all Department of Epidemiology stories

Smoking and solid-fuel-burning in homes in China projected to cause millions of deaths

404132862 — Wed, 01 Oct 2008 14:20:51 -0400

Study shows benefits of eating fish greatly outweigh risks

70652986 — Mon, 26 Mar 2007 05:46:48 -0400

Many studies have shown the nutritional benefits of eating fish (finfish or shellfish). Fish is high in protein and omega-3 fatty acids. But concerns have been raised in recent years about chemicals found in fish from environmental pollution, including mercury, PCBs and dioxins. That has led to confusion among the public - do the risks of eating fish outweigh the benefits?

Researchers from the Harvard School of Public Health (HSPH) tackled that question by undertaking the single most comprehensive analysis to date of fish and health. In the first review to combine the evidence for major health effects of omega-3 fatty acids, major health risks of mercury, and major health risks of PCBs and dioxins in both adults and infants/ young children, the results show that the benefits of eating a modest amount of fish per week - about 3 ounces of farmed salmon or 6 ounces of mackerel - reduced the risk of death from coronary heart disease (CHD) by 36 percent.

Notably, by combining results of randomized clinical trials, the investigators also demonstrated that intake of fish or fish oil reduces total mortality - deaths from any causes - by 17 percent.

Included with the paper, which appears in the Oct. 18, 2006, issue of The Journal of the American Medical Association (http:// jama.ama-assn.org/), is the first comprehensive summary of levels of omega-3 fatty acids, mercury, PCBs and dioxins in various species of fish and other foods, including chicken, beef, pork, butter and eggs.

The research was supported by the National Institutes of Health.

Fatty foods feed heart attacks, researchers say

70652986 — Mon, 26 Mar 2007 06:26:30 -0400

Hold the french fries, doughnuts, and cookies, and save as many as 228,000 heart attacks and deaths from heart disease. That's the message from a team of researchers at the Harvard School of Public Health and Wageningen University in the Netherlands.

"Given the 1.2 million annual [heart attacks] and deaths from coronary heart disease in the United States, near-elimination of industrially produced trans fats might avert between 72,000 and 228,000 coronary heart events each year," the researchers report. Trans fats are also thought to play a role in unexplained sudden deaths and diabetes.

The major sources of trans fats include deep-fried fast foods, bakery products, packaged snack foods, margarines, and crackers. French fries, breaded fish burgers, breaded chicken nuggets, Danish pastries, pies, doughnuts, and cookies are the big offenders. Hamburgers, steaks, lamb chops, and dairy products contain only small amounts of natural trans fats so they don't make the list of "worsts." "The presence of beneficial factors in dairy and these meats may balance the effects of the smaller amount of trans fats they contain," according to Dariush Mozaffarian, lead author of the report that appears in the April 13, 2006, issue of the New England Journal of Medicine.

Ten to 19 percent of the coronary heart disease in the United States (120,000 to 228,000 heart attacks) could be averted by reducing the intake of trans fats, says Walter Willett, head of the research and Fredrick Stare Professor of Epidemiology and Nutrition at the Harvard School of Public Health.

According to the evidence that Mozaffarian, Willett, and their colleagues gathered from studies in the United States and Europe, the "adverse health effects of trans-fatty acids are far stronger on average than those of food contaminants or pesticide residues, which have in some cases received considerable attention. Furthermore, trans fats have no intrinsic health value above their calories."

The research team suggests that trans fats be reduced or eliminated from foods sold in stores, restaurants, and vending machines. Opposing arguments from food manufacturers and restaurants maintain that this would raise costs and lower taste. Recent experiences in Europe indicate that such concerns are overstated, say the researchers. They mention Denmark as a prime example. In that country, all oils and fats used in locally made or imported foods must contain less than 2 percent of industrially produced trans fats.

Stronger evidence found linking Epstein-Barr virus and risk of multiple sclerosis

70652986 — Mon, 26 Mar 2007 06:34:15 -0400

Researchers from the Harvard School of Public Health, Kaiser Permanente, and a team of collaborators have found further evidence implicating the Epstein-Barr virus (EBV) as a possible contributory cause to multiple sclerosis. The study appears in the advance online edition of the June 2006 issue of Archives of Neurology.

MS is a chronic degenerative disease of the central nervous system. Although genetic predisposition plays an important role in determining susceptibility, past studies have shown that environmental factors are equally important.

Low-dose aspirin shown to reduce risk of first stroke in women

70652986 — Mon, 26 Mar 2007 06:19:38 -0400

The Women's Health Study is a large, randomized, double-blind, placebo-controlled trial funded by both the National Heart, Lung and Blood Institute and the National Cancer Institute to evaluate the benefits and risks of low dose aspirin as well as vitamin E supplementation in the primary prevention of cardiovascular disease. The trial included healthy women 45 years of age and older who were monitored for 10 years for first major cardiovascular events.

With regard to aspirin, data addressing these issues in women have been limited. During follow-up, 477 major cardiovascular events were confirmed in the aspirin group as compared to 522 in the placebo group, a 9 percent overall reduction that was not statistically significant. However, the benefit of aspirin within the WHS was due almost entirely to a statistically significant reduction in stroke events without a reduction in heart attack rates. The most consistent benefits were observed among women 65 years of age and older. Among such women, low- dose aspirin use resulted in a 26 percent reduction in risk of major cardiovascular events.

"From a clinical standpoint, the new data suggest that many women are likely to attain a net benefit from preventive aspirin therapy," said Paul Ridker, M.D., and a BWH cardiologist also involved in the WHS clinical trial.

New findings about protection against pneumococcal disease

70652986 — Mon, 26 Mar 2007 06:20:00 -0400

Before the advent of the pneumococcal vaccine, known as Prevnar, S. pneumoniae caused millions of ear infections each year, half a million episodes of bacterial pneumonia, and life- threatening cases of meningitis and bacteremia. Prevnar triggers recipients' immune systems to produce "anticapsular antibodies." However, Prevnar doesn't work well in the developing world, and it is expensive and difficult to manufacture. Moreover, in several studies, use of pneumococcal conjugate vaccines caused non-vaccine strains to become more common, suggesting that Prevnar could eventually become ineffective even in the U.S.

Lipsitch and Malley first conducted epidemiologic studies in unvaccinated toddlers in the U.S., Israel, and Finland, and the incidence of invasive disease from most pneumococcal strains fell by nearly half between one and two years of age. Yet anti- capsular antibody concentrations increased only slightly.

Searching for what caused these results, Malley and Lipsitch were able to elicit long-lasting immunity to pneumococcus in mice independently of any antibodies. When the mice were exposed to live pneumococci, or to a whole-cell vaccine developed in Malley's lab, they were immune to pneumococcal colonization, regardless of their ability to make antibodies. Moreover, mice exposed to a single pneumococcal strain became immune not just to that strain and others. The immunity appeared to arise from an effect on the immune system's CD4+ T-cells.

Their findings suggest that while antibodies protect sufficiently against pneumococcal disease, they may not represent the natural mechanism of protection.

The whole-cell vaccine could protect against all pneumococcal strains, Malley says, and would be a boon for the developing world because it is inexpensive, covers all pneumococcal strains, and does not require refrigeration.

One alcoholic drink per day improves cognitive function among older women

70652986 — Mon, 26 Mar 2007 06:19:51 -0400

According to the study's senior author, BWH's Francine Grodstein, Sc.D., "Much evidence has demonstrated the heart benefits of light alcohol drinking, but less research has focused on cognitive functioning. While we all continue to recommend exercising caution when consuming any type of alcohol, our study suggests that moderate consumption might provide older women some cognitive benefits."

Researchers reviewed data from 12,480 women, 70 to 81 years old, who participated in the Nurses' Health Study. They first collected alcohol consumption data as part of food-frequency questionnaires issued every few years between 1980 and 1998. Alcohol intake was measured in grams of beer, wine and liquor, with moderate consumption - one glass per day - defined as less than 15 grams per day. Then, from 1995-2002, women participated in telephone-based cognitive surveys in which general cognition and verbal memory and fluency were evaluated. Women who consumed less than 15 grams of alcohol per day - moderate drinkers - had better mean cognitive scores than nondrinkers. Researchers also found no significant difference in cognitive functioning among the nondrinkers and those who consumed more than one drink per day. Also, there did not seem to be any substantial difference in the effects of different forms of alcoholic beverages.

"Given our large study population, this body of research is now powerful enough to suggest continued research to ultimately better understand the impact moderate alcohol has on cognitive function," said HSPH's Meir Stampfer, M.D.

Study finds that both weight and exercise are key to longevity

70652986 — Mon, 26 Mar 2007 05:38:51 -0400

Over 115,000 participants who were free of cardiovascular disease or cancer, who were between the ages of 30 and 55 and had filled out biennial health and lifestyle questionnaires between 1976 and 2000, were chosen for the study from the Brigham and Women's Hospital-based Nurses' Health Study. The women answered questionnaires that asked on average how much time was spent per week on moderate physical activities and vigorous physical activities. Women who spent 3.5 hours per week or more exercising were considered physically active. The researchers found that both obesity and physical activity significantly and independently affected mortality. A high level of physical activity did not eliminate the risk of premature death associated with obesity and leanness did not counteract the increased risk in mortality conferred by inactivity. Compared to physically active, lean women, there was nearly a two-and-a-half- fold increase in risk of death for inactive and obese women. The researchers estimated that excess weight (BMI over 25) and physical inactivity accounted for 31 percent of all premature deaths among the study participants with 59 percent of the deaths attributable to cardiovascular disease and 21 percent from cancer among the non-smoking women. "It is clear that both weight and exercise are important for health and longevity," said Frank Hu, lead author of the study and an associate professor of nutrition and epidemiology at the Harvard School of Public Health.

Walking improves cognitive functions in older women

70652986 — Mon, 26 Mar 2007 05:35:24 -0400

In a study, elderly women who engaged in the most activity -- for example, walking at least 6 hours per week -- had a 20 percent decrease in risk of cognitive impairment compared to those who were inactive. they also demonstrated the cognitive functioning of someone three-years younger than their actual age. The findings were published in the Sept. 22, 2004, issue of the Journal of the American Medical Association. “Walking is a popular, accessible and inexpensive activity for older adults that appears to provide many health benefits. In addition to studies showing a reduced risk of heart disease, pulmonary disease and diabetes, a moderate level of walking also appeared to reduce the rate of cognitive decline in our study,” said lead author Jennifer Weuve of the Harvard School of Public Health. “What is most striking is that for older women who are able to engage in several hours per week of physical activity, their cognitive function seemed to be comparable to that of a woman several years younger.” Researchers analyzed the data from 18,766 U.S. women, aged 70 to 81 years, from the Nurses' Health Study.

Close adherence to traditional Mediterranean diet promotes longevity

70652986 — Mon, 26 Mar 2007 05:31:31 -0400

The traditional Mediterranean diet features an abundance of vegetables, legumes, fruits, nuts and cereals and regular use of olive oil (monounsaturated fats), moderate amounts of fish and dairy products (mostly yogurt or cheese), small amounts of red meat (low intake of saturated fats) and moderate consumption of alcohol, usually in the form of wine and consumed at meals. Researchers from the Harvard School of Public Health and the University of Athens Medical School, Athens, Greece, assessed the dietary habits of study participants from all regions of Greece and found that those who strongly adhered to a Mediterranean diet had improved longevity compared to study participants who did not follow that diet as closely. Using a ten point scale to measure adherence to the diet, a two point increase was related to a 25 percent reduction in total mortality among the participants. The study was supported by the Europe Against Cancer Program of the European Commission, the Greek Ministry of Health and the Greek Ministry of Education. The results appeared in the June 26, 2003 issue of the New England Journal of Medicine.

Pregnant women carrying boys eat more than those carrying girls

70652986 — Mon, 26 Mar 2007 05:31:33 -0400

Researchers looked at the diets of 244 pregnant American women via a food frequency questionnaire during the second trimester. They found that women expecting a boy had an eight percent higher intake of protein, a nine percent higher intake of carbohydrates, an 11 percent higher intake of animal fats, and a 15 percent higher intake of vegetable fats than women who were carrying a female embryo. The gender of the newborn had no effect on maternal weight gain, even though weight gain is linked to birth weight.

Study shows acrylamide in baked and fried foods does not increase risk of certain cancers in humans

70652986 — Mon, 26 Mar 2007 05:27:34 -0400

Animal and laboratory studies in the past have indicated that acrylamide, a potentially carcinogenic substance, is found in elevated levels in certain foods, such as potato chips, French fries, cereals and biscuits. Acrylamide appears to form as a result of a reaction between specific amino acids and sugars found in foods when heated to high temperatures. But researchers found that dietary levels of acrylamide are not sufficient to increase the risk of bladder, large bowel and kidney cancer in humans. The researchers assessed the diets of 987 cancer patients and 538 healthy individuals, over a five-year span, to see if there was a link between consumption of foods high in acrylamide and an increased risk of cancer. Each participant filled out a detailed food frequency questionnaire listing a total of 188 different types of foods containing medium to high levels of acrylamide. Lorelei Mucci, a researcher in the Department of Epidemiology at the Harvard School of Public Health said, “It's very reassuring to know that when we looked in detail at the effects of consuming foods containing high levels of acrylamide we found no increased risk for three major cancers. The findings don't condone eating junk food, however.”

Study finds frequent consumption of alcohol linked to lower risk of heart attack in men

70652986 — Mon, 26 Mar 2007 05:27:29 -0400

Men who drank moderate amounts of alcoholic beverages three or more times a week had a risk of myocardial infarction 30 to 35 percent lower than nondrinkers. The observational study, which tracked the drinking habits of nearly 40,000 men over a 12-year period, provides an important clue as to how alcohol helps guard against coronary heart disease, and for the first time, strongly suggests that routine consumption of alcoholic beverages is key. "Even relatively modest amounts of alcohol may be protective if consumed frequently,” said the study's first author, Kenneth Mukamal, of Beth Israel Deaconess Medical Center's Division of General Medicine and Primary Care and assistant professor of medicine at Harvard Medical School. “Our results document that a pattern of regular consumption at least three to four days per week is associated with the lowest risk of heart attacks.” The findings appeared in the Jan. 9, 2003, issue of The New England Journal of Medicine. This research was funded by grants from the National Institutes of Health.

High levels of Epstein-Barr virus antibodies in women linked to risk of multiple sclerosis

70652986 — Mon, 26 Mar 2007 05:17:29 -0400

Multiple sclerosis is a chronic degenerative disease of the central nervous system. Nationwide, there are an estimated 250,000 to 350,000 people with MS. Researchers have long wondered how MS develops and why it targets certain individuals, though they have long suspected that a virus was involved.

Snack foods may increase risk of age-related sight loss

70652986 — Mon, 26 Mar 2007 05:15:26 -0400

Macular degeneration results from the malfunctioning or loss of function of photo-sensitive cells in the retina. According to the Macular Degeneration Foundation, more than 13 million people in the United States are affected; a new case of adult macular degeneration is diagnosed in the U.S. every three minutes. A study in the August 2001 issue of the Archives of Ophthalmology found that a higher intake of specific types of fat, including vegetable, monounsaturated and polyunsaturated fats, may be associated with a greater risk for advanced adult macular degeneration.