Causal relationship between dried fruit intake and frozen shoulder: Two-sample Mendelian randomization

Area of Science:

• Nutritional Epidemiology
• Genetic Epidemiology

Background:

• Frozen shoulder, or adhesive capsulitis, is a debilitating condition affecting shoulder mobility.
• Dietary factors, including dried fruit intake, are hypothesized to influence frozen shoulder risk, but causal evidence is lacking.

Purpose of the Study:

• To investigate the potential causal relationship between dried fruit consumption and frozen shoulder using a robust genetic approach.
• To determine if reduced intake of dried fruits is a risk factor for developing frozen shoulder.

Main Methods:

• Utilized two-sample Mendelian randomization (MR) analysis with genome-wide association study (GWAS) data from European ancestry populations.
• Selected genetic variants associated with dried fruit intake and frozen shoulder as instrumental variables.
• Employed inverse variance weighting, weighted median, and MR-Egger methods, alongside heterogeneity and sensitivity analyses.

Main Results:

• The inverse variance weighting analysis indicated a significant inverse causal association between dried fruit intake and frozen shoulder (OR: 0.52, 95% CI: 0.34-0.80, P=0.003).
• No significant heterogeneity or pleiotropy was detected, and sensitivity analyses confirmed the robustness of the findings.

Conclusions:

• Low dried fruit intake is identified as a potential causal risk factor for developing frozen shoulder.
• Findings suggest that adequate consumption of dried fruits may play a protective role against frozen shoulder.