Weight loss of at least 5% over a 3-year period was associated with significantly increased mortality in women at age 90, 95, and 100 years compared with those whose weight remained stable, based on data from more than 50,000 individuals.
Previous studies of later-life weight changes and mortality have yielded inconsistent results driven by considerations of weight loss intentionality, and data on older adults in particular are limited, wrote Aladdin H. Shadyab, PhD, of the University of California, San Diego, and colleagues.
In ain the Journals of Gerontology: Medical Sciences, the researchers reviewed data from the Women’s Health Initiative, a prospective study of factors affecting chronic disease development in postmenopausal women. The study population included 54,437 women who entered the WHI between 1993 and 1998 at ages 50-79 years. The mean baseline age was 69.8 years; 89.5% of the participants were White, 5.7% were Black, 2.7% were Asian, 2.5% were Hispanic/Latino, and the remaining 1.0% were multiracial, American Indian/Alaskan Native, Native Hawaiian/Other Pacific Islander, or unknown.
The primary outcomes were the associations of short-term (3-year) and long-term (10-year) weight changes with survival to ages 90, 95, and 100 years.
A total of 30,647 women survived to at least 90 years (56.3%).
Overall, women with a short-term weight loss of 5% or more of body weight were 33% less likely to survive to age 90 years, 35% less likely to survive to age 95 years, and 38% less likely to survive to age 100 years than were those whose weight remained stable (odds ratios, 0.67, 0.65, and 0.62, respectively).
The associations were stronger in cases of unintentional short-term weight loss. Intentional weight loss from baseline to year 3 was associated with 17% lower odds of survival to age 90 compared to stable weight (OR, 0.83), but unintentional weight loss was associated with 51% lower odds of survival to age 90 (OR, 0.49).
Similarly, women with 10-year weight loss of at least 5% were 40% less likely to survive to 90 years and 49% less likely to survive to 95 years (OR, 0.60 and OR, 0.51, respectively). The sample size was too small to assess the relation of 10-year weight loss with survival to 100 years, and intentionality was not assessed for 10-year weight changes.
By contrast, weight gain of at least 5% had no significant effect on survival to ages 90, 95, or 100 years, but stable weight over time increased the odds of living to ages 90 to 100 years by 1.2-fold to 2-fold compared to either intentional or unintentional weight loss of at least 5%.
The trends in results were similar across body weight categories (normal weight, overweight, and obese as defined by body mass index). Baseline age and smoking status had no significant effect on the results.
Some of the proportion of self-reported intentional weight loss in the study population may have been unintentional, the researchers wrote in their discussion.
“It is important to note that perceived intentionality of weight loss may be influenced by the many societal pressures to lose weight, especially among women, and therefore overestimate the behavioral changes underlying experienced weight loss in older adults,” they said.
The findings were limited by several factors including the potential for inaccurate self-reported weight loss intention, and the likelihood that the mean older age of the population at baseline (older than 60 years) meant that they were more likely to live longer regardless of weight changes, the researchers noted. Other limitations included the primarily White study population, and other residual confounding factors such as ill health that might drive weight loss, the researchers noted.
However, the results were strengthened by the large sample size and long follow-up period, and suggest that “blanket recommendations for weight loss in older women are unlikely to lead to better survival at advanced ages,” they concluded.