group (intermediate); and little or no activity outside of work (poor).
- Drinking: 1-14 or 1-21 drinks per week for women and men (1 drink = 10 g ethanol (optimal); no alcohol (intermediate); 15 or 22 drinks or more per week for women and men, respectively.
Each received a score of either 0, for poor risk status, 1 for intermediate-risk, and 2 for optimal risk. The aggregated lifestyle score was examined, and 16 lifestyle profiles were created using various combinations of the risk factors.
The researchers then looked for the number of years lived from 40 to 75 years without major chronic diseases, such as ischemic heart disease, diabetes, stroke, cancer, asthma, chronic obstructive lung disease, heart failure, and dementia.
The participants in the study were, on average, 44 years old, and 61% were women. The total time of follow-up was 1.45 million person-years at risk. During the study period, almost 17,400 people developed one or more chronic health conditions.
The researchers found that the overall healthy lifestyle score was linked to almost ten more years of healthy life in men and 9.4 more in women, compared to men and women with the lowest lifestyle score, respectively. For each additional point in the score, the number of disease-free years went up by almost one year in both men and women.
Four lifestyle profiles were linked to the maximum number of years without disease. All of them had a BMI less than 25, with two or more of the following: never smoked, moderate drinking, physically active. A BMI over 25 was not found in any of the three profiles linked to the shortest lifespan.
People with one of these lifestyle profiles reached the age of 70 years without major disease. Men with zero points had about 22 years of disease-free life between 40 and 75 years, while those with 8 points had about 31. For women, the figures were 22 and 31, respectively.
What do the findings mean?
The study seems to indicate that healthy body weight is an essential component of the healthy lifestyle profile, closely followed by having a more significant number of healthy lifestyle factors. Thus, the effect of each low-risk factor seems to play an additive role. This confirms the results of several other trials that examined a combination of non-smoking, Mediterranean diet, BMI below 25 and physical exercise, or of healthy body weight with the absence of smoking and high blood pressure.
The results of the current study are supported by current knowledge of the ill-effects of obesity on cardiovascular health and metabolic function. Chest and abdominal fat is linked to reduced lung volumes and a higher risk of certain cancers.
Similarly, exercise is associated with a reduction in the risk of type 2 diabetes mellitus, lung and heart disease, and cancer. Smoking is linked to cancer, cardiovascular disease, and lung disease. Drinking affects metabolism and may induce inflammation as well as intoxication with its attendant dangers.
Though the study is an observational one, and the period of follow-up was limited to 75 years, the researchers say, “The results of this study suggest a consistent dose-response association of a higher number of healthy lifestyle factors with the number of disease-free years across the socioeconomic strata, and that various healthy lifestyle profiles are associated with a prolonged healthspan.” This could add weight to the recommendations for a healthy lifestyle.
Nyberg, S. T., et al. (2020). Association of Healthy Lifestyle with Years Lived Without Major Chronic Diseases. JAMA Internal Medicine. doi:10.1001/jamainternmed.2020.0618
Nyberg ST, Singh-Manoux A, Pentti J, et al. Association of Healthy Lifestyle With Years Lived Without Major Chronic Diseases. JAMA Intern Med. Published online April 06, 2020. doi:10.1001/jamainternmed.2020.0618