In this meta-analysis, we found a statistically significant relationship between worse GSRH and an increased risk of death. Study participants' responses to a simple, single-item GSRH question maintained a strong association with mortality even after adjustment for key covariates such as functional status, depression, and co-morbidity. Additionally, this relationship persisted in studies with a long duration of follow-up, for men and women, and irrespective of country origin.
Previous narrative reviews by Idler and Benyamini1
, Thomas et al.,16
presented the study results of GSRH and mortality with the majority of studies demonstrating a significant association. Despite the value of these previous reviews, neither involved a systematic or quantitative review of previously published reports. The meta-analytic techniques employed allowed us not only to estimate an overall relative risk of mortality for individuals with “poor” health, but also to assess the relative risk in subgroups and address the robustness of this relationship after adjustment for variables known to influence self-rated health and mortality.
In this study, we were able to assess whether a single-item GSRH question adds incremental value to the objective health measures currently collected and identified on surveys and in clinical practice. We found the association between GSRH and mortality was reduced among studies that adjusted for co-morbid illness, particularly among the subgroup of persons reporting “poor” health. This is not surprising as individuals with worse health are more likely to have multiple co-morbid conditions and when rating their health consider these existing medical problems. However, in a sensitivity analysis limited to studies that adjusted for co-morbid illness, a graded relationship was present with persons reporting “poor” health having a 1.74 [1.51, 2.02] times higher risk of dying than their counterparts reporting “excellent” health. Additionally, a significant, graded relationship of higher relative risks of mortality at worse GSRH persisted even when excluding studies that did not control for important domains known to influence self-rated health including depression, cognitive function, functional status, and socioeconomic status. This confirms prior evaluations of the relationship between GSRH and mortality that indicate the GSRH represents a broader dimension of health than these domains.33,34
Some of the more widely used tools from prior research in this area have focused on geriatric populations and have demonstrated predictive validity. A prediction tool developed by the ACOVE project was designed to identify elders at risk of death in the ensuing year.35
In the current meta-analysis, we have demonstrated that an array of prediction models that include GSRH employed in community-based studies also predicts subsequent mortality. We included studies in our analysis that evaluated the relationship in all adults, irrespective of age. Based upon the results of this meta-analysis, the GSRH measure demonstrates strong predictive properties in both geriatric and nongeriatric populations.
The observed association between GSRH and mortality may occur because GSRH serves as a proxy for the array of important covariates known to predict health and resource needs.14,36–38
GSRH may also function as a dynamic evaluation reflecting judgments about trajectory of health, rather than just the current level of health.39
It has also been postulated that GSRH influences subsequent health behaviors40
that affect health status, such as lifestyle modifications, or that it reflects an individual's personal knowledge of existing or future events that may attenuate decline in health.15,34
Importantly, GSRH appears to provide summative information about the various domains of health, as viewed by the individual responding to the question. Additionally, GSRH measures seem to capture some aspects of health that cannot easily be measured, as indicated by the persistent relationship between GSRH and mortality, even when multiple, important domains of health are controlled for in multivariate analyses.20,26
This meta-analysis provides additional evidence supporting the value of incorporating a single-item measure of self-rated health into risk assessment tools. The single-item GSRH measure takes seconds to collect and can be captured routinely and with a low burden of collection. Such a question could easily be collected from large populations and is readily interpretable, requiring no special scoring. In concert with other important predictors of health outcomes such as age, it would provide a straightforward, patient-centered, and inexpensive method to identify persons at increased risk of mortality. In the clinical environment, this information could be useful risk-stratifying individuals and triaging those with worse self-rated health to more intensive evaluations and care management programs.
The current manuscript was not designed to assess the ability of GSRH used in isolation as a risk prediction tool. Further research will aid in understanding the relative contribution and potential drawbacks of single-item measures of general health to risk prediction in the clinic setting. For example, to be useful in risk assessment, tools need strong performance characteristics, particularly for discriminating between persons at risk and not at risk.41
In a previous study, we evaluated the performance characteristics of GSRH in a clinic-based veteran population compared with the Physical Component Score (PCS) of the Short Form 36 and to a validated co-morbidity score.42
We also assessed the relative contribution of GSRH to age alone as a risk prediction tool, and to the co-morbidity score. The discriminatory ability, as measured by the area under the receiver operator curve (AUC/c-statistic), was 0.74, comparable with the performance of the PCS in our study (AUC/c-statistic 0.73) and significantly better than age alone (AUC/c-statistic 0.65).43
By comparison, the widely used VES-13, which includes GSRH, age, plus 11-items measuring functional status, has a reported AUC/c-statistic of 0.78.35
One of the possible practical limitations of using self-rated health measures as risk prediction is the potential for patients to report poorer health than they actually may experience in order to become eligible for more healthcare resources. Alternatively, providers may encourage their patients to report worse health to skew the profile of their patient population for future risk adjustment. Such problems exist for all tools employed in risk prediction and adjustment, whether these tools use self-reported health measures or administrative data.41
There are potential limitations to our study. First, exclusion of non-English language articles may have missed eligible studies, although language limitation does not always introduce bias into systematic reviews.44
Second, the quality of our study is dependent upon the quality of the original publications included in our analysis. However, we used strict criteria to enhance the quality of the studies included in our meta-analysis. Third, all systematic reviews are subject to publication bias from the general lack of reporting on negative associations. However, we did not detect publication bias. Fourth, there was variability in the number and definition of covariates controlled for across studies. To address this issue, we used strict inclusion criteria for the studies and performed sensitivity analyses. The consistency of the point estimate for mortality prediction in the sensitivity and subgroup analyses supports the concept that the relationship between GSRH and subsequent mortality is robust.
In summary, worse GSRH maintains a strong association with an increased risk of mortality even after accounting for key covariates such as co-morbidity. Although many issues related to the optimization of using a single-item GSRH need to be resolved, it appears to be a powerful adjunct that may help identify at-risk individuals and illuminate underlying illnesses that may go otherwise undetected during routine evaluations. We envision the current study as the first step towards familiarizing clinicians and health planners with the concept of assessing GSRH. Further work is needed to determine if assessing patients' GSRH in routine clinical settings can be used to improve care through the identification of groups at risk for increased mortality and other important health outcomes. Nonetheless, given the ease of use and low burden of using a single-item GSRH, the routine collection of these data may offer a beneficial tool in health care planning.