They looked at reported pain levels in a previous
study of arthritis, then went back to weather records to document
the conditions each day.
It turns out the participants' aches were just a little worse and
joints just a little stiffer when humidity and barometric pressure
"This is something that patients talk about all the time," Dr.
Patience White told Reuters Health. A rheumatologist and vice
president for Public Health Policy and Advocacy for the Arthritis
Foundation, she was not involved in the study.
Osteoarthritis affects about 27 million Americans. Common risk
factors include getting older, being obese, having previous joint
injuries, overuse, weak muscles and genetics.
White said she often sees patients who say they are sensitive to the
"Nobody's bedridden by the weather change," she said, "It's not
severe pain, they just ache more."
More than 60 percent of patients with osteoarthritis say that
weather conditions, such as rain, barometric pressure and
temperature have an impact on their pain and stiffness, according to
the study team, which was led by Desirée Dorleijn, of Erasmus MC
University Medical Center Rotterdam.
Past research attempting to investigate the weather connection had
yielded inconsistent results, so Dorleijn and her colleagues looked
at self-reported hip pain and function in 222 osteoarthritis
patients who participated in a glucosamine sulphate study.
The patients enrolled in the study filled out questionnaires every
three months for two years, including the Western Ontario and
McMasters University Osteoarthritis Index (WOMAC), which is scale
for self-assessment of pain and function. The WOMAC scores range
from 0 to 100, with 0 indicating no pain.
The researchers gathered weather reports for the days the patients
filled out the questionnaires. The information gathered from the
Royal Netherlands Meteorological Institute included average
temperature, wind speed, hours of sunlight, rainfall, humidity and
Patients who underwent surgeries for their arthritis were dropped
during the study; so 188 participants completed the full two years
About 70 percent of participants were
women, averaging about 63 years old.
starting WOMAC pain score was 23.1 and the function score was 35.1.
Those scores improved slightly — each by about 2 points — throughout
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But when the researchers compared weather conditions to pain and
function scores, they found that pain scores worsened by 1 point for
each 10 percent increase in humidity. Function scores worsened by
one point for every 10 hectopascals (0.29 of an inch) increase in
For a change to be considered 'clinically relevant,' it has to alter
the WOMAC score by at least ten points, Dorleijn's team writes in
the journal Pain.
Since variations in humidity and barometric pressure are limited,
they could account for changes of 5 to 6 WOMAC points at the most,
White agreed that requiring a 10-point change to be significant
is the accepted approach to using the WOMAC scale. But that doesn't
mean the pain wasn't real, she said.
"This is about people seeing a little bit of change, whether it's
the humidity or barometric pressure or function or pain," White
Apart from its small size, the study did have some limitations,
White noted. For instance, the patients didn't have severe
osteoarthtitis and the pain was only in one joint. Still, she thinks
it was a good study.
"They did the best they can do, and they did find a little bit of
change. They decided it wasn't significant." She said.
But, she said, just because findings didn't reach statistical
significance from the researchers' point of view, they can be
significant from the patients' point of view.
Pain, online Jan. 24, 2014.
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