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“… In 2014, with a total health expenditure per capita of $9,402, the United States was ranked first in health expenditure as a percentage of gross domestic product.”

As stated in a publication in the journal Circulation, “The United States, one of the wealthiest nations worldwide, has a shorter life expectancy compared to residents of almost all other high-income countries, ranking 31st in the world for life expectancy at birth in 2015. In 2014, with a total health expenditure per capita of $9,402, the United States was ranked first in health expenditure as a percentage of gross domestic product (17.1%). Yet, the U.S. healthcare system has focused primarily on drug discoveries and disease treatment rather than prevention.” As discussed in my book, The Mind-Gut-Immune Connection, and in many previous posts, these striking numbers reflect that the U.S. medical system is best described as an extremely expensive disease care system, rather than an effective healthcare system, which is hardly a new problem.

Three decades ago, it was already suggested that U.S. major health policies should emphasize reducing unhealthy lifestyles rather than focusing on the development and promotion of increasingly expensive interventions that reduce mortality while allowing morbidity to rise, in other words, keeping increasingly unhealthy people alive. A meta-analysis of 15 studies, including 531,804 participants from 17 countries with a mean follow-up of 13.24 years, suggested that approximately 60% of premature deaths could be attributed to factors related to unhealthy lifestyles, such as smoking, excessive alcohol consumption, physical inactivity, poor diet, and obesity.

“…unhealthy lifestyles and associated metabolic and immunologic alterations are significant risk factors for all these diseases and premature death.”

One of the reasons the U.S. has fallen behind other developed nations is the impact of the chronic non-contagious disease epidemic that has gripped the country for the past 75 years. This epidemic manifests as a range of chronic diseases, including obesity, cardiovascular disease, mental disorders, neurodegenerative disorders, and cancer. These diseases not only frequently co-occur in the same individuals but also are appearing in increasingly younger patients and share low-grade activation of the immune system as a common disease mechanism. It has been widely acknowledged that unhealthy lifestyles and associated metabolic and immunologic alterations are significant risk factors for all these diseases and premature death./p>

To address the impact of adopting low-risk lifestyle factors on life expectancy in the U.S. population, a team of investigators from the Departments of Nutrition and Epidemiology at Harvard T.H. Chan School of Public Health, led by Yanping Li, MD, PhD, and Frank B. Hu, MD, PhD, analyzed extensive data from the Nurses’ Health Study (1980–2014; n=78,865) and the Health Professionals Follow-up Study (1986–2014, n=44,354), publishing the results in Circulation in 2018.

“…life expectancy at age 50 for individuals adhering to all five low-risk factors was 43.1 years for women (reaching an age of 93.1 years) and 37.6 years for men (reaching an age of 87.6 years).”

They defined five low-risk lifestyle factors—never smoking, a body mass index of 18.5 to 24.9 kg/m^2, at least 30 minutes per day of moderate to vigorous physical activity, moderate alcohol intake, and a high diet quality score—and estimated the likelihood of death in the group with these factors compared to a control group without them. For instance, a hazard ratio of 0.26 for adults with five compared to zero low-risk factors indicates that following healthy lifestyles reduced the risk of death by 74% for all-cause mortality, 65% for cancer mortality, and 82% for cardiovascular disease mortality. Based on their findings, the life expectancy at age 50 for individuals adhering to all five low-risk factors was 43.1 years for women (reaching an age of 93.1 years) and 37.6 years for men (reaching an age of 87.6 years). A detailed analysis indicated that combinations of several healthy lifestyle factors had a particularly powerful effect: the greater the number of low-risk factors, the longer the potential life expectancy, regardless of the factors combined.

Despite the decrease in adherence to a low-risk lifestyle pattern among U.S. adults—from 15% in 1988 to 8% in 2006—the life expectancy of Americans has increased from 62.9 years in 1940 to 76.8 years in 2000, with a much slower rate of increase to 79.25 years by 2024. This increase may result from improvements in living standards, medical treatments, and a substantial reduction in smoking. However, the adoption of several unhealthy lifestyle factors likely slowed the earlier gains in life expectancy, particularly due to the obesity and metabolic disease epidemic, and the increase in sedentary lifestyles and decreased physical activity levels. The Harvard study showed that three-fourths of premature deaths from cardiovascular disease and half of premature cancer deaths in the United States could be attributed to a lack of adherence to a low-risk lifestyle.

“…the results of the Harvard study are consistent with recent observations in urban environments…”

In addition to these lifestyle factors, the results of the Harvard study are consistent with recent observations in urban environments like Singapore, where greater access to parks, social ties, smoking restrictions, affluence, and reduced access to unhealthy fast food restaurants have led to the city being referred to as a new Blue Zone (as discussed in an earlier post). Such improvements in urban environment significantly contribute to life expectancy beyond socioeconomic status.

The Harvard study has several limitations: 1) It was a retrospective epidemiological study that shows correlations between lifestyles and longevity but does not establish causality. 2) The study did not consider the role and costs of medical interventions in the observed longevity. The staggering costs of reducing mortality from chronic diseases is higher than in any other developed country. 3) Diet and lifestyle factors were self-reported, a method that can be unreliable. 4) The investigators did not fully consider baseline comorbid conditions, the prevalence of risk genes, and background medical therapies. 5) Mental and spiritual factors, such as a sense of meaning, religious beliefs, compassion, and social interactions—which significantly affect longevity—were not considered.

Despite these limitations, this large epidemiological study is consistent with similar research in industrialized countries, highlighting the crucial importance of easily implementable and inexpensive lifestyle modifications that should be promoted to patients before prescribing an ever-increasing list of medications. Furthermore, it is never too late to adopt this lifestyle modifications as shown by the significant increases in survival rates when these changes are implemented at age 50.