CHICAGO—New research indicates that being obese could increase a person's risk for atrial fibrillation, the most common irregular heart rhythm, by 50 percent, according to a study in the November 24 issue of JAMA.

The prevalence of atrial fibrillation (AF) is expected to increase several-fold in the coming decades, according to background information in the article. Because the onset of AF is associated with considerable illness and a higher risk of death despite various therapies, the identification of potentially modifiable risk factors for AF is important. While obesity has been associated with other heart problems, it has been unclear whether it is a risk factor for AF.

Thomas J. Wang, M.D., of the Framingham Heart Study, Framingham, Mass., and colleagues examined long-term followup data from the Framingham Heart Study to determine if there was an association between body mass index (BMI, a person's weight in kilograms divided by height in meters squared) and the risk of developing AF. The study group included 5,282 participants (average age, 57 years; 2,898 women) without baseline AF. The researchers examined risk for three categories of BMI: normal, defined as less than 25.0; overweight, 25.0 to less than 30.0; and obese, greater than 30.0. A 5'4" woman would have a BMI of 30 if she weighed 174 lbs.; a 6'00" man would have a BMI of 30 if he weighed 221 lbs.

During an average follow-up of 13.7 years, 526 participants (234 women) developed AF. Age-adjusted incidence rates for AF increased across the 3 BMI categories in men and women. In multivariable models adjusted for cardiovascular risk factors and interim heart attack or heart failure, a 4 percent increase in AF risk per 1-unit increase in BMI was observed in men. Obese men had a 52 percent increased risk for AF; obese women, 46 percent increased risk, compared with individuals with normal BMI. The researchers found that the increased risk for AF may be mostly attributable to an associated dilation of the left atrial (upper chamber of the heart).

"...the implication of these results for the population burden of AF may be substantial, because obesity is highly prevalent and potentially modifiable. Thus, even a small decrease in the prevalence of obesity could lead to a large reduction in the incidence of AF," the authors write.

CHICAGO—The number of reported cases of Gillain-Barre syndrome (a rare paralytic disorder) that occur following influenza vaccination has decreased over the past 12 years, according to a study in the November 24 issue of JAMA.

Guillain-Barré syndrome (GBS) is a paralytic disorder in which the body's immune system affects part of the peripheral nervous system, according to background information in the article. The first symptoms include varying degrees of weakness or tingling sensations in the legs followed by progressive weakness. Concerns about the risk of developing GBS following influenza vaccination have been present since an association was first noticed during the 1976-1977 A/New Jersey ("swine influenza") season. Evidence for a relationship between GBS and other influenza vaccines, however, has been less clear. GBS remains the most frequent neurological condition reported after influenza vaccination to the Vaccine Adverse Events Reporting System (VAERS) since its inception in 1990.

Penina Haber, M.P.H., of the Centers for Disease Control and Prevention, Atlanta, and colleagues evaluated trends of reports to VAERS of GBS following influenza vaccination in adults. Reports of GBS in persons 18 years or older following influenza vaccination were evaluated for each influenza season from July 1, 1990, through June 30, 2003. The number of people vaccinated was estimated from the National Health Interview Survey and U.S. census data. Beginning in 1994, active follow-up was conducted to verify GBS diagnosis and obtain other clinical details.

The researchers found that from July 1990 through June 2003, VAERS received 501 reports of GBS following influenza vaccination in persons at least 18 years old. Annual reporting rates of GBS per 100, 000 influenza vaccinations declined from a high of 0.17 in 1993-1994 to a low of 0.04 in 2002-2003, a 4-fold decrease. A GBS diagnosis was confirmed in 82 percent of reports. Preceding illness within 4 weeks of vaccination was identified in 24 percent of reported cases.

Reports of GBS had a different pattern of onset intervals from non-GBS reports, with the median onset interval for GBS reports (13 days) being longer than that of non-GBS reports after influenza vaccination (1 day). Fifty-nine percent of all GBS reports (n = 286) noted symptom onset within 0 to 14 days following vaccination, while 94.5 percent of all non-GBS reports noted symptom onset within the same time interval.

CHICAGO—Adults with diabetes have experienced a 50 percent decline in the incidence rate for cardiovascular disease events in recent decades, according to a report in the November 24 issue of JAMA.

According to background information in the article, deaths caused by cardiovascular disease (CVD) have decreased over the last 50 years. However, it is uncertain whether adults with diabetes, who are at a two- to four-fold increased risk of CVD events (heart attack, coronary heart disease death, and stroke), have experienced a decline in CVD risk.

Caroline S. Fox, M.D., M.P.H., from the National Heart, Lung, and Blood Institute, Framingham, Mass., and colleagues examined data from the Framingham Heart Study in order to determine whether adults with and without diabetes underwent similar declines in CVD. Two sets of study participants, aged 45 to 64 years, were examined: those who participated from 1950 to 1966, and those who participated from 1977 to 1995. Of the 4,118 individuals in the earlier time period, 113 had diabetes; of the 4,063 individuals in the later time period, 317 had diabetes.

OBESITY LINKED TO IRREGULAR HEARTBEAT - A POTENTIALLY FATAL CONDITION