Researchers from the US and the UK who analysed health data on over 17,000 women from mid-life to old age found that being overweight or
obese in middle age was linked to a significantly lower chance of enjoying good health in old age, with obese middle aged women having a 79 per cent
The study was the work of researchers from the Harvard School of Public Health (HSPH) and Brigham and Women's Hospital in Boston, Massachusetts, USA, and the University of Warwick in the UK, and is published online in the 29 September issue of the BMJ.
For the study the researchers used data from over 17,000 participants of the Nurses' Health Study, United States, one of the largest and longest running investigations of factors that influence women's health.
All the participants lived at least until the age of 70 and were free from major chronic diseases at mid-life (their mean age was 50 in 1976, the baseline date of the study). They continued to give information on physical function, chronic diseases, cognitive function, and mental health as they approached 70 and over.
The researchers defined "healthy survival" as living to 70 and beyond while at the same time having (1) no history of 11 major chronic diseases, and (2) having "no substantial cognitive, physical, or mental limitations". Thus not only being free of disease, but also having all one's faculties and enough physical and mental ability to go shopping, go up and down stairs and take care of oneself.
"Usual survival" was living to 70 and over but with no particular health status.
After analysing the data the researchers found that:
- 9.9 per cent of the women who lived to the age of 70 and over met the criteria for "healthy survival".
- After taking into account lifestyle and diet, the higher a woman's BMI at baseline, the lower her odds of healthy survival, compared to "usual
survival" (this was a linear relationship with P
- Obese women had 79 per cent lower odds of "healthy survival" compared with lean women (the odds ratio (OR) for this was 0.21, with 95 per cent confidence interval (CI) ranging from 0.15 to 0.29).
- The more weight women gained from age 18 until mid-life, the lower the odds of reaching "healthy survival" at 70 and over.
- Compared to women who were lean at 18 and remained so, the lowest odds of "healthy survival" were among women who were overweight at age 18 and put on 10 kg of weight or more (OR 0.18, CI 0.09 to 0.36).
The researchers concluded that this data is evidence that increased weight in mid-life is "strongly related to a reduced probability of healthy survival among women who live to older ages, and emphasise the importance of maintaining a healthy weight from early adulthood".
One limitation of the study is that the population examined was predominantly white, so these conclusions may not be generalized to all populations.
The study is the first to look at the effect of putting on weight during one's life on the chances of healthy survival into old age. It looks at two growing trends in the US: longevity and weight. In the 100 years leading up to the turn of the millenium, the proportion of Americans living past their mid-70s went up by 26 per cent. Today, nearly two-thirds of Americans are overweight and one third are obese. Other industrialized countries show similar patterns and trends.
Estimates suggest that for the for the first time in human history there will be more people over 65 than under 5 in the world by the year 2040. But as this study suggests, living longer does not necessarily mean living healthier, and it seriously questions the assumption that gaining weight as one approaches middle age does no harm.
However, as lead author Dr Qi Sun, a a researcher in the HSPH Department of Nutrition told the press:
"Since body weight is a modifiable factor, the good news is that healthy aging is not purely the consequence of good genes or other factors that one cannot change."
"If women maintain a healthy weight as adults, they may increase their odds of enjoying a healthy life in their later years," said Sun.
Co-author Dr Oscar Franco, Assistant Clinical Professor of Public Health at Warwick Medical School, described the state of participants who reached the age of 70 free of major chronic disease and substantial cognitive, physical, or mental limitations as "successful aging".
Franco said that as well providing new evidence that carrying extra weight in mid-life is a strong risk factor for lowering the odds of successful survival among older women, the data also suggests that:
"Maintenance of healthy weight throughout adulthood may be vital to optimal overall health at older ages."
"Given that more and more people are surviving to older ages and, at the same time, gaining weight, our results may be particularly important with respect to clinical or public health interventions," said Franco.
"Adiposity and weight change in mid-life in relation to healthy survival after age 70 in women: prospective cohort study."
Qi Sun, Mary K Townsend, Olivia I Okereke, Oscar H Franco, Frank B Hu, and Francine Grodstein.
BMJ 2009;339:b3796, Published 29 September 2009
Additional sources: Harvard School of Public Health, University of Warwick.
Written by: Catharine Paddock, PhD