To study the relationship between daily linoleic acid intake and rheumatoid arthritis (RA).

Data were obtained from the Study of Women's Health Across the Nation (SWAN) 1996-1997 baseline data.Women who met the eligibility criteria were 42~52 years old, had an intact uterus and at least one intact ovary, had not used reproductive hormones in the previous three months and had at least one menstrual period. Women were excluded due to missing information regarding diet and RA. Women suffered from RA and were classified as arthritis group, the rest were classified as control group. Dietary intake was estimated through the 1995 Dietary Frequency Questionnaire. Mann-Whitney U test was used to compare the difference of mean values between groups. Chi-square test was performed to compare differences of rate between groups. Logistic regression analysis were used to exam the relationship between dietary linoleic acid and RA. Restrictive cubic spline analysis was performed to exam non-linear relationships.

Among the 3 121 subjects, 627 (20.09%) suffered from RA.Compared with the control group, the arthritis group had higher linoleic acid intake (Z=-2.403, P=0.016). In the unadjusted covariate model, linoleic acid intake was positively correlated with RA. This relationship still existed in Model 1, which adjusted socio-economic factors. After fully adjusting the socioeconomic and clinical factors, linoleic acid intake was positively correlated with RA risk [ odds ratio(OR)=1.597, 95% confidence interval(CI) (1.211, 2.107)] for the highest quartile spacing compared with the lowest quartile spacing. Restricted cubic spline regression showed that linoleic acid intake and the risk of rheumatoid arthritis presented as polyline-shape. Multivariate analysis showed that age, triglyceride, LDL-C and linoleic acid intake were positively correlated with prevalence of RA [OR=1.051, 95% CI(1.014, 1.089), OR=1.004, 95% CI(1.002, 1.006), OR=1.013, 95% CI(1.005, 1.022), OR=1.009, 95% CI(1.002, 1.017), all P<0.05]. Education level, average exercise index, menstrual state and total cholesterol were negatively correlated with prevalence of RA [OR=0.870, 95% CI(0.803, 0.944), OR=0.878, 95% CI(0.785, 0.981), OR=0.723, 95% CI(0.596, 0.877), OR=0.986, 95% CI(0.978, 0.994), all P<0.05].

The intake of linoleic acid is positively correlated with the RA. Linoleic acid serves as a point of breakthrough in the prevention and treatment of RA.