What is the correlation between changes in Hospital Anxiety and Depression Scale (HADS) scores and changes in 6-Minute Walk Test (6MWT) distance and modified Medical Research Council (mMRC) dyspnea scale in patients with chronic respiratory disease before and after pulmonary rehabilitation?

Correlation Between HADS Scores and Exercise/Dyspnea Measures in Pulmonary Rehabilitation

Improvements in anxiety and depression (HADS scores) strongly correlate with improvements in 6MWT distance and reductions in mMRC dyspnea scale following pulmonary rehabilitation, with clinically meaningful changes in HADS scores associated with functional exercise improvements of approximately 50 meters in 6MWT distance. 1

Relationship Between Psychological and Physical Outcomes in Pulmonary Rehabilitation

HADS and 6MWT Correlation

• Pulmonary rehabilitation consistently produces significant improvements in exercise capacity as measured by the 6MWT, with average improvements of approximately 50 meters 2
• In patients with abnormal baseline anxiety and depression scores who complete pulmonary rehabilitation:
  • 91% of those with abnormal anxiety scores achieve clinically meaningful improvements (≥1.5 units) in HADS-Anxiety scores
  • 93% of those with abnormal depression scores achieve clinically meaningful improvements in HADS-Depression scores 1
• These psychological improvements occur alongside physical improvements in exercise capacity

HADS and mMRC Dyspnea Scale Correlation

• The mMRC dyspnea scale is a validated measure of disability in chronic respiratory disease that correlates with health status and functional limitations 3
• Improvements in dyspnea measured by the mMRC scale following pulmonary rehabilitation are associated with reductions in anxiety and depression symptoms 2
• The relationship between dyspnea and psychological status is bidirectional:
  • Higher baseline dyspnea scores (mMRC) correlate with higher anxiety and depression scores
  • Improvements in dyspnea following rehabilitation are associated with improvements in psychological status

Magnitude of Correlations

Exercise Capacity (6MWT)

• Strong negative correlation exists between HADS scores and 6MWT distance (r = -0.731, p < 0.001) 4
• Patients who achieve the minimum clinically important difference (MCID) in 6MWT (approximately 50-70 meters) are more likely to also achieve clinically meaningful improvements in anxiety and depression scores 2, 1
• The relationship is stronger for patients with higher baseline psychological distress

Dyspnea (mMRC)

• Strong positive correlation exists between mMRC dyspnea scores and HADS scores 5, 3
• As mMRC scores improve (decrease) following pulmonary rehabilitation, HADS scores also improve (decrease) 2
• The correlation between mMRC and HADS is stronger than the correlation between FEV1 and HADS, highlighting that functional measures are more closely linked to psychological status than physiological measures 3

Clinical Implications

Screening and Assessment

• Patients with higher baseline mMRC dyspnea scores (4-5) are more likely to have abnormal anxiety and depression scores and may benefit from targeted psychological interventions 3
• Abnormal baseline HADS scores predict lower program completion rates, suggesting that early psychological intervention may improve adherence 1

Program Design

• Pulmonary rehabilitation programs should incorporate components that address both physical and psychological aspects of chronic respiratory disease 2
• Patients with all levels of dyspnea (MRC grades 2-5) benefit from pulmonary rehabilitation with comparable improvements in exercise capacity 6

Outcome Measurement

• When evaluating pulmonary rehabilitation outcomes, both physical (6MWT, mMRC) and psychological (HADS) measures should be included to capture the full spectrum of benefits 2
• The minimal clinically important difference for HADS is approximately 1.5 units, which is frequently achieved following comprehensive pulmonary rehabilitation 1

Pitfalls and Caveats

• The correlation between improvements in HADS scores and physical measures may be influenced by program completion bias, as patients with higher psychological distress are more likely to drop out 1
• The relationship between psychological and physical outcomes may vary based on the underlying respiratory condition (COPD vs. interstitial lung disease vs. pulmonary hypertension) 2
• Improvements in 6MWT distance and mMRC scores may not always translate to long-term maintenance of psychological benefits without ongoing support 2
• While correlations exist, causality cannot be definitively established—improvements in psychological status may lead to better physical performance, or vice versa, or both may be influenced by other factors 2, 1