Smoking was found to be associated with an increased risk of systemic lupus erythematosus (SLE) among black women, while moderate alcohol consumption significantly reduces the chances of developing the disease, a study reports.
These findings are consistent with studies done in other ethnic groups. The study is the largest to date investigating risk factors for lupus in black women, a population with one of the highest rates of the disease.
The study, “Relationship of cigarette smoking and alcohol consumption to incidence of systemic lupus erythematosus in the Black Women’s Health Study,” was published in the journal Arthritis Care & Research.
Prior epidemiology studies have shown that smoking increases the risk of lupus, while drinking alcohol moderately is protective against the disease.
However, these studies have looked almost entirely at white or Asian populations but not at black people, who are highly susceptible to lupus. People of African and Asian descent are two to four times more likely to develop lupus than people of European origin. Women are also at high risk, developing the disease about nine times more often than men.
This makes the identification of environmental factors that predispose people to lupus especially important for black women, and more so because genetic variation does not sufficiently explain the elevated rates of lupus in this population.
Recognizing this need, researchers set out to investigate the impact of smoking and drinking on the lupus risk among black women.
They conducted a prospective cohort study, one that follows a group of patients over time. The study was based on data from 127 black female lupus patients, at a mean age of 43, from 1995 to 2015, enrolled in the Black Women’s Health Study, a large follow-up study that looks at the health of black women from across the U.S.
At the start of the study in 1995, participants were asked to complete a questionnaire on demographics, health, and lifestyle, including smoking and drinking habits. The women complete follow-up questionnaires every two years.
Smokers were associated with a 45% higher risk of lupus than nonsmokers, although this difference did not reach statistical significance. Lupus risk was greater among current smokers (52%), compared with past smokers (41%); it was also higher among those smoking more cigarettes (20 or more pack-years of smoking), although none of these differences were statistically significant.
In contrast, drinking alcohol (beer, wine, wine coolers, and liquor) was associated with a 29% lower chance of developing lupus for current drinkers and a 21% lower chance for past drinkers, compared with those who never drank. These differences were also not significant.
Nearly all the women in the study were considered “moderate” drinkers, since almost none reported having more than seven drinks a week.
The amount of drinks consumed seemed to matter for protection from lupus. Current moderate drinking, defined as four or more beverages a week, significantly reduced by 57% the likelihood of developing the disease.
Both the increased risk estimated for smokers and the reduced susceptibility for current drinkers is consistent with findings from previous studies.
“The current findings concerning smoking and alcohol consumption were similar to results from studies of White women in the Nurses’ Health Study,” Medha Barbhaiya, MD, the study’s co-first author from the Hospital for Special Surgery in New York, said in a press release.
The relationship between the risk of lupus and both smoking and alcohol intake are biologically plausible and may lead to insights into lupus disease mechanisms, according to the researchers.
Toxic substances from cigarette smoke have been associated with oxidative stress and autoantibody production, and they can directly damage proteins and DNA. Alcohol also inhibits the production of molecules that promote inflammation. In addition, both cigarette smoking and alcohol may cause changes in the expression of genes involved in inflammation and autoimmunity.
“The identification of risk factors for lupus is especially important for Black women because of their high risk of lupus, and studies of other risk factors are in progress,” said Yvette Cozier, PhD, an associate professor at Boston University and co-first author of the study.
Future studies are needed to confirm these findings and establish the biological mechanisms by which smoking and drinking alcohol influence the risk of lupus in this population and others, the researchers concluded.