Want to live to 90 or beyond? If so, have a good look at the nature of your thoughts about your own life, and whether you tend to think the glass is half empty or half full.

Some fascinating research has just emerged from Harvard demonstrating that having a positive outlook on life can have a major effect on longevity.

The Department of Social and Behavioral Sciences at Harvard Chan School had done a previous study on women showing that optimism – the expectation that things will work out for the best in most circumstances - was linked to a longer lifespan, which, in their view, is living past age 85.

However, that study concerned a white and black population only. Since women from other racial and ethnic groups such as Asian and Latino tend to have higher mortality rates than white people and there’s limited research about the reasons for this, the team, led by PhD candidate Hayami Koga, decided to broaden their participant pool.

They examined data from more than 159,000 participants of the controversial Women’s Health Initiative Study, a study funded by the National Institutes of Health, which had enrolled post-menopausal American women aged between 53-79 in 1993, initially to examine the safety and effectiveness of hormone replacement therapy (HRT).

One of the largest studies to follow women for several decades, the WHI was expected to confirm the safety and benefits of HRT, among other treatments and practices.

Five years into the study of hormone replacement, the Data and Safety Monitoring Board of the WHI shocked the world by calling an abrupt halt to the use of HRT when it became apparent that the 16,000 participants who were taking hormones had an increased risk of developing breast cancer, ovarian cancer, stroke and heart disease. (Journal of the American Medical Association, 2002; 288 (3):321-33).

However, the women continued to be followed for lifestyle information and now have been studied for 26 years. For other scientists like the Harvard team, the WHI represented a goldmine of data for comparing factors around longevity and many other issues, mainly of epigenetics.

Koga and her Harvard colleagues combed through data and survey responses and discovered that the 25 percent of all participants who were the most optimistic were likely to have a 5.4 percent longer lifespan and a 10 percent greater chance of living beyond aged 90, compared to the 25 percent who were the least optimistic.

There were no differences between members of different races or ethnicities, in terms of longevity, and healthy diet and plenty of exercise, which, while important, accounted for less than a quarter of the overall group that lived the longest.

In fact, more than half of the women in the optimistic group achieved exceptional longevity, which is living well past the average age 81.2 years for women (J of the American Geriatric Society, June 8 2022: https://agsjournals.onlinelibrary.wiley.com/doi/10.1111/jgs.17897).

In other words, when it comes to the best way to live a long life, positive thoughts even trump healthy diet and exercise regimes.

The study also bolsters increasing evidence that epigenetic factors like attitude and lifestyle have much more to do with health than genetic factors.

Of all forms of cancer, a family history of breast cancer is usually assumed to be one of the most clearly marked genetic indications that a woman is likely to develop the disease. Recently, many doctors have counseled healthy women with a certain gene to undergo a single or double mastectomy to prevent the development of breast cancer.

Several epidemiologists at the University of Rochester Medical Center in Rochester, New York, questioned this practice after examining data from the WHI.

When they combed through the details of the women taking part in the WHI study who had developed breast cancer, they naturally assumed that they would find a higher incidence of cancer among those who had a family history of the disease.

However, the evidence showed a similar incidence of cancer among those taking HRT, whether or not they had breast cancer in their genetic history. The particulars of a woman’s genetic makeup or a family history of cancer appeared to have nothing to do with it (Epidemiology, 2009; 20: 752–6).

In this case, the environmental stressor – artificial hormones taken regularly – was the major trigger.

All this suggests that these outside factors – most especially the thoughts you maintain as you deal with events and issues in your life – have the most to do with whether you’re going to make it to a ripe old age.

Discovering a passionate purpose, having an optimistic outlook about the future, maintaining close community ties are all the key factors determining whether you are going to celebrate that 100^th birthday.

But the biggest factor of all is your thoughts and keeping that glass filled up with positive expectation and joy.