About 1.3 million Americans are affected by rheumatoid arthritis, an autoimmune disease thought to be caused by genetic and environmental factors.
Strong medication can help prevent joint destruction and painful symptoms.
But there are other things that may affect RA risk and symptoms. In the big picture, these play relatively minor roles in RA (compared to, say, taking the right medication).
Still, here are some factors to keep in mind.
One factor that affects RA is smoking, says Susan Goodman, MD, a rheumatologist at the Hospital for Special Surgery in New York City.
"Smoking clearly has an impactit makes it worse and increases the likelihood of getting it," she says. "There clearly is something about smoking that is a bad actor."
RA nonsmokers have fewer swollen, painful joints than smokers, research suggests. RA smokers are three times as likely to have rheumatoid factora sign of more severe diseaseand twice as likely to have joint damage.
The link between coffee or tea and RA is debatable, Dr. Goodman says.
Research has suggested that decaf coffee (four or more cups a day) can increase the risk of getting RA, but caffeinated coffee has no impact, and tea may reduce risk. Other research found no correlation between decaf and RA.
One issue, though, is that coffee may make some RA medications, such as methotrexate (Rheumatrex, Trexall), less potent.
"There is not a consistent message there," Dr. Goodman notes. Check with your doctor; it may be fine to have a cup of joe.
While research on the topic is scant, there does seem to be a link between weather and RA symptoms. It is likely that barometric pressure and temperature changes have the biggest impact on symptoms.
"Many, many, many people say it, so my sense is it is something we just don't have an appropriate investigational design to test," Dr. Goodman says.
She says any change in climate tends to worsen symptomsso RA patients may fare better when the weather is more consistent.
As with the other factors on the list, the link between RA and allergies may vary from person to person.
Still, there is some research that suggests that people with RA are less likely to have hay fever. And people who do have both may have less-severe RA symptoms.
"My guess is that some of the allergy medications may help with some (RA) symptomatic therapy," Dr. Goodman says. "Or it could just be that people notice RA symptoms less because they are so distracted and miserable with their allergies."
In a recent study in the journal Rheumatology, researchers asked about 1,800 people about their alcohol-drinking habits and RA.
They found that people who had at least one drink three or more days a week were four times less likely to have RA than nondrinkers.
Also, RA patients who did drink tended to have milder symptoms than those who didn't.
The link between vitamin D and RA is tricky.
Research suggests women in the northeastern U.S. are at greater risk of RA than those in sunnier regions. Lack of sun can cause vitamin D deficiency. And vitamin D deficiency has been linked with other autoimmune diseases.
"Vitamin D has a lot of interesting immune effects and metabolic effects and is critical to bone health," Dr. Goodman says. "Whether taking vitamin D will delay the onset or prevent it seems less clear-cut, but it is an important part of overall bone health."
It's tough to predict the impact of pregnancy on RA. Women generally stop taking medication in pregnancy because the drugs may hurt the fetus.
For some, RA symptoms improve or even go into remission, Dr. Goodman says. She attributes this to the fact that the immune system is suppressed during pregnancy.
But others can experience even more pain than they normally do. And those who have a great pregnancy can have a flare-up after they give birth.
There are many benefits to breast-feeding, including a possible reduction in RA risk.
A 2004 study in the journal Arthritis and Rheumatism found that, compared to women who didn't breast-feed, those who spent a total of one to two years breast-feeding had a 20% lower chance of getting RA. Those who did for two years or more had a 50% reduced risk.
A 2008 Swedish study showed similar results. Breast-feeding for up to one year was associated with a 25% reduced risk, and breast-feeding for 13 months or more was linked to a 50% reduction in risk.
The data are a bit up in the air when it comes to hormones and RA.
Studies have not found a link between contraceptives and the risk of RA or the severity of disease.
A 2004 study found that women with irregular menstrual cycles do have a higher RA risk.
"The data aren't completely clear" on this topic, Dr. Goodman says. But hormones may play a role in reducing symptoms. "There is no question that estrogen can decrease pain, so part of some of the perimenopausal flares may be caused by estrogen withdrawal."
There seems to be an anecdotal link between the flu and worsening RA symptoms. And the flu can be especially dangerous for people taking medication that weakens the immune system, which includes most of the drugs used to treat RA.
The CDC recommends flu shots for people with RA. (But not nasal-spray flu vaccines, which contain live viruses.)
One note of caution: Certain RA medicationsmethotrexate, prednisone, and rituximabmay lower the effectiveness of flu shots.