The key to long life

A study has shown that men who exercise, are the right weight and do not smoke during retirement increase their chances of living for another 25 years, reported The Daily Telegraph today. The Guardian also covered the story and said the chances of reaching 90 were surprisingly dependent on behaviour from age 70 onwards.

Both newspapers gave a list of adverse factors and their estimated effect on the odds of a 70-year-old man reaching 90. These included high blood pressure, lack of exercise, smoking, obesity, diabetes and a sedentary lifestyle.

This study adds to the body of knowledge on what contributes to exceptional longevity in this age group: that smoking is bad and exercise and a healthy weight are good. However, the study did not look at all the factors that can affect lifespan. Also, the study was carried out in mainly white, middle-class men in the US so the findings may not apply to all 70-year-olds.

Where did the story come from?

Dr Laurel Yates and colleagues from Harvard Medical School, Harvard School of Public Health and the Massachusetts Veterans Epidemiology Research and Information Center carried out the research. The study was funded by the National Cancer Institute and the National Heart, Lung and Blood Institute. The study was published in the peer-reviewed medical journal: Archives of Internal Medicine.

What kind of scientific study was this?

Comparatively fewer men than women live to an advanced age and there is limited information on male longevity. The researchers were interested in what biological and lifestyle factors were associated with exceptional old age in men who had the "potential to live to 90 years".

This study is an analysis of data collected for a larger cohort study called the Physician’s Health Study (PHS). The PHS collected health data from 22,071 generally healthy men when they enrolled between 1981 and 1984 (including blood pressure, height, weight, cholesterol, smoking, alcohol consumption, exercise etc.) Data was then collected annually on changes in the men’s health or lifestyle, and occurrence of chronic diseases, until 2006.

In this particular study, the researchers used the data from 2,350 men from the PHS study. Those who were included were born on or before December 31 1915, didn’t have any serious life threatening diseases and ‘had the potential to live to or beyond 90 years during a 25-year follow-up’ (i.e. they were around 70 years old at the start of the study).

The main interest of the study was survival to age 90, an age the researchers considered to be of “exceptional longevity” and far greater than the expected lifespan (46 to 52 years) of men born in the US between 1900 and 1915. Data on the occurrence of major age-related diseases (cancer, heart disease and stroke) were also collected. A smaller group of the men (686 of them) answered a questionnaire about their physical function and mental health in the 16th year of follow-up.

The researchers compared those who reached 90 years of age with those who did not, for their health data at enrolment, follow-up data, and the occurrence of their outcomes. By doing this, it was possible to identify factors that were associated with "exceptional" longevity in men.

What were the results of the study?

The researchers found that of the 2,357 men aged around 70 when they enrolled in the study, 970 (41%) men survived to age 90.

Those men who did not have high blood pressure, were not sedentary, did not smoke, and were not obese or diabetic at the start of the study had a 54% chance of living to 90 years old.

Men who smoked at the start of the study had only a 25% chance of living to 90 years old. Having a combination of different adverse effects at enrolment reduced the probability of survival even further, e.g. someone who was sedentary, with high blood pressure and diabetes had a 19% chance of surviving to 90 years old, while someone with all five risk factors had only a 4% chance of still being alive 20 years later.

This was a large study and there were other relevant findings: smoking or being overweight was associated with worse physical ability, while moderate, vigorous exercise was associated with better physical ability. Not surprisingly, the men who lived to 90 or older were less likely to have cancer, heart disease, or other diseases associated with high mortality.

What interpretations did the researchers draw from these results?

The researchers concluded that "modifiable healthy behaviours during early elderly years" are associated with both a longer lifespan and good health and function during old age.

What does the NHS Knowledge Service make of this study?

The weaknesses with the study are those described by the researchers themselves:

• The study was limited to white, middle-class men in the US, so the results are unlikely to be applicable to all men in this age group, particularly those from widely different socio-economic backgrounds.
• In their analysis, the researchers took into account a number of factors that may have affected lifespan, but say: "Our analyses did not include a number of other variables that also may influence lifespan."
• Although information was collected from the men annually on changing lifestyle, these data were not used in the analyses which related outcomes to  characteristics at the start of the study. As such the study does not take into account the effects of behaviour changes during the follow-up. Similarly, the study does not capture likely differences between the men in their lifestyles when they were younger (i.e. before study entry).
• All information was collected through self-reporting, i.e. the men told the researchers how much they weighed, what their blood pressure was, about their disease history, their exercise and other lifestyle factors. Studies that use this method and rely on what people say may be subject to reporting bias as it is likely that not all data will be accurate.

Because of these weaknesses, the researchers are cautious in their conclusion and say: "If confirmed in other studies, this would suggest that encouraging favourable lifestyle behaviours, including smoking abstinence, weight management, blood pressure control and exercise, may not only enhance life expectancy but may also reduce morbidity and functional decline in elderly years."

However, as their findings are consistent with other research at younger ages it is unlikely that what is healthy at 40 changes when retirement is reached.