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Policy Brief 4 – Quality

Cover of LONELY-EU Policy Brief 4

LONELY-EU Policy Brief No. 4

Hans Rocha IJzerman, Miguel Alejandro Silan

Key findings

  • The LONELY-EU traffic light system rates loneliness measures on cross-EU comparability, construct validity, and content coverage. No measure assessed so far is rated green on all three.
  • Loneliness prevalence estimates from different surveys in the same year (2022) differ by as much as 8 percentage points in some EU member states. In the United States, two reports published in 2025 gave estimates 20 percentage points apart.
  • The Three-Item UCLA Loneliness Scale (T-ILS) is rated green for comparability, with scalar invariance across all 27 EU countries, and green for construct validity, validated in 21 of 27 countries (78%). Its content coverage is rated yellow because it mainly captures emotional distress.
  • The Six-Item De Jong Gierveld Loneliness Scale (DJGLS-6) is validated in 25 of 27 EU countries and rated green for content coverage. It is rated red for comparability, with scalar invariance in only 5 countries and no configural invariance in 14.
  • The brief asks for the traffic light ratings to become the standard for EU loneliness measurement: required in grant applications and policy proposals that use loneliness measures, and updated as new validation evidence comes in.

Executive summary

Not all loneliness measures are equally reliable. With billions in public health resources at stake, EU policymakers need transparent guidance on which measurement instruments produce trustworthy, comparable data across member states. The LONELY-EU traffic light rating system evaluates measures across three critical dimensions—cross-EU comparability, construct validity, and content coverage—enabling evidence-based instrument selection. Current assessment reveals that while several measures perform strongly on individual dimensions, none yet achieves green ratings across all three—a measurement gap the EU SIL Index is being designed to address while providing clear guidance on using available instruments appropriately. This framework ensures policymakers can distinguish between measures suitable for EU-wide monitoring and those requiring more cautious interpretation.

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How to cite

Hans Rocha IJzerman, Miguel Alejandro Silan (2026). The LONELY-EU Evidence Quality Rating System: A Framework for Reliable Loneliness Measurement in EU Policy. LONELY-EU Policy Brief No. 4 Zenodo. https://doi.org/10.5281/zenodo.18786602