Disease severity and health-related quality of life across different chronic conditions

OBJECTIVES: Measurements of health-related quality of life (HRQL) are an essential component in overall assessment of health status, particularly in older patients. Nevertheless, how measures of HRQL relate to measures of disease severity is largely unexplored. This study was carried out to explore the relationship between a measure of HRQL and measures of severity of ischemic stroke, Parkinson's diseases (PD), or chronic coronary heart disease (CHD). DESIGN AND SETTING: Cross-sectional analysis of three groups (54 subjects each) of patients aged greater than or equal to 65 years consecutively referred to outpatient clinics for stroke, PD, or CHD, excluding those with cognitive impairment and severs comorbidity. MEASUREMENTS: Severity of stroke, PD, and CHD assessed by Fugl-Meyer Scale (FMS), Webster Rating Scale (WBRS), and total work capacity (TWC, from graded exercise test)? respectively. HRQL was determined by the Sickness Impact Profile (SIP). RESULTS: In PD, WBRS correlated linearly with SIP global score, whereas a significant linear relationship between measures of disease severity and STP score was limited to the least severely diseased stroke (FMS score>160) and the most severely diseased CHD (TWC <700 Kg.m) patients. CONCLUSIONS: In some disease, the relationship between clinical measures of disease severity and HRQL is nonlinear. Thus, depending on initial severity, similar changes in disease severity map have different impacts on HRQL. These findings may help in identifying patients most likely to improve their SIP score substantially, after even small changes in disease severity. However, studies examining the metric properties of SIP across the whole score range are needed to verify whether such improvement really translates into a better HRQL.