You don't need to be very happy to avoid an early death from chronic disease, study finds

Happiness is known to correlate with better health. But now, researchers have identified a happiness threshold above which people are less likely to die prematurely of chronic diseases like cancer, diabetes and heart disease.

By comparing data from 123 countries over 15 years, researchers pinpointed a threshold at which mortality declined as well-being increased. Every incremental improvement in well-being above this level was tied to a corresponding drop in the risk of death.

Cancer, heart disease, asthma and other chronic diseases accounted for 75% of non-pandemic related deaths in 2021, according to the World Health Organization (WHO). In the U.S., they're collectively the leading causes of illness, disability and death.

Overall chronic disease mortality decreased in the U.S. between 2010 and 2019, but its prevalence increased among Americans ages 20 to 45 years old, according to a study published in The Lancet earlier this year.

A tipping point

Although previous research assumed a positive association between happiness and health, the goal for this new study, which was published Monday (Oct. 20) in the journal Frontiers of Medicine, was to identify a tipping point at which a higher level of well-being would be associated with measurable health improvements — namely, a reduction in premature deaths due to chronic disease.

To do that, the researchers looked at yearly happiness scores in 123 countries, which they averaged to estimate the national level of subjective well-being.

Related: Can faking a smile make you feel happier?

Respondents from the happiness datasets used in the study were asked to visualize a ladder, with the top representing the best possible life and the bottom the worst. They were then asked to rate their present satisfaction and assess their future on a scale of 0 (bottom of the ladder) to 10 (top of the ladder). This tool, known as the Cantril's life ladder scale, is a well-known social science tool used to gauge life satisfaction.

Researchers then compared this measure of national well-being with chronic disease mortality rates in each country over a period of 15 years (2006 to 2021).

The study identified a happiness threshold of 2.7 on the life ladder scale. Above that threshold, every 1% increase in happiness was associated with a 0.43% decrease in premature deaths from chronic disease.

The average life ladder score among the 123 countries studied was 5.45 between 2006 and 2021, so a 2.7 score suggests participants were "barely coping," study co-author Iulia Iuga, a professor at 1 Decembrie 1918 University in Romania said in a statement.

Health effects of subjective well-being

Although the new study doesn't establish a strict cause-and-effect relationship, scientists have identified several ways well-being could have health benefits.

For one, happiness could reduce the impact of stress, which is strongly associated with the development of many chronic diseases.

"We find that positive emotion can serve as a buffer for stressful experiences," said John Hunter, an assistant professor of psychology at Chapman University in California who was not involved in the research."When you have more positive emotion, you have less stress reactivity, which means that when a stressor hits you, you react less severely," Hunter said. "Your heart rate spikes a little bit less; your blood pressure spikes a little bit less. The way that you release stress hormones also changes."

In addition, people with higher levels of positive emotion often maintain stronger relationships and healthier habits.

"People who are optimistic, people who are happy, people who have a more dynamic, happy social life, people who have a strong sense of life purpose [...] tend to be more proactive about their health," said Dr. Alan Rozanski, a cardiologist and professor of medicine at the Icahn School of Medicine at Mount Sinai who was not involved in the study. "They tend to exercise more. They tend to have better diets. They tend to sleep better."

A useful tool for policymakers

The new study could help policymakers think of happiness as a "public health resource" and use it alongside other key factors to mitigate the impact of chronic diseases on their population, the study authors said in a statement.

Policymakers should aim to push their population’s average well-being above the Cantril threshold while addressing trends and environmental conditions that can worsen chronic conditions, such as obesity, alcohol consumption and pollution, Iuga told Live Science in an email.

In places where well-being is lower, focusing on financing healthcare and improving governance is necessary to unlock the positive health effects of increased happiness, Iuga added.

Because the well-being data used in this study is self-reported, it could be subject to measurement errors, the study noted. In addition, various cultures might assess their level of subjective happiness differently.

The life ladder scale used in this study could also be interpreted as a measure of status rather than emotional happiness, Hunter said. So the question may be capturing people’s economic state and living conditions, rather than their emotional state, he said.