Interaction of nutritional and inflammatory levels on all-cause mortality among individuals with rheumatoid arthritis: a prospective cohort study.

Background: Malnutrition and systemic inflammation are frequently prevalent in individuals with rheumatoid arthritis (RA). However, limited studies have explored the combined impacts of nutritional and inflammatory levels on all-cause mortality among RA. This study is aimed at investigating these potential associations.

Methods: We involved 2213 RA patients from the National Health and Nutrition Examination Survey (2001-2018). Nutritional risk index (NRI) and systemic inflammatory response index (SIRI) were used to evaluate the nutritional and inflammatory status of participants, respectively. Weight-based Kaplan-Meier survival curves and COX proportional hazard models were employed to ascertain the independent and joint association.

Results: Over a median follow-up of 7.98 years, 544 deaths occurred. Following the adjustment for confounding factors, we found that individuals with moderate/severe malnutrition (HR, 2.13; 95%CI, 1.50-3.03) or high SIRI (HR, 1.49; 95%CI, 1.07-2.07) were independently associated with an increased risk of all-cause mortality. Furthermore, the simultaneous moderate/severe malnutrition and high SIRI further elevated the mortality risk (HR, 2.34; 95%CI, 1.53-3.56). An additive interaction was observed between malnutrition and high SIRI, yielding an excess risk of 0.34 (95%CI 0.06-0.62, P = 0.014), and the attributable proportion for the interaction was 20.9% (95%CI 7.6-34.2%).

Conclusions: This research indicated that malnutrition and high systemic inflammation levels were independent risk factors for the prognosis of RA patients, and co-occurrence can further deteriorate the prognosis. Our findings highlight the importance of maintaining nutrition and anti-inflammation in patients with RA, providing new insights into the prognosis of RA patients.