Abstract: BACKGROUND: Clarifying the relationship between dietary magnesium intake and mortality risk in patients with osteoarthritis can provide theoretical basis for optimizing dietary interventions, reducing all-cause mortality and cardiovascular disease mortality, and provide reference value for nutritional management in patients with osteoarthritis.
OBJECTIVE: To assess the association between dietary magnesium intake and all-cause and etiological mortality in adults with osteoarthritis in the United States. 
METHODS: We enrolled data of adults with osteoarthritis from the National Health and Nutrition Examination Survey (conducted by the National Center for Health Statistics under the U.S. Centers for Disease Control and Prevention, it aims to assess the health and nutritional status of the civilian population in the United States) between 2003 and 2020. The association between dietary magnesium intake and mortality in patients with osteoarthritis was evaluated by Cox proportional hazard model and two-stage Cox model. To assess whether the association between dietary magnesium intake and all-cause mortality was consistent across the population and to identify potential high-risk groups, subgroup analyses in terms of age, sex, body mass index, hypertension, diabetes mellitus, physical activity, smoking status, and drinking status were performed and tested for interactions.
RESULTS AND CONCLUSION: (1) A total of 2 868 patients with osteoarthritis were included in this study. During the follow-up period, 699 all-cause deaths, 281 cardiovascular disease deaths and 143 cancer deaths were recorded. After multivariate adjustment, higher dietary magnesium intake was associated with a significantly lower risk of death from cardiovascular disease. Each 1-unit increase in dietary magnesium intake was associated with a 78% lower risk of death from cardiovascular disease (P=0.022 2). The results of quartile analysis of dietary magnesium intake were consistent with this. At the same time, dietary magnesium intake showed a U-shaped association with all-cause mortality and cancer mortality, with turning points at 0.38 g/d and 0.4 g/d, respectively. When magnesium intake was below the threshold, higher intake was significantly associated with lower all-cause mortality [hazard ratio (HR)=0.17, 95% confidence interval (CI)=0.06-0.50] and cancer mortality (HR=0.16, 95% CI=0.01-1.50). Above the threshold, however, magnesium intake was significantly associated with an increase in all-cause mortality (HR=2.94, 95% CI=0.55-15.84) and cancer mortality (HR=26.30, 95% CI=1.46-474.73). Subgroup analyses further verified the robustness of the results. (2) The results suggested that magnesium deficiency might play an adverse role in cardiovascular health. At the same time, there was a U-shaped relationship between dietary magnesium intake and all-cause mortality and cancer mortality, with either too low or too high magnesium intake associated with an increased risk of death. This finding provides new insights into the potential impacts of dietary magnesium intake on cardiovascular disease, cancer, and all-cause mortality, a scientific basis for nutritional interventions in patients with osteoarthritis, and theoretical support for the prevention and management of cardiovascular disease and cancer in China, especially in the context of the high prevalence of cardiovascular disease, where a rational magnesium intake can help to reduce the associated mortality.

Key words: dietary magnesium, osteoarthritis, cross-sectional study, mortality rate, all-cause death, cancer