This study evaluated the impact of two dimensions of access—geographic accessibility and services availability—on treatment retention among patients diagnosed with schizophrenia or bipolar disorder. These dimensions have parallels in two maxims of health system planning: Jarvis's Law of Distance and Roemer's Law (Jarvis 1850
; Roemer 1961
). In 1850, Jarvis described a distance–decay relationship whereby the likelihood of utilization diminishes at greater distances from providers. A century later, Roemer showed a positive association between hospital bed supply and bed days per 1,000 people in a community. Both “laws” suggest substantial unmet need for care, as indicated by greater utilization when accessibility and availability increase. The associations of geographic accessibility and services availability with continuity of care have received little research attention. Using national longitudinal data, we evaluated their impact on long-term VA health system and mental health services retention.
By the end of FY98, 12-month gaps in VA service use were observed among 21.0 percent of patients with SMI. We observed gaps in mental health services use among 41.7 percent of patients. The generally continuous nature of utilization among patients with SMI is consistent with findings from previous studies (Ronis et al. 1996
Study findings provide evidence that geographic accessibility and services availability influence long-term continuity of care. However, the observed effects were small. For overall VA health system retention, the hazard ratio associated with a 5-mile increase in distance to nearest VA service site was 1.010. For VA mental health services retention, the hazard ratio associated with living 5 miles farther from psychiatric services was 1.011. In sensitivity analyses, noted above, hazard ratios for individuals living at least 25 miles from the nearest relevant provider were 1.082 and 1.170 for VA health system and for mental health services retention, respectively. Greater VA inpatient bed availability was associated with increased health system retention.
These results are consistent with those of previous studies examining geographic accessibility and the timeliness of care for psychiatric patients over shorter periods. Greater distance from providers has been associated with lower likelihood of receiving outpatient visits following discharge, and less continuous psychiatric and nonpsychiatric utilization (Druss and Rosenheck 1997
; McCarthy 2002
). Our findings regarding the impact of VA inpatient bed availability on health system retention are consistent with those of previous studies of availability effects on services utilization (Roemer 1961
; Kekki 1980
; Bindman, Keane, and Lurie 1990
In assessing the small magnitude of the observed accessibility and availability effects, compared with those observed in previous studies, several factors should be considered. First, the factors influencing delayed care may be distinct from those affecting loss-to-care. The present study examined long-term gaps in health system and mental health services utilization between last use of FY98 and the end of FY02. For patients with SMI, 12-month gaps may represent loss to care, whereas briefer gaps may represent delayed care.
Second, the relative influence of access barriers may diminish as need increases. Although it was not feasible to include time-varying measures of need for care, need may increase during longer intervals without care. For patients with SMI, guidelines recommend no fewer than three outpatient contacts per year, in order to reduce risks of mental health exacerbations. After longer periods without care, patients may be more motivated to overcome access barriers.
There may also be selection factors affecting which individuals seek any VA care, and thus were eligible for inclusion in this study. Among all eligible veterans, those living further from VA providers and who also seek VA care may have greater unmeasured need for services (and willingness to surmount access barriers) than veterans living in areas with greater access and who become VA patients.
Finally, there may be greater measurement error in longitudinal models predicting long-term gaps in utilization, as compared with assessments over a briefer time period. For example, baseline characteristics—particularly of need for care—may change substantially over time. It is unclear to what extent health system accessibility and availability may have changed during the observation period. In a 1-year period, 15 percent of patients with SMI may change zip codes of residence, with a median travel distance of 13 mile (McCarthy 2002
), and patients may be more likely to move closer to VA treatment facilities. Further research is also needed to evaluate our assumption that prolonged periods without health system utilization have clinical importance, separate from their considerable lack of concordance with treatment guidelines.
This study had several limitations. First, this study did not include measures of non-VA health services utilization. As a result, we cannot determine the extent to which patients who have a 12-month gap in VA services received no services at all, or instead received services from non-VA providers. We acknowledge that this is a concern, however we expect that cross-system use among VA users with schizophrenia and bipolar disorder is relatively low (Desai, Rosenheck, and Rothbard 2001
; Desai and Rosenheck 2002
). More than half of all study patients had service-connected disabilities. Finally, there is conflicting evidence as to whether VA patients living in remote areas are more likely to receive non-VA care (Borowsky and Cowper 1999
; Desai and Rosenheck 2002
Second, it was limited to predominantly male veterans who received care in the VA health system. One may question the generalizability of these findings to veterans and nonveterans receiving care in other settings. However, veterans and nonveterans may be similar in their utilization patterns after controlling for patient predisposing, enabling, and need characteristics (Wolinsky et al. 1985
). Moreover, comparisons of VA and non-VA patients with schizophrenia suggest that, although VA patients are older and have higher incomes, they do not differ in terms of clinical status, satisfaction with providers, or community adjustment (Rosenheck et al. 2000
Third, although we censor patients at their observed dates of death, the BIRLS data may be less sensitive for patients who are not service connected and who receive only outpatient treatment (Dominitz, Maynard, and Boyko 2001
). As a result, analyses may overestimate the risk of having a prolonged gap in health system contacts among these patients. However, given the high level of service-connection and rates of hospitalization among VA patients with SMI (Blow et al. 2003
), this may not significantly influence study results. Further, although straight-line distance provides a reasonable proxy for travel time (Phibbs and Luft 1995
), there may be systematic differences in travel resources between study subjects living at different distances from VA providers.
Health system and mental health services retention, as defined in this study, provide measures of some but certainly not all of the key conceptual dimensions of continuity that have been described in the literature. Retention in care provides a broad indicator of global continuity as “an uninterrupted succession of events” consistent with patient care needs across illness episodes (Shortell 1976
). This application is appropriate in studying services utilization by patients with SMI, given their substantial needs for ongoing contacts. However, it is unclear to what extent it may be applied to patient subpopulations with more episodic health services needs.
As discussed by Shortell 30 years ago (Shortell 1976
), the interrelationships of continuity of care and access to care remain poorly understood. This study examined whether, among patients with SMI, health system geographic accessibility and services availability influenced long-term gaps in health system and mental health services utilization. Geographic accessibility barriers were associated with increased risks of long-term gaps in health system and mental health services utilization, particularly for individuals living at least 25 miles from providers. VA services availability was also associated with VA health system retention.
Consistent with prior research, patient predisposing (i.e., age, gender, race/ethnicity, marital status, service connection, and homelessness) and need factors (i.e., medical morbidity, primary psychiatric diagnosis, inpatient admission in FY98) were substantial predictors of utilization. To improve continuity of care for patients with SMI, health system clinicians and policy makers should also focus efforts on patient-level factors associated with long-term loss to care. Further research regarding patient and treatment factors associated with these gaps in utilization may inform these efforts.
For patients with schizophrenia and bipolar disorder, accessibility and availability barriers are associated with long-term disruptions in needed services contacts. Over the past decade, the VA has improved access by expanding the number of health system contact points and has worked to ensure adequate inpatient resources in areas with high concentrations of veterans. The present study underscores the importance of these efforts.