Association between serum 25-hydroxyvitamin D status and respiratory tract infections requiring hospital admission: unmatched case-control analysis of ethnic groups from the United Kingdom Biobank cohort

Abstract

Background: Vitamin D status has been found to be inversely associated with risk of respiratory tract infections (RTIs). Although vitamin D status varies by ethnicity, the relationship between serum 25-hydroxyvitamin D (25[OH]D) and RTIs in United Kingdom ethnic groups remains unclear. Objectives: This study aimed to investigate the association between serum 25(OH)D status and hospitalization for RTI in United Kingdom adults. Methods: An unmatched case-control study was conducted using data from United Kingdom Biobank, which includes 500k adults with serum 25(OH)D status and hospital episodes from linked records. Survival analyses and binary logistic regression models were used to explore the association between serum 25(OH)D and RTIs. Results: Of the 36,258 participants included in the analysis, 34% were White, 28% Asian, 19% Black, 11% other, and 7% of mixed ethnicity. The RTI rate was 8.5% (median time to RTI, 14.8 y). Higher serum 25(OH)D (each +10 nmol/L increase) was significantly associated with a 4% lower hazard ratio (HR) for RTI hospitalization [HR: 0.96, 95% confidence interval (CI), 0.94, 0.99]. When stratifying for serum 25(OH)D, compared to those with ≥75 nmol/L (reference), those with <15 nmol/L had a higher HR for RTI hospitalization (HR: 1.33, 95% CI: 1.05, 1.67). Categories 15 to 24 nmol/L, 24 to 49 nmol/L, and 50 to 74 nmol/L were not statistically significant. Logistic regression models supported the above findings. Inclusion of an interaction term for 25(OH)D × ethnicity was trialed in the survival analysis, but the interaction term was not statistically significant. Conclusions: Serum 25(OH)D status <15 nmol/L is associated with 33% higher HR for RTI hospitalization among United Kingdom adults, compared with ≥75 nmol/L. Furthermore, studies are warranted to validate these findings and explore the mechanisms underlying the association between vitamin D status and RTIs in different ethnic groups. Keywords: 25(OH)D; ethnicity; immune health; respiratory tract infection; vitamin D.

AI evidence extraction

Main findings

Among 36,258 participants, higher serum 25(OH)D (per +10 nmol/L) was associated with a lower hazard of RTI hospitalization (HR 0.96, 95% CI 0.94–0.99). Compared with ≥75 nmol/L, serum 25(OH)D <15 nmol/L was associated with higher hazard of RTI hospitalization (HR 1.33, 95% CI 1.05–1.67); intermediate categories were not statistically significant. A 25(OH)D × ethnicity interaction term was not statistically significant.

Outcomes measured

• Respiratory tract infections (RTIs) requiring hospital admission
• RTI hospitalization hazard ratio (HR)

Limitations

• Unmatched case-control design (as stated)
• Interaction term for 25(OH)D × ethnicity was not statistically significant (ethnicity-specific differences not demonstrated)
• Intermediate 25(OH)D categories (15–74 nmol/L) were not statistically significant versus ≥75 nmol/L

{
    "study_type": "case_control",
    "exposure": {
        "band": null,
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "United Kingdom adults (United Kingdom Biobank participants; multiple ethnic groups)",
    "sample_size": 36258,
    "outcomes": [
        "Respiratory tract infections (RTIs) requiring hospital admission",
        "RTI hospitalization hazard ratio (HR)"
    ],
    "main_findings": "Among 36,258 participants, higher serum 25(OH)D (per +10 nmol/L) was associated with a lower hazard of RTI hospitalization (HR 0.96, 95% CI 0.94–0.99). Compared with ≥75 nmol/L, serum 25(OH)D <15 nmol/L was associated with higher hazard of RTI hospitalization (HR 1.33, 95% CI 1.05–1.67); intermediate categories were not statistically significant. A 25(OH)D × ethnicity interaction term was not statistically significant.",
    "effect_direction": "mixed",
    "limitations": [
        "Unmatched case-control design (as stated)",
        "Interaction term for 25(OH)D × ethnicity was not statistically significant (ethnicity-specific differences not demonstrated)",
        "Intermediate 25(OH)D categories (15–74 nmol/L) were not statistically significant versus ≥75 nmol/L"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "unknown",
    "keywords": [
        "25(OH)D",
        "ethnicity",
        "immune health",
        "respiratory tract infection",
        "vitamin D",
        "United Kingdom Biobank",
        "hospital admission"
    ],
    "suggested_hubs": []
}

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