Health for life

Getting older increases Americans risk of death from excessive BMI, finds new study, correcting flaw in earlier obesity paradox research

Obesity kills, giving rise to a host of fatal diseases. This much is well known. But when it comes to seniors, a slew of prominent research has reported an "obesity paradox" that says, at age 65 and older, having an elevated BMI wont shorten your lifespan, and may even extend it. A new study takes another look at the numbers, finding the earlier research flawed. The paradox was a mirage: As obese Americans grow older, in fact, their risk of death climbs.

Ryan Masters, PhD, and Bruce Link, PhD, at Columbia Universitys Mailman School of Public Health, in collaboration with Daniel Powers, PhD, at the University of Texas published the results online in the American Journal of Epidemiology.

The researchers argue that past studies of longevity and obesity were biased due to limitations of the National Health Interview Survey, or NHIS, which provides information on obesity. The survey excludes individuals who are institutionalized, such as in a hospital or nursing home—a group largely made up of seniors. Consequently, the data is overrepresented by older respondents who are healthy, including the relatively healthy obese. Whats more, many obese individuals fail to make it to age 65—and thus do not live long enough to participate in studies of older populations.

"Obesity wreaks so much havoc on ones long-term survival capacity that obese adults either dont live long enough to be included in the survey or they are institutionalized and theore also excluded. In that sense, the survey data doesnt capture the population were most interested in," says Dr. Masters, a Robert Wood Johnson Foundation Health & Society Scholar at Columbias Mailman School and the studys first author.

In his analysis Dr. Masters matched NHIS data on obesity with corresponding records in the National Death Index using data from close to 800,000 adults surveyed between 1986 and 2004. Next he performed statistical adjustments to account for the survey selection biases. The result: risk for death from obesity increases with age.

The finding jibes with countless medical studies that document how obesity takes a cumulative, even compounding toll on the human body. (Exponents of the obesity paradox have explained their counterintuitive results by suggesting that obesitys extra padding protects seniors from fall-related injuries and provides energy reserves during illness.)

"This study should put to rest the notion that its possible to age out of obesity risk, and provides a powerful counterfactual against those who say concern over obesity is overhyped," says Dr. Link, a professor of Epidemiology and Sociomedical Sciences at the Mailman School.

Going forward, Dr. Masters has set his sites on another possible reason behind the obesity paradox—that some of the older obese captured in NHIS data only put on extra weight later in life.

"The recent obesity epidemic hit all age groups at the same time, meaning many of the elderly obese only gained their excess weight in the last 10 years or so," Dr. Masters says. "To account for this fact, I will take a page from studies of cigarette smokers by looking at life years to measure how long someone has been obese rather than whether or not they happen to be obese at the time of a single snapshot survey."

Its estimated that between 10 and 20% of people over the age of 65 suffer from mild cognitive impairment or have been diagnosed with Alzheimer`s disease. By the age of 80 more than half have some loss of memory or functional decline and the trend continues to escalate as the number of baby boomers turned senior citizens explodes.

High levels of vitamin D are associated with protection against bladder cancer, according to a multidisciplinary study coordinated by molecular biologists and epidemiologists from the Spanish National Cancer Research Centre (CNIO), the conclusions of which are published in the Journal of National Cancer Institute (JNCI).

The study has been led by Núria Malats, head of the Genetic and Molecular Epidemiology Group, and Francisco X. Real, from the Epithelial Carcinogenesis Group, at the CNIO.

The authors of the study took blood samples from more than 2,000 individuals - including patients with bladder cancer and control subjects free from the disease - in 18 Spanish hospitals, making of this the largest study carried out to-date in this field. "We have seen that those subjects with the highest levels of 25(OH)D3, a stable form of vitamin D in the blood, are those who showed the lowest risk of suffering bladder cancer. These results indicate that high levels of this vitamin are associated with protection from the illness or, similarly, that low levels are associated with a higher risk of suffering from it", says Malats.

"We have also shown, using in vitro molecular analysis, that vitamin D regulates the expression of a protein - FGFR3 - that takes part in the development of bladder cancer", adds Real.

According to the study, this protective effect is more obvious in those patients with more aggressive cancers. "We observe that high levels of vitamin D diminish, above all, the risk of developing invasive bladder cancer with low levels of FGFR3; which is to say those cancers with the highest probability of metastizing", says André FS Amaral, first author of the study.

The research results suggest that an increase in the dietary or supplementary intake of this vitamin, or via a controlled increase in sun exposure, might be beneficial for the patient in terms of prevention and treatment.

MORE THAN 11,000 NEW CASES EACH YEAR IN SPAIN

Bladder cancer represents a serious public health problem in many countries, especially Spain, where 11,000 new cases are registered each year, one of the highest rates anywhere in the world. In fact, it is the fourth most frequent type of tumour among Spanish males, after prostate, lung and colorectal cancers.

Following diagnosis, patients are continually observed with different follow-up techniques, among them cystoscopy, which requires the introduction of a small camera via the urethra to observe the bladder lining.

This type of follow-up affects the patients quality of life and imposes heavy costs on healthcare authorities, thus further increasing the need to improve prevention strategies faced with this type of cancer.

Recent studies relate vitamin D levels with other types of cancer like breast or colon cancer. Despite this research, it is still not clearly understood which molecular routes are used by this vitamin to exercise its protective effect, or the role it plays in other types of tumours.