Abstract
Aim
Self-rated health, a measure of self-reported general health, is a robust predictor of morbidity and mortality in various populations, including persons with diabetes. This study examines correlates of self-rated health in adults with diabetic peripheral neuropathy (DPN).
Methods
Participants recruited from the UK and USA (n = 295; mean (± sd) age: 61.5 ± 10.7 years; 69% male; 71% type 2 diabetes) rated their health at baseline and 18 months. DPN severity was assessed using the neuropathy disability score and the vibration perception threshold. Validated self-report measures assessed neuroticism, DPN-symptoms of pain, unsteadiness and reduced sensation in feet, DPN-related limitations in daily activities, DPN-specific emotional distress and symptoms of depression.
Results
In the fully adjusted baseline model, younger age, presence of cardiovascular disease and higher depression symptom scores showed likely clinically meaningful independent associations with worse health ratings. Being at the UK study site and presence of nephropathy indicated potentially meaningful independent associations with lower baseline health ratings. These predictors were largely consistent in their association with health ratings at 18 months.
Conclusion
Results identify independent correlates of health ratings among adults with DPN. Future research should investigate the clinical implications of associations and examine changes in these variables over time and potential effects on changes in health perceptions. If these associations reflect causal pathways, our results may guide interventions to target issues that are likely to have an impact on subjectively experienced health as an important patient-reported outcome in DPN care.
Introduction
Patient-reported outcomes are increasingly important in clinical practice and clinical trials to capture valuable information about health status and burdens of treatment, not otherwise reflected in objective or biological measures. One central patient-reported outcome is self-rated health, a measure of a person’s perception of their general health that is thought to incorporate social, psychological and biological aspects of the self [1]. Despite robust controls for potential confounding variables, self-rated health consistently predicts morbidity and mortality [2], including among individuals with diabetes [3]. For example, health ratings predict diabetic foot ulceration and amputations among individuals with type 2 diabetes after adjustment for established risk factors and clinical history [4]. Diabetic peripheral neuropathy (DPN) has been previously associated with lower health ratings among people with diabetes [5], and further investigation is warranted to more fully assess this relationship in the context of other potential health status and psychosocial influences on health ratings.
DPN is the most prevalent complication of diabetes, affecting up to 50% of individuals with diabetes [6], leading to severe morbidity and high healthcare costs [7]. Individuals experience impaired quality of life (QoL) due to neuropathic pain, loss of sensation leading to poor balance, falls, foot deformities, and high rates of ulceration and amputation [8]. DPN is also a source of significant emotional distress, with DPN symptoms and associated limitations in functioning accounting for nearly half of the variance in depression symptom scores [9,10]. DPN-related unsteadiness is one of the strongest predictors of depression symptoms in this population [9,10] and is an important determinant of non-adherence to offloading [11]. An earlier cross-sectional study linked DPN symptoms of numbness and loss of sensation with lower overall self-rated health [5], but unsteadiness was not evaluated and clinical indicators of DPN severity were not available.
The current study explores independent correlates of health ratings over time among individuals with DPN. We hypothesized that increased DPN severity would be associated with lower self-rated health, independent of demographics, other health-related characteristics, and neuroticism, a trait measure of the general tendency to experience negative affective states, which could bias health self-ratings [12]. We next sequentially adjusted this relationship for DPN-related symptoms, DPN-related limitations in daily activities, and depression symptoms and DPN-emotional distress to gain insight into the potential role of these factors as mechanisms linking DPN severity to health ratings. We hypothesized that the association between DPN severity and health ratings would be primarily explained by DPN symptoms, DPN-related limitations in daily activities and emotional distress based on prior findings linking these variables to depression [9,10] and overall quality of life self-ratings in this sample [13]. This is consistent with a conceptual framework that views symptoms, functional limitations, and emotional distress as outcomes of DPN severity that are important to individual health [8]. We examined correlates of health ratings obtained at baseline and ~ 18 months later. A better understanding of correlates of self-rated health in people with DPN may shed light on the factors that could influence perceptions of health among people with DPN and provide evidence for the clinical significance of self-rated health as a patient-reported outcome.
Research design and methods
Participants and procedures
A total of 295 individuals with type 1 or type 2 diabetes and moderate-to-severe DPN who provided health ratings at baseline and 18 months were included in the current analyses. These individuals were recruited from specialist diabetes centres in the UK (Manchester) and USA (Baltimore, MD and State College, PA) for participation in an 18-month study examining the psychological determinants of foot self-care adherence and foot ulceration. Further details of this sample have been described previously [9,10,14]. Two clinical tests established the presence of DPN in accordance with diagnostic guidelines [6]: the neuropathy disability score (NDS) and the vibration perception threshold (VPT; see Measures). Individuals were included if VPT ≥ 25 V and NDS ≥ 3. Those who had significant peripheral vascular disease (less than palpable pulse per foot and/or history of bypass surgery), history of major amputation (more than a single digit), advanced diabetes complications (e.g. end-stage renal disease), other severe medical conditions (e.g. stroke), or insufficient English comprehension were excluded.
The study was approved by the Central Manchester Research Ethical Review Committee and the institutional review boards at the Johns Hopkins University and the Pennsylvania State University, and informed consent was obtained from all participants.
Measures
Demographic, disease and trait characteristics
Demographic and clinical characteristics included age, sex, education, marital status, type of diabetes, diabetes complications (retinopathy, nephropathy and cardiovascular disease), and number of comorbid illnesses. Neuroticism was measured by the Big Five Inventory (eight items) [15], which showed good internal consistency in this sample (α = 0.82).
DPN severity
The VPT was assessed at the great toe in both feet in triplicate, using a neurothesiometer (Horwell, Nottingham, UK). The NDS was derived from examination of pain, vibration, temperature sensation and Achilles reflex. A score of 0 represents a normal nervous system examination and the maximum score was 10 [16].
DPN-related symptoms and functioning
The NeuroQoL, a measure of quality of life developed specifically for individuals with DPN [13], includes neuropathic symptoms of reduced feeling (three items), pain (seven items) and unsteadiness (three items), DPN-related limitations in daily activities (three items) and DPN-emotional distress (11 items). Higher scores indicate greater endorsement of symptoms, limitations and DPN-emotional distress. Internal consistency for DPN symptoms, DPN-related limitations in daily activities, and DPN-emotional distress was good to excellent (α = 0.86−0.90).
History of diabetic foot ulceration
Individuals were coded as having a positive history of diabetic foot ulceration at baseline if they self-reported a prior foot ulceration (an open sore on your foot; those answering in the affirmative were verified by examination of medical records), or had an active foot ulceration (a full-thickness skin break below the malleoli) as determined by a study podiatrist.
Emotional distress
DPN-emotional distress assessed using the NeuroQoL captured individuals’ perceived interpersonal-emotional burden specific to DPN (physical/emotional dependence on others; being treated differently from other people as a result of DPN) and has been shown to be distinguishable from general emotional well-being in its association with objective measures of DPN severity [13]. Internal consistency is described above. Depressive symptoms were assessed using the 7-item Hospital Anxiety and Depression Scale (HADS) [17], and higher scores indicate greater severity of symptoms. Internal consistency was good (α = 0.84).
Self-rated health
Single-item health ratings were measured using the SF-12 [18] at baseline and 18 months. Participants were asked, ‘In general, would you say your health is excellent, very good, good, fair, or poor?’ Responses were rated on a scale of 1 to 5, and were coded so that higher scores indicate better health.
Statistical analyses
Descriptive statistics were assessed for all study-related variables. Bivariate associations were examined using Pearson’s r for continuous study variables, and t-tests or chi-squared tests for categorical study variables. Six regression models were run to explore the association between hypothesized correlates and baseline health ratings, as follows: (1) covariates (demographics, health-related characteristics and trait neuroticism); (2) NDS and VPT neuropathy severity scores); (3) history of diabetic foot ulcer; (4) DPN symptoms; (5) DPN-related limitations in daily activities; and (6) depression symptoms and DPN-emotional distress. Sequential examination of the independent contributions of these variables across six regression models allowed us to examine our expectation that the association between DPN severity and health ratings would be primarily explained by DPN symptoms, DPN-related limitations in activities and emotional distress variables. One regression model (model 7) tested whether factors were consistently associated with self-rated health over time. We considered a mean change of 0.20 in self-rated health in relation to a meaningful change in the independent variable as clinically significant based on previous research [19,20]. Relationships were considered likely to be clinically meaningful when unstandardized coefficients indicated at least this magnitude of association and confidence intervals (CIs) included values largely above this threshold. When 95% CI crossed this threshold, we considered these associations potentially meaningful. Data were considered to be missing at random, with no demographic or illness differences between those missing and not missing data. Nine variables had some missing values, ranging from 1 missing value for the presence of cardiovascular disease to 9 for the presence of retinopathy. We ran multiple imputation analyses for baseline models to correct for missing data. Parameters were estimated within each imputed data set individually and then combined using Rubin’s rules [21]. Analyses were conducted using Stata 16.1 (StataCorp., College Station, TX, USA).
Results
Sample characteristics
Descriptive characteristics of the study sample are presented in Table 1. The majority of participants were male, older adults diagnosed with type 2 diabetes. In this population with DPN, retinopathy (43%) and cardiovascular disease (35%) were the most common additional diabetes complications reported. At baseline, 38% of subjects reported a previous or active diabetic foot ulcer. The most commonly endorsed self-rated health score indicated ‘fair’ health (33%), followed by ‘good’ health (32%). The mean HADS score (4.9 ± 3.8) was within the ‘normal’ range [17], and the mean DPN-emotional distress score (2.3 ± 1.2) indicated average distress [13].
Table 1.
Sample characteristics
| Characteristics | UK (n = 179) | USA (n = 116) | Total (n = 295) |
|---|---|---|---|
| Female | 52 (29) | 38 (33) | 90 (31) |
| Age (years) | 61.2 ± 11.3 | 61.9 ± 9.7 | 61.5 ± 10.7 |
| Education | |||
| Primary | 7 (4.0) | 1 (0.9) | 8 (2.7) |
| Secondary | 95 (53) | 48 (41) | 143 (48) |
| Some college | 49 (27) | 16 (14) | 65 (22) |
| College graduate | 13 (7.3) | 30 (26) | 43 (15) |
| Postgraduate | 11 (6.1) | 18 (16) | 29 (10) |
| Missing | 4 (2.2) | 3 (2.6) | 7 (2.4) |
| Marital status (living alone) | 57 (32) | 29 (25) | 86 (29) |
| Type 2 diabetes | 114 (64) | 96 (83) | 210 (71) |
| Retinopathy | 77 (43) | 49 (42) | 126 (43) |
| Nephropathy | 26 (15) | 21 (18) | 47 (16) |
| Cardiovascular disease | 56 (31) | 47 (41) | 103 (35) |
| Concomitant disorders | 0.7 ± 0.9 | 1.5 ± 1.3 | 1.0 ± 1.1 |
| DPN severity | |||
| Neuropathy disability score | 7.3 ± 2.3 | 7.5 ± 2.2 | 7.4 ± 2.3 |
| Vibration perception threshold | 39.6 ± 9.5 | 45.4 ± 8.4 | 41.8 ± 9.5 |
| Foot ulcer: ever/current | 54 (30) | 59 (51) | 113 (38) |
| Neuroticism | 2.7 ± 0.7 | 2.7 ± 0.6 | 2.7 ± 0.7 |
| Pain | 1.9 ± 0.8 | 1.9 ± 0.7 | 1.9 ± 0.8 |
| Reduced feeling | 2.6 ± 1.5 | 3.5 ± 1.3 | 2.9 ± 1.5 |
| Unsteadiness | 2.1 ± 1.2 | 2.4 ± 1.1 | 2.2 ± 1.1 |
| Limitations daily activities | 2.3 ± 1.3 | 2.9 ± 1.3 | 2.5 ± 1.4 |
| Depression symptoms | 5.1 ± 4.1 | 4.7 ± 3.4 | 4.9 ± 3.8 |
| DPN-emotional distress | 2.2 ± 1.2 | 2.6 ± 1.1 | 2.3 ± 1.2 |
| Baseline self-rated health | 2.7 ± 1.1 | 2.8 ± 0.9 | 2.8 ± 1.0 |
| 18-month self-rated health | 2.6 ± 1.0 | 2.8 ± 0.9 | 2.7 ± 1.0 |
Values are given as n (%) or mean (± sd). DPN, diabetic peripheral neuropathy.
Site comparisons (UK vs. USA) indicated that US participants were more likely to have type 2 diabetes, reported more comorbid disorders, more diabetic foot ulcer, had higher VPT scores indicative of more severe DPN, and lower self-reported functioning as assessed by the NeuroQoL.
Summary of findings
Baseline analyses
Results of the six stepped regression models are shown in Table 2. Model 1 examined demographic and disease correlates of baseline self-rated health. Younger age (0.02; 95% CI 0.01, 0.03), the presence of cardiovascular disease (−0.39; 95% CI −0.61, −0.16) and higher levels of neuroticism (−0.48; 95% CI −0.65, −0.32) each showed likely clinically meaningful independent relationships with lower baseline self-rated health. Being in the UK (0.27; 95% CI 0.04, 0.50), having type 2 diabetes (−0.29; 95% CI −0.56, −0.01), the presence of nephropathy (−0.30; 95% CI −0.59, −0.001) and comorbidities (−0.12; 95% CI −0.22, −0.01) indicated potentially meaningful associations with lower health ratings. When NDS and VPT scores were added to the model (model 2), increases in NDS scores indicated a potentially clinically meaningful association with lower baseline mean health ratings (−0.06; 95% CI −0.11, −0.01). The addition of foot ulcer history in model 3 led to imprecise estimation (i.e. small coefficient, large confidence interval) of the association of history of foot ulcers with baseline self-rated health (−0.05; 95% CI −0.29, 0.20), from which no substantive conclusions could be drawn. When DPN symptoms assessed by the NeuroQoL were added to model 4, increases in unsteadiness (−0.16; 95% CI −0.28, −0.04), pain (−0.16; 95% CI −0.31, −0.02), and reduced feeling (−0.11; 95% CI −0.20, −0.01) scores indicated potentially meaningful associations with lower health ratings. Notably, the addition of DPN symptoms attenuated the effect of NDS on baseline self-rated health. When DPN-specific limitations in daily activities scores were added to model 5, a potentially clinically meaningful association with reduced health ratings was found (−0.12; 95% CI −0.21, −0.04). Further, the addition of limitations to the model attenuated the associations between reduced feeling, pain and unsteadiness with baseline self-rated health. Finally, when depression and DPN-emotional distress were included in model 6, depression symptoms showed a likely clinically meaningful negative association with baseline self-rated health (−0.09; 95% CI −0.12, −0.05). The addition of depression and DPN-emotional distress variables attenuated the effect of DPN-specific limitations in daily activities, and further attenuated the effects of DPN symptoms, on self-rated health. In this final model, younger age (0.02; 95% CI 0.004, 0.03), the presence of cardiovascular disease (−0.32; 95% CI −0.53, −0.12), and depression symptoms each indicated likely meaningful independent associations with lower self-rated health, while being in the UK (0.23; 95% CI 0.01, 0.46) and the presence of nephropathy (−0.19; 95% CI −0.46, 0.07) indicated potentially meaningful independent associations with lower health ratings.
Table 2.
Regression Models Predicting Self-Rated Health at Baseline
| Variable | Model 1 Coefficient (95% CI) | Model 2 Coefficient (95% CI) | Model 3 Coefficient (95% CI) | Model 4 Coefficient (95% CI) | Model 5 Coefficient (95% CI) | Model 6 Coefficient (95% CI) |
|---|---|---|---|---|---|---|
| Demo/Disease/Trait | ||||||
| Country | 0.27 (0.04, 0.50) | 0.25 (0.01, 0.48) | 0.25 (0.01, 0.49) | 0.31 (0.08, 0.54) | 0.34 (0.11, 0.57) | 0.23 (0.01, 0.46) |
| Female | −0.08 (−0.32, 0.15) | −0.08 (−0.32, 0.16) | −0.08 (−0.32, 0.16) | −0.01 (−0.23, 0.22) | 0.01 (−0.22, 0.23) | 0.03 (−0.19, 0.24) |
| Type 2 diabetes | −0.29 (−0.56, −0.01) | −0.31 (−0.59, −0.03) | −0.31 (−0.59, −0.03) | −0.21 (−0.48, 0.06) | −0.21 (−0.47, 0.05) | −0.18 (−0.43, 0.08) |
| Age | 0.02 (0.01, 0.03) | 0.02 (0.01, 0.03) | 0.02 (0.01, 0.03) | 0.02 (0.004, 0.03) | 0.02 (0.004, 0.03) | 0.02 (0.004, 0.03) |
| Retinopathy | −0.17 (−0.39, 0.06) | −0.14 (−0.37, 0.09) | −0.13 (−0.36, 0.10) | −0.09 (−0.31, 0.13) | −0.09 (−0.31, 0.12) | −0.09 (−0.29, 0.12) |
| Nephropathy | −0.30 (−0.59, −0.001) | −0.28 (−0.58, 0.01) | −0.28 (−0.57, 0.02) | −0.23 (−0.51, 0.05) | −0.21 (−0.49, 0.07) | −0.19 (−0.46, 0.07) |
| Cardiovascular disease | −0.39 (−0.61, −0.16) | −0.40 (−0.62, −0.17) | −0.40 (−0.63, −0.17) | −0.34 (−0.55, −0.12) | −0.32 (−0.53, −0.11) | −0.32 (−0.53, −0.12) |
| Comorbidities | −0.12 (−0.22, −0.01) | −0.11 (−0.22, −0.01) | −0.11 (−0.22, −0.01) | −0.08 (−0.18, 0.02) | −0.09 (−0.19, 0.01) | −0.09 (−0.19, 0.0002) |
| Neuroticism | −0.48 (−0.65, −0.32) | −0.49 (−0.65, −0.32) | −0.49 (−0.65, −0.32) | −0.34 (−0.50, −0.18) | −0.31 (−0.48, −0.15) | −0.17 (−0.33, 0.001) |
| DPN severity | ||||||
| NDS | −0.06 (−0.11, −0.01) | −0.06 (−0.11, −0.004) | 0.01 (−0.05, 0.06) | 0.003 (−0.05, 0.06) | 0.01 (−0.04, 0.06) | |
| VPT | 0.01 (−0.01, 0.02) | 0.01 (−0.01, 0.02) | 0.01 (−0.002, 0.02) | 0.01 (−0.001, 0.02) | 0.01 (0.002, 0.03) | |
| Foot ulcer history | −0.05 (−0.29, 0.20) | −0.03 (−0.26, 0.21) | 0.04 (−0.20, 0.27) | 0.0001 (−0.23, 0.23) | ||
| DPN symptoms | ||||||
| Reduced feeling | −0.11 (−0.20, −0.01) | −0.08 (−0.18, 0.01) | −0.06 (−0.15, 0.04) | |||
| Pain | −0.16 (−0.31, −0.02) | −0.13 (−0.28, 0.02) | −0.01 (−0.17, 0.14) | |||
| Unsteadiness | −0.16 (−0.28, −0.04) | −0.13 (−0.25, −0.01) | −0.08 (−0.20, 0.05) | |||
| DPN-specific limitations in daily activities | −0.12 (−0.21, −0.04) | −0.08 (−0.18, 0.01) | ||||
| Emotional distress | ||||||
| Depressive Sx | −0.09 (−0.12, −0.05) | |||||
| DPN-emotional distress | −0.03 (−0.17, 0.12) | |||||
| Joint significance test | 3.4(2.6, 4.3) | 3.6(2.6, 4.5) | 3.6(2.6, 4.5) | 3.5(2.6, 4.5) | 3.6(2.7, 4.5) | 3.0(2.1, 3.9) |
CI, confidence interval; DPN, diabetic peripheral neuropathy; NDS, neuropathy disability score; VPT, vibration perception threshold.
Longitudinal analyses
The longitudinal regression model indicated that baseline predictors largely continued to show similar associations with self-rated health assessed at 18 months. As shown in Table 3 (model 7), the presence of cardiovascular disease (−0.36; 95% CI −0.58, −0.13) and higher depression symptom scores (−.07; 95% CI −0.11, −0.03) continued to show likely clinically meaningful associations with 18-month health ratings. Additionally, being in the UK (0.24; 95% CI 0.01, 0.48) and the presence of nephropathy (−0.33; 95% CI −0.62, −0.04) continued to show potentially meaningful independent associations with 18-month health ratings. Notably, unsteadiness (−0.19; 95% CI −0.32, −0.06) indicated a likely meaningful independent association, and DPN-specific limitations in daily activities scores (−0.12; 95% CI −0.22, −0.02) and higher neuroticism scores (−0.18; 95% CI −0.35, −0.003) indicated potentially clinically meaningful independent associations with lower 18-month health ratings, which were not observed in the fully adjusted baseline model.
Table 3.
Regression model predicting self-rated health at 18 months
| Variable | Model 7 Coefficient (95% CI) |
|---|---|
| Demo/Disease/Trait | |
| Country | 0.24 (0.01,0.48) |
| Female | −0.14 (−0.37, 0.10) |
| Type 2 diabetes | −0.22 (−0.49, 0.05) |
| Age | 0.01 (−0.001, 0.02) |
| Retinopathy | 0.03 (−0.19, 0.25) |
| Nephropathy | −0.33 (−0.62, −0.04) |
| Cardiovascular disease | −0.36 (−0.58, −0.13) |
| Comorbidities | −0.04 (−0.14, 0.06) |
| Neuroticism | −0.18 (−0.35, −0.003) |
| DPN severity | |
| NDS | −0.03 (−0.08, 0.02) |
| VPT | 0.01 (−0.01, 0.02) |
| Foot ulcer history | −0.07 (−0.32, 0.18) |
| DPN symptoms | |
| Reduced feeling | 0.06 (−0.04, 0.16) |
| Pain | 0.002 (−0.17, 0.17) |
| Unsteadiness | −0.19 (−0.32, −0.06) |
| DPN-specific limitations in daily activities | −0.12 (−0.22, −0.02) |
| Emotional distress | |
| Depressive Sx | −0.07 (−0.11, −0.03) |
| DPN-emotional distress | −0.04 (−0.12, 0.19) |
| Joint significance test | 3.5 (2.6, 4.5) |
CI, confidence interval; DPN, diabetic peripheral neuropathy; NDS, neuropathy disability score; VPT, vibration perception threshold.
Discussion
The goal of this study was to identify correlates of persons’ perceptions of their health, and assess these associations longitudinally, among a sample of people with DPN. Our findings supported our hypothesis that increased DPN severity is associated with lower self-rated health independent of demographic and other disease-related characteristics. However, research confirming the clinical significance of our findings is needed to more fully extend these and prior findings reported over 30 years ago [5] that linked DPN symptoms with lower self-rated health among people with diabetes. It is important to confirm these findings using clinical measures of DPN severity, as DPN symptoms do not consistently correlate with measures of DPN severity [22] and can differ in their relationships to outcomes [9]. Our results confirmed our expectation that the relationship between DPN severity and self-rated health would be attenuated by the addition of DPN symptoms, DPN-specific limitations in daily activities, and emotional distress variables. Baseline predictors largely continued to show effects of similar magnitude with 18-month health ratings, with unsteadiness and DPN-specific limitations in daily activities showing stronger associations with health ratings at 18 months compared to baseline.
This study also identified several demographic and disease-related characteristics as potentially and likely meaningful independent correlates of lower self-rated health among persons with DPN. This included living in the UK (compared with the USA), younger age, the presence of cardiovascular disease and nephropathy, and higher neuroticism. The potentially meaningful association between living in the UK compared with the USA and lower self-rated health scores, in addition to observed group differences (e.g. lower disease severity and higher functioning among individuals from the UK), may reflect that the UK sample included more people with type 1 diabetes, differences in recruitment, or ethnic, racial or cultural differences between the study sites. The independent association between younger age and lower self-rated health may reflect an earlier onset of DPN, although previous literature on the relationships between age, age of illness onset, and self-rated health show mixed findings [3,5]. Future work should continue to examine how these factors relate to self-rated health and health outcomes over time among individuals with DPN.
No substantive conclusions could be drawn regarding a meaningful independent relationship between having a history of diabetic foot ulceration and health ratings when adjusting for demographic factors, comorbid health conditions, and severity of DPN. A prior population-based study conducted in Norway reported an independent relationship between self-rated health and diabetic foot ulceration history when adjusting for demographic factors, comorbid health conditions, lifestyle variables, and illness-related variables such as insulin use, HbA1c, and diabetes duration [23]. The prior study differed from the current study in that the sample was comprised of individuals with diabetes, rather than individuals diagnosed with DPN, and did not control for severity of neuropathy. Additionally, a history of diabetic foot ulceration was assessed only via self-report in the prior study [23], whereas the current study supplemented self-reports with examination of medical records and podiatric assessment. Additional research is needed to reach a clearer answer on the independent association of diabetic foot ulceration and self-rated health among people with DPN.
Although we are not able to establish causality, our results show that physical symptoms, DPN-specific limitations in daily activities and more severe depression symptoms may represent mechanisms by which DPN severity contributes to reduced self-rated health. This is consistent with previous data showing that physical symptoms and functional status predict self-rated health among individuals with type 2 diabetes [24]. Heightened emotional distress has been posited as a pathway through which DPN symptoms like unsteadiness negatively impact self-rated health and QoL [25], and previous data from this cohort showed that DPN symptoms and limitations in daily activities were predictive of depression symptom severity cross-sectionally and over time [9,10]. The current findings are consistent with DPN-severity contributing to health ratings through increased symptoms, reduced functioning and increased depression symptoms. However, further work is needed to confirm the strength of these relationships and whether the steps of this potential pathway are causal.
The current study is limited in that it consists of two discrete (US and UK) samples of mostly men, and race and ethnicity were not assessed, which limit the generalizability of the findings. Further, causal inferences cannot be made from this study. Future studies with an experimental design that may manipulate correlates of self-rated health (e.g. reducing one’s level of unsteadiness, emotional distress) would allow for better assessment of the direction of influence underlying the observed associations between person and illness factors and self-rated health over time.
It is difficult to make specific clinical recommendations until DPN-related correlates of self-rated health are clarified further. It may be beneficial for clinicians to be more attentive to DPN symptom severity and particularly unsteadiness, as this symptom is often under-reported and underdiagnosed [13,22]. Recent work has shown that perceived DPN-related unsteadiness is closely associated with gait laboratory assessments of walking and balance impairment, suggesting individuals with DPN have a good sense of their level of impairment [26]. It may be beneficial to assess the impact of experienced symptoms on limitations in daily activities and emotional distress. Once identified, multifaceted interventions that target both biomechanical difficulties and emotional distress among people with DPN hold the potential to improve self-rated health as well as QoL [25]. Future research should test such integrative interventions and continue to model the myriad of aspects of health, well-being and expectations that come together to contribute to the important patient-reported outcome of self-rated health among individuals with DPN.
Inclusion of patient-reported outcomes such as self-rated health in DPN-related clinical care and research promotes a person-centred focus, and self-rated health may be particularly useful in that it consists of a single-item that can be easily incorporated into health services and research. Future research should examine whether perceptions of health predict important medical outcomes such as mortality in this population. This would contribute to our understanding of self-rated health as a risk factor for negative health outcomes as diabetes progresses and people develop complications. Additionally, further work is needed to better understand how self-rated health is distinct from, and maps onto, related patient-reported outcomes such as depression and QoL, and the importance of distinguishing health status from QoL has been reviewed [27,28]. The finding that self-rated health is linked to multiple important health indicators supports the growing interest in systematically assessing patient-reported outcomes as primary outcomes in diabetes research. Importantly, centring patient-reported outcomes like self-rated health in diabetes research and care aligns with American Diabetes Association’s recommendations for a person-centred approach to diabetes care [29].
What’s new?
Self-rated health is a robust independent predictor of morbidity and mortality in various populations, including persons with diabetes. However, the correlates of self-rated health among those with diabetes complications remain understudied.
Clinically assessed diabetic peripheral neuropathy (DPN) severity showed a potentially clinically meaningful association with lower health ratings, and this relationship appeared to be mediated by DPN-related symptoms, DPN-specific limitations in daily activities and depression symptoms.
The finding that self-ratings of health are independently linked to clinical indicators of nerve damage in the feet and psychosocial distress supports self-rated health as an important patient-reported outcome in diabetes research and care.
Acknowledgements
This study was supported by Diabetes UK (PI: Dr Vileikyte; RD00-0002009) and the American Diabetes Association (PI: Dr Rubin; 1-00-CR-11). This work is also supported by the Einstein-Mount Sinai Diabetes Research Center (P30 DK020541) and the New York Regional Center for Diabetes Translation Research (P30 DK111022). Dr Hoogendoorn is supported by the Drs David and Jane Willner Bloomgarden Family Fellowship Fund. Dr Gonzalez is also supported by NIH grants: R18 DK098742, R01 DK104845, R01DK121298, R01 DK121896.
Footnotes
Competing interests
None declared.
References
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