Beginning in 1988, 530 men and 659 women between the ages of 70 and 79 agreed to participate in a long-term study of their health. Each of the participants was "high-functioning," meaning they did not display any symptoms of disease or other health problems. They did interviews and submitted blood as well as urine samples. Follow-up interviews occurred in 1991 and 1995, and as of 2000, nearly half of the participants had passed away.
Tara Gruenewald of the University of California, Los Angeles, and her colleagues used this data set to examine whether specific combinations of biomarkers proved predictive of mortality. The researchers looked at cardiovascular, neuroendocrine, metabolic and immune biomarkers, including blood pressure or levels of inflammatory cells. By grouping individuals, they looked for sets of biomarkers that led to mortality in more than 70 percent of men or 60 percent of women, because these levels were significantly above expected mortality levels--roughly 51 and 28 percent for men and women, respectively--after 12 years.
The researchers found that 11 of the 13 biomarkers surveyed contribute to elevated male death levels, whereas only six of the 13 contributed to female mortality. The presence of inflammation proteins and abnormal hormonal levels proved most common among those men who died, whereas blood pressure, in combination with other biomarkers such as glycosylated hemoglobin and inflammatory responses, consistently predicted death in women. "The combined presence of a number of these biomarkers at high risk levels may serve as an early warning sign of subsequent mortality," the researchers write in the paper presenting the finding, published online this week in Proceedings of the National Academy of Sciences. "With a focus on prevention, it may be useful to include assays on biomarkers such as C-reactive protein, interleukin-6, fibrinogen, epinephrine and norepinephrine."