Relationship of Health-Related Quality of Life to Symptom Severity in Diabetes Mellitus

Abstract

Our objective was to estimate the effect of greater symptom severity in diabetes mellitus on measures of health-related quality of life in a cross-sectional design in 35 government primary care health centres in Trinidad. Data were gathered on 2,117 subjects with clinical diabetes and analysed for 1,880 (89%). For each scale of the short form 36 (SF-36) questionnaire (a generic measure of health-related quality of life), scores were presented by quartile of symptom severity, measured using the Diabetes Symptom Checklist. Mean (SD) SF-36 scores were 44 (10) for the physical component score (PCS) and 45 (12) for the mental component score (MCS). Greater severity of diabetic symptoms was associated with lower scores on each of the subscales of the SF-36. Comparing lowest and highest quartiles of DSC score, the adjusted difference in PCS was −11 (95% confidence interval −12 to −9) and for MCS −16 (−18 to −14). Our results provide standardised data for health related quality of life in relation to severity of illness from diabetes, these might be used to aid the evaluation of relevant interventions.

Introduction

Non-insulin-dependent diabetes mellitus has emerged as an important health problem in middle-income countries. Many studies have now documented the prevalence of diabetes mellitus and impaired glucose tolerance in different populations [1] but less is known about the health consequences of diabetes in different communities [2]. Evaluating health consequences of diabetes is critical to understanding populations' needs for health care, evaluating the effectiveness of different interventions and ultimately informing resource allocation decisions, which are particularly important in middle and low income countries. Measures of mortality and morbidity have been used traditionally as measures of the health impact of chronic illnesses like diabetes, but these have practical limitations. Routinely available statistics are known to underestimate mortality from diabetes by up to two thirds [3] and methods for assessing clinical complications of diabetes are costly, poorly standardised and difficult to apply in the field [4]. Over the past few years, self-rated measures of health status have attracted increasing attention and it has been suggested that measures of health-related quality of life should be used to inform resource allocation decisions [5]. Interpretation of data describing health-related quality of life requires an understanding of the quantitative relationship between health-related quality of life scores and the underlying severity of illness. Deriving severity-specific quality of life reference data could provide a starting point for evaluating the effectiveness of interventions in economic evaluation.

In Trinidad and Tobago, diabetes mellitus affects between one in five and one in four adults [6], the condition now accounts for some 13% of deaths [7] and diabetes is an important and costly cause of hospital utilisation [8]. In an exploratory study we found that self-reported symptoms and morbidity were common among primary care attenders with diabetes in Trinidad and Tobago [9]. Higher levels of morbidity showed expected associations with older age and longer duration of diabetes but were also associated with indicators of lower socio-economic status including the level of educational attainment, employment status and whether there was a piped water supply in the home 9, 10. In the present study we wanted to extend these observations by evaluating the impact of diabetes-related symptoms on health-related quality of life.