In recent years, lifestyle changes that can improve longevity have gained a lot of interest. Among the best studied are the effects of being overweight and obesity on survival at older ages.
A new study published in The Journals of Gerontology examines the association of weight changes and deliberate weight loss on life expectancy at ages above 90 years.
Earlier research shows that participants who become obese in middle age have an increase in mortality risk by over a fifth. Conversely, those obese individuals who lose weight to become overweight during this period show a reduction in mortality risk by over half.
Such weight changes may impact health in later life. Studies such as the Nurses’ Health and Health Professionals Follow-up study showed that losing 2.5-10 kg up to middle age reduced the risk of having any of 11 chronic conditions, as well as of impaired physical or cognitive function, by over a fifth in older women, and over a tenth in older men, respectively.
A serious limitation of this study was the failure to account for voluntary vs. involuntary weight loss, as the former has been associated with lower mortality but the latter with increased risk of death in some studies. Other researchers failed to make any associations between intentional weight loss and mortality in adults or found associations between weight changes in either direction and higher mortality in later life.
Unintentional weight loss may be due to aging-associated reductions in muscle mass. According to one study, weight loss is maximum in the last decade of life, especially in the last three years of life with cancer or the last five years when suffering from cardiovascular disease.
The current study is the first to look at later life weight changes in relation to increased lifespan beyond the age of 90.
What did the study show?
The data was taken from the Women’s Health Initiative, a cohort of over 54,000 aged 61-81. Longitudinal data was analyzed to identify any associations between weight changes and voluntary weight loss and survival rates at 90, 95, and 100 years. The age at baseline was 70 years, with almost 90% being White.
Weight measurements were taken at three points: baseline, year 3, and year 10. This allowed the participants to be categorized as those who had lost 5% or more from the baseline, stable weight (<5%>
At year three from baseline, while about 70% had stable weight, 17% and 15% reported weight loss and weight gain, respectively. Over half of those who lost weight said they did not intend to do so.
At year 10, the average age being ~77 years at this point, less than 50% had stable weight. About 35% had lost weight, and almost 20% gained weight.
Stable weight was more likely among non-Black women who were not current smokers or those with major illnesses. Women who lost weight on purpose were less active, more physically impaired, and more likely to have diabetes or high blood pressure. Weight loss was usually induced by going on a diet, doing more exercise, or joining a weight loss program.
In contrast, unintentional weight loss was more likely among older Black women with a more sedentary lifestyle, higher odds of obesity, and less education, who were more likely to have other major illnesses. Such weight loss was primarily due to illness, poor appetite, or stress.
There were over 30,600 women who lived to or past the age of 90 years. After compensating for confounding factors, the scientists found that weight loss at year 3, as defined above, was associated with a lower chance of living to the age of 90 years, a third lower compared to those with stable weight. Similar reductions in the odds of living to 90 years were observed among those who gained 5% or more body weight.
Weight loss at year ten was linked to 40% lower odds of living to age 90 but 50% lower odds of living to 95.
Among women who lost weight, involuntary weight loss was a stronger marker of lower survival odds at age 90, with this cohort showing less than half the chances of survival compared to those with stable weight. In contrast, those who lost weight on purpose also had lower survival odds, by 17%, but less so than the former.
There was no difference in these associations by body mass index (BMI) category, whether the women were normal weight, overweight, or obese. Weight gain was also not associated with survival odds at later ages.
What are the implications?
Compared to those who lost weight, “stable weight increased the odds of longevity by 1.2 to 2-fold for survival to ages 90 to 100.” Unintentional and intentional weight loss were alike linked to poorer survival into extreme old age, but the former much more strongly than the latter, irrespective of the BMI.
These findings reflect those of earlier studies, such as the Cardiovascular Health Study. However, several randomized controlled trials (RCTs) indicate a lower