All Posts tagged epidemiology

Your Risk for Rheumatoid Arthritis

A popular pastime for many older people is to try and figure out their chances of getting one ailment or another. Mayo Clinic researchers have simplified it – they have figured out the lifetime risk of developing rheumatoid arthritis and six other autoimmune rheumatic diseases for both men and women. “We estimated the lifetime risk for rheumatic disease for both sexes, something that had not been done before — separately or collectively,” says Cynthia Crowson Mayo Clinic biostatistician and first author. “Prevalence and incidence rates existed, but prevalence figures underestimate individual risk and incidence rates express only a yearly estimate.”

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The researchers were looking for an accurate basis to offer an easy-to-understand average risk over a person’s lifetime, knowing that risk changes at almost every age. They used data from the Rochester Epidemiology Project, a long-term epidemiology resource based on patients in Olmsted County, Minn. The cohort of 1179, consisted of patients diagnosed between 1955 and 2007, allowed the team to extrapolate the nationwide estimates.

The adult lifetime risk in the United States of having some kind of inflammatory autoimmune disease is 8.4 percent for women and 5.1 percent for men. Based on year 2000 population figures, that means one woman in 12 and one man in 20 will develop one of the conditions in their lifetime. The authors consider that a substantial risk and say their findings should encourage more research on the value of early diagnosis and intervention for people with increased genetic risk of arthritis. They hope the new figures will help in counseling patients and in fundraising efforts to find improved treatments.

The research was supported by the National Institutes of Health.

 

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Low Level of “Good” Cholesterol Associated with Alzheimer’s

A low level of “good” cholesterol is a well-known risk factor for heart disease. A new study by investigators at Columbia University College of Physicians & Surgeons now suggests that a low level of good cholesterol may also raise the risk of developing Alzheimer's disease.

“Low levels of 'good' cholesterol (a.k.a. high-density lipoproteins or HDL) are very common in the United States,” says the study's lead author, Christiane Reitz, MD, PhD, assistant professor of neurology (in the Sergievsky Center and Taub Institute). “If raising HDL can lower a person's risk of developing Alzheimer's disease, that means we may be able to significantly reduce the rate of Alzheimer's disease in the population,” Reitz says, though she cautions that the finding still must be confirmed in other studies.

The study, which appears in the December issue of Archives of Neurology, is co-authored with Jose Luchsinger, MD, MPH, associate professor of medicine and epidemiology, and Richard Mayeux, MD, director of the Gertrude Sergievsky Center and Sergievsky Professor of Neurology, Psychiatry, and Epidemiology.

Previously, the relationship between HDL and Alzheimer's disease had been unclear. Some studies found an association, but others, including one of Reitz's own, found no connection. The new study, Reitz says, follows subjects for a longer period of time than previous studies, resulting in a more accurate account of the number of subjects who ultimately develop Alzheimer's.

After monitoring 1130 elderly residents of northern Manhattan for an average of four years, the researchers found a 40 percent higher incidence of Alzheimer's in residents with low HDL (less than 55 mg/dl). The reason that low HDL is associated with a higher rate of Alzheimer's isn't understood. One possibility is that it works through stroke. “We know low HDL raises the risk of stroke and that stroke is associated with Alzheimer's, so stroke may be the mediator,” Reitz says. “But there's also evidence that HDL works by itself to clear amyloid proteins [the proteins believed to cause Alzheimer's] from the brain.”

Because the study included a large number of African Americans and Hispanics, unlike previous studies that focused on whites, the finding may indicate that low HDL is linked to a high risk of Alzheimer's in many different ethnicities.

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Breastfeeding reduces diabetes risk

Mothers who did not breastfeed their children have significantly higher rates of type 2 diabetes later in life than moms who breastfed, report University of Pittsburgh researchers in a study published in the September issue of the American Journal of Medicine.

“We have seen dramatic increases in the prevalence of type 2 diabetes over the last century,” said Eleanor Bimla Schwarz, MD, MS, assistant professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh. She also has a secondary appointment in epidemiology at the GSPH. “Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breastfeeding also reduces mothers’ risk of developing the disease later in life by decreasing maternal belly fat.”

The study included 2,233 women between the ages of 40 and 78. Overall, 56 percent of mothers reported they had breastfed an infant for at least one month. Twenty-seven percent of mothers who did not breastfeed developed type 2 diabetes and were almost twice as likely to develop the disease as women who had breastfed or never given birth. In contrast, mothers who breastfed all of their children were no more likely to develop diabetes than women who never gave birth. These long-term differences were notable even after considering age, race, physical activity and tobacco and alcohol use.

“Our study provides another good reason to encourage women to breastfeed their infants, at least for the infant’s first month of life,” said Schwarz. “Clinicians need to consider women’s pregnancy and lactation history when advising women about their risk for developing type 2 diabetes.”

Schwarz also is an assistant investigator at the Magee-Womens Research Institute. Co-authors of the study include Jeanette Brown, MD, Jennifer M. Creasman, MPH, and David Thom, MD, PhD, University of California, San Francisco; Alison Stuebe, MD, MSc, University of North Carolina School of Medicine; Candace K. McClure, PhD, University of Pittsburgh; and Stephen K. Van Den Eeden, PhD, Kaiser Permanente, CA.

The research was funded by grants from the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development.

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Fish Oil May Reduce Risk of Breast Cancer

“It may be that the amount of omega-3 fatty acids in fish oil supplements are higher than most people would typically get from their diet,” White said.

However, White cautioned against gleaning any recommendations from the results of one study.

“Without confirming studies specifically addressing this,” she said, “we should not draw any conclusions about a causal relationship.”

Edward Giovannucci, M.D., Sc.D., professor of nutrition and epidemiology at the Harvard School of Public Health and an editorial board member of Cancer Epidemiology, Biomarkers & Prevention, agreed.

“It is very rare that a single study should be used to make a broad recommendation,” said Giovannucci. “Over a period of time, as the studies confirm each other, we can start to make recommendations.”

Still, fish oil continues to excite many, as evidence emerges about its protective effect on cardiovascular disease and now cancer.

Harvard researchers are currently enrolling patients for the randomized Vitamin D and Omega-3 Trial (also called VITAL), which will assess the impact of fish oil supplements and vitamin D on cancer, heart disease and stroke.

The researchers plan to enroll 20,000 U.S. men aged 60 years and older and women aged 65 years and older who do not have a history of these diseases and have never taken supplements.

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Processed Meats Raise Risk of Heart Disease and Diabetes

The researchers, led by Renata Micha, a research fellow in the department of epidemiology, and HSPH colleagues Dariush Mozaffarian, assistant professor in the department of epidemiology and Sarah Wallace, junior research fellow in the department of epidemiology, systematically reviewed nearly 1,600 studies. Twenty relevant studies were identified, which included a total of 1,218,380 individuals from 10 countries on four continents (United States, Europe, Australia, and Asia).

The researchers defined unprocessed red meat as any unprocessed meat from beef, lamb or pork, excluding poultry. Processed meat was defined as any meat preserved by smoking, curing or salting, or with the addition of chemical preservatives; examples include bacon, salami, sausages, hot dogs or processed deli or luncheon meats. Vegetable or seafood protein sources were not evaluated in these studies.

The results showed that, on average, each 50 gram (1.8 oz) daily serving of processed meat (about 1-2 slices of deli meats or 1 hot dog) was associated with a 42% higher risk of developing heart disease and a 19% higher risk of developing diabetes. In contrast, eating unprocessed red meat was not associated with risk of developing heart disease or diabetes. Too few studies evaluated the relationship between eating meat and risk of stroke to enable the researchers to draw any conclusions.

“Although cause-and-effect cannot be proven by these types of long-term observational studies, all of these studies adjusted for other risk factors, which may have been different between people who were eating more versus less meats,” said Mozaffarian. “Also, the lifestyle factors associated with eating unprocessed red meats and processed meats were similar, but only processed meats were linked to higher risk.”

“When we looked at average nutrients in unprocessed red and processed meats eaten in the United States, we found that they contained similar average amounts of saturated fat and cholesterol. In contrast, processed meats contained, on average, 4 times more sodium and 50% more nitrate preservatives,” said Micha. “This suggests that differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats.”

Dietary sodium (salt) is known to increase blood pressure, a strong risk factor for heart disease. In animal experiments, nitrate preservatives can promote atherosclerosis and reduce glucose tolerance, effects which could increase risk of heart disease and diabetes.

Given the differences in health risks seen with eating processed meats versus unprocessed red meats, these findings suggest that these types of meats should be studied separately in future research for health effects, including cancer, the authors said. For example, higher intake of total meat and processed meat has been associated with higher risk of colorectal cancer, but unprocessed red meat has not been separately evaluated. They also suggest that more research is needed into which factors (especially salt and other preservatives) in meats are most important for health effects.

Current efforts to update the United States government's Dietary Guidelines for Americans, which are often a reference for other countries around the world, make these findings particularly timely, the researchers say. They recommend that dietary and policy efforts should especially focus on reducing intake of processed meat.

“To lower risk of heart attacks and diabetes, people should consider which types of meats they are eating. Processed meats such as bacon, salami, sausages, hot dogs and processed deli meats may be the most important to avoid,” said Micha. “Based on our findings, eating one serving per week or less would be associated with relatively small risk.”

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