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NEW YORK (Reuters Health) - Despite common complaints that the weather can aggravate fibromyalgia symptoms, a new study finds little consistency in the type of weather conditions linked to worsening of the mysterious pain syndrome.
Furthermore, "the few significant associations that we found (between weather and fibromyalgia symptoms) were very small, too small to affect daily functioning," said Ercolie Bossema, a researcher at Utrecht University in the Netherlands, in an email to Reuters Health.
Bossema added that weather-related symptoms may exist, but "perhaps these factors differ from person to person."
Up to 92 percent of fibromyalgia patients report that certain weather conditions can exacerbate their symptoms - particularly, chronic pain and fatigue, Bossema and her colleagues point out in their study, published in Arthritis Care & Research.
Fibromyalgia is a poorly understood disorder that includes joint pain and tenderness, fatigue and depression and affects an estimated 5.8 million Americans, according to the U.S. Centers for Disease Control and Prevention.
There is no known cause of the disorder, and no surefire way to cure it.
Bossema said that studies examining the influence of the weather on symptoms have not shown an obvious pattern.
Her team asked more than 300 women with fibromyalgia to keep a daily record of their symptoms, sleep and activity for four weeks.
The women rated each measure, such as pain or quality of sleep, on a five-point scale, with five representing "very much" and one "not at all."
The researchers then compared these diaries to each day's weather conditions, including temperature, sunshine, precipitation, humidity and atmospheric pressure.
Overall, the women reported a pain score of 3.35 and a fatigue score of 3.77, which are considered moderate to high.
Higher pain scores were linked to days with less sunshine or higher humidity, but the effects were very small.
For instance, an extra hour of sunshine on a day was tied to a 0.005 decrease on the five-point pain scale.
And a one percent increase in relative humidity was linked with a 0.004 point increase in pain.
With regard to sun, the findings make sense, said Dr. Stuart Silverman, a physician who specializes in fibromyalgia in Beverly Hills, California.
"Everybody feels a lot better in the sun," Silverman said.
"When it's sunny out you go out, and you are tempted to be more active, which reduces your pain too," he told Reuters Health.
For fatigue, symptoms were slightly worse on warmer days and on days with lower humidity, but these changes, again, were small.
Fatigue increased by 0.01 points for each degree Celsius increase in temperature and it dropped by 0.004 points for each one percent increase in humidity.
"Although some significant associations were found, this study provides more evidence against than in support of a uniform influence of weather conditions on daily pain and fatigue in female patients with fibromyalgia," the authors write.
As a group, the women in the study did not report a consistent pattern in their symptoms relative to the weather.
For each weather condition, about one third of the women reported an increase in a symptom, one third showed a decrease and another one third reported no change.
Take, for instance, pain and the amount of sunshine on a given day.
About 32 percent of women reported no consistent change in symptoms if there was less or more sunshine.
Another 30.4 percent of women had greater pain on sunnier days and 37.6 percent of women had less pain on sunnier days.
"Our study indicated that an influence of weather on symptoms of fibromyalgia is not very common," said Bossema.
"However, this does not imply that the symptoms do not exist," she added.
Some women may very well be influenced by the weather, and it is important that future research identify the potential influences on fibromyalgia symptoms.
Silverman said it's understandable why the researchers could not find clear patterns of links between weather and fibromyalgia symptoms.
Symptoms "are unpredictable and change day to day. It's really hard to associate or find any causality, which is one of the problems in this paper," he said.
Although the disorder is unpredictable, women should not be discouraged from seeking help, Silverman added, noting there are medications useful in managing fibromyalgia.
SOURCE: bit.ly/19uOMd4 Arthritis Care & Research, online June 4, 2013.