Abdominal obesity heightens the risk for rheumatoid arthritis considerably among women aged 55 years and older regardless of BMI, according to findings presented at the ACR/ARHP 2018 Annual Meeting.
“Being overweight or obese increases the risk of RA among women, particularly among those diagnosed with RA at earlier ages,” the researchers wrote. “Abdominal obesity is more associated with visceral fat and inflammation than overall obesity measured by BMI. We investigated whether abdominal obesity predicts RA risk in two large prospective cohorts, the Nurses’ Health Study and Nurses’ Health Study II.”
Bing Lu, MD, DrPH, associate biostatistician at Brigham and Women’s Hospital and assistant professor of medicine at Harvard Medical School, and colleagues followed women enrolled in the Nurses’ Health Study (n = 48,919) and the Nurses’ Health Study II (n = 47,220) who did not have RA at baseline. Women in the Nurses’ Health Study were aged 40 to 67 years in 1986; women in the Nurses’ Health Study II were aged 29 to 48 years in 1993.
Information on lifestyle and environmental exposures were gathered with biennial surveys. The researchers evaluated abdominal obesity by measuring waist circumference in 1986, 1996 and 2000 for patients in the Nurses’ Health Study and in 1993 and 2005 for patients in the Nurses’ Health Study II. The cutoff point for abdominal obesity, a waist circumference greater than or equal to 88 centimeters, was taken from WHO guidelines for women.
The researchers used a validated connective tissue disease screening questionnaire to categorize incident cases of RA, followed by an assessment of medical records. Positive rheumatoid factor or anti-citrullinated peptide antibodies observed in patients’ medical records were used to identify RA serologic status. Hazard ratios for RA risk were calculated with time-varying Cox proportional hazards models based on data from both groups. Lu and colleagues “repeated analyses restricted to young and middle-aged women (55 years) based on [the] pre-specified hypothesis,” according to the study results.
Through 28 years of follow-up, 803 cases of RA were observed, including 505 cases in the Nurses’ Health Study and 298 cases in the Nurses’ Health Study II. Risk for RA was higher in women with a waist circumference greater than 88 centimeters compared with women who had a lower waist circumference (multivariable adjusted HR, 1.27; 95% CI, 1.10 to 1.47), though additional adjustments for BMI reduced this relationship. The researchers also observed a correlation between BMI and risk for RA among patients with a BMI greater than or equal to 30 kg/m2 compared with a BMI lower than 25 kg/m2 (HR, 1.48; 95% CI, 1.24 to 1.77).
Analyses stratified by serologic status determined that the relationship between waist circumference and RA risk was stronger for seropositive disease than for seronegative disease. Abdominal obesity raised the risk for all RA by 65% and the risk for seropositive RA by 94% among young and middle-aged women ( 55 years). The correlation between abdominal obesity and risk for seropositive RA remained after additional adjustments for BMI (HR, 1.51; 95% CI, 1.01 to 2.25).
“In this prospective cohort study of women followed up to 28 years, abdominal obesity was significantly associated with increased risk [for] developing RA,” the researchers wrote. “Abdominal obesity conferred the greatest risk for seropositive RA among women aged 55 years and older, independent of BMI.” - by Julia Ernst, MS
Lu B, et al. Abstract 1906. Presented at: 2018 ACR/ARHP Annual Meeting, Oct. 20-24, 2018; Chicago.
Disclosures: The researchers report no relevant financial disclosures.