Posted on 13 May 2022
Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.
Why is this research important: We know that relatively easy and simple lifestyle modifications, such as moderate exercise, eating a healthy diet and getting the appropriate amount of sleep can significantly improve health and lifespan by protecting against diseases of ageing. But how late into life do the benefits of a healthy lifestyle persist? Is a healthy lifestyle more or less important for someone who has already developed multiple age-related diseases?
What did the researchers do: In this study, researchers looked at data from a large study in Japan that followed over 110 000 participants aged 40-79 from across the country. Between years 1988 and 1990, participants answered questionnaires about their lifestyles and medical histories, including the eight components of healthy lifestyle that were considered in the present study. These were: consumption of fruits; consumption of fish; consumption of milk; walking and/or sports participation; body mass index (BMI); smoking status; sleep duration; alcohol consumption. Points were allocated for healthy behaviours to obtain a healthy lifestyle score of 0 to 8. Mortality data was then collected up until the end of 2009. Only the data for 49 000 participants were included in the present study because participants for which health information was incomplete were excluded.
Key takeaway(s) from this research: By the end of the follow-up period, nearly 10 000 participants had died from any cause. All of the modifiable lifestyle factors were associated with a significant decrease in mortality, with three exceptions: fruit and fish consumption in men, and milk consumption in women. A higher lifestyle score was also associated with increased life expectancy. For a score of 7-8, life expectancy at age 40 (that is to say, how much longer a 40 year-old can expect to live on average) increased by 5.3 years for men and 6.2 years for women compared to a score of 0-2. As age increased, healthy lifestyle appeared to benefit men more. When comparing the same scores, life expectancy at age 85 increased by 4.2 years in men and 1.4 years in women.
Researchers then computed the increase in life expectancy at age 40 associated with each lifestyle practice. The full table can be found here. Unsurprisingly, not smoking had a strong effect on life expectancy – a 3.8 and 3.7 year increase for men and women respectively. The biggest disparity between men and women was the effect of alcohol consumption: consuming under 46 grams of ethanol per day was associated with a 1.9 year increase in life expectancy for men, but a 4.9 year increase for women. This difference isn’t necessarily surprising given that women are less able to metabolise alcohol and so are more at risk of disease from a given dose. Additionally, alcohol consumption may be more strongly linked to high socioeconomic status in Japanese men than in women, though the researchers did attempt to control for this. Smoking and alcohol aside, a BMI of between 21 and 25kg/m2 and a sleep duration of 5.5 to 7.4 hours per day were the factors associated with the highest life expectancy gains.
Importantly, the researchers found that people with comorbidities at the start of the study benefited more from healthy lifestyle practices than healthy people. What’s more, increases in life expectancy correlated with the number of comorbidities: the more comorbidities participants had, the more life expectancy they gained from a given number of healthy lifestyle points.
Overall, this study suggests that the benefits of multiple healthy lifestyle practices stack up, and that they persist past the age of 80. It also suggests that these health practices are especially beneficial in those with comorbidities. The fact that this was a follow up study with a large number of participants makes the results more credible, but there are some important limitations. Since this wasn’t a trialled intervention, we can’t be sure to what extent the healthy lifestyle practices actually caused an increase in life expectancy, as we can’t rule out the reverse relationship. People whose health is declining more rapidly may find themselves less able to follow a healthy lifestyle, for example. The study was also conducted in Japan, which has one of the highest life expectancies in the world, so the results of this study may not be as applicable to other populations. Health scores were based on questionnaires from the late 80s, but some participants would have deviated from their reported health practices between then and the end of the study.
Finally, it’s worth noting that someone following a lifestyle practice at the time of the survey is likely to have been following that same practice for much of their life up until that time. The results of this study are likely to represent the effects of a lifetime of consistent health practices, though lifestyle modifications at any stage of life are still likely to have some benefit.
Impact of modifiable healthy lifestyle adoption on lifetime gain from middle to older age: https://doi.org/10.1093/ageing/afac080