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Predicting prostate problems. The incidence of prostate cancer among American men increased nearly 200 percent between 1973 and 1992, and with approximately 190,000 new cases and more than 30,000 deaths each year, it is a significant health problem in the United States. Researchers have clearly identified risk factors, such as age, race, and family history, but although they have also associated prostate cancer with high levels of sex hormones, insulin-like growth factor (IGF-1), vitamin D, and calcium, they have been unable to study the effects of cumulative exposure to these substances over time.

Now, a recent longitudinal study by Yuqing Zhang, a MED associate professor of medicine, and colleagues at the BU School of Medicine has established a strong association between high bone mass and increased risk of prostate cancer. Since sex hormones, IGF-1, vitamin D, and calcium are essential for skeletal development and maintenance of bone health, the researchers expected that they would reflect cumulative exposure to these factors. They hypothesized that the higher the bone mass, the more likely the person would be to develop prostate cancer.

Zhang and his colleagues analyzed data from 1,018 white men who participated in the Framingham Heart Study, the landmark epidemiological study funded by the National Heart, Lung, and Blood Institute since 1948 and managed by BU since 1971. X rays of the menís right hands, taken between 1967 and 1970 , were evaluated for bone density. The bone mass was then associated with prostate cancer occurring between 1969 and 1999. The researchers adjusted for factors such as age, height, weight, years of education, alcohol consumption, cigarette smoking, and habitual physical activity.

They found that men whose bone mass was above the median were more than twice as likely to develop prostate cancer as those whose bone mass was in the lowest 25 percent. Although the biologic mechanisms linking this association are not yet understood, the authors surmise that cumulative exposure to sex hormones, IGF-1, vitamin D, and calcium may be implicated.

This research was published in the December 15, 2002, issue of the American Journal of Medicine.

Lost teeth. Nearly 30 percent of Americans between the ages of 35 and 60 have had teeth extracted for one reason or another. Treatment, including replacing missing teeth with a crown or bridge, costs more than .7 billion annually. Working on the assumption that teeth adjacent to those extracted will shift and eventually be lost as well, dentists routinely replace missing teeth. However, ongoing studies by researchers at the Goldman School of Dental Medicine that examine the outcomes of treatment and nontreatment of bounded edentulous spaces (BES), as the empty spaces are known, question the reasoning behind routine tooth replacement.

The research by Professor Raul Garcia and associates used data from the VA Dental Longitudinal Study, which began in 1968. One study followed 104 men who either were missing teeth at the inception of the study, or lost them later. The researchers measured how far adjacent teeth moved over a period of up to 15 years. They found that shifting was minimal, less than one millimeter -- and significantly less for teeth that had been missing since before the study began.

The second study, of 1,231 men ages 31 to 71, looked at the long-term survival of teeth adjacent to BES. Nearly half of the men who were still part of the study in its 21st year (1989) were missing one posterior tooth but had both adjacent teeth still intact. Among those who came into the study at age 50 or younger, nearly twice as many of those who had missing teeth replaced had also lost one or more adjacent teeth -- calling into question the generally accepted notion that failure to replace missing teeth inevitably leads to loss of adjacent teeth.

Garcia and his associates are currently assessing the cost-effectiveness and cost-utility of five alternative treatment strategies for those who are missing teeth. They expect that their analysis will help patients and dentists make better decisions about tooth replacement.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit


15 May 2003
Boston University
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