Unsheltered homeless and unstably housed adults have higher levels of stress and more health risk factors than sheltered homeless adults

ABSTRACT In the United States, approximately 580,000 individuals were homeless on a single night in 2020. Homelessness can be categorized into three subgroups: sheltered homeless, unsheltered homeless, and unstably housed. This study aimed to empirically examine whether homelessness subgroups were related to current stress, recent utilization of shelter-based mental health services, and current health risk factors. Data were collected at multiple homeless shelters in 2016 in the Oklahoma City area (N = 575). All participants completed assessments of demographic characteristics, including age, sex, race, marital status, years of education, and incarceration history and victimization. Multiple linear and logistic regression analyses were conducted. Results indicated that the sheltered group was younger and more likely to be White than the unsheltered group, had higher levels of education, and reported more lifetime months in jail than the unstably housed group. Unsheltered homeless and unstably housed adults used fewer shelter-based health services, exhibited more health risk factors, experienced greater levels of stress, and had higher levels of food insecurity than sheltered homeless adults. Homeless adults who reside at shelters benefit most from available shelter services. The development of policies and programs targeted toward increasing sheltering options for unsheltered and unstably housed adults is needed.


Background
People experiencing homelessness are among the most vulnerable members of society, and homelessness comes with important health implications. Previous studies have found that, compared with domiciled adults, people experiencing homelessness are more likely to experience chronic stress, food insecurity, sleep problems, mental health disorders, alcoholism, substance abuse, and injuries (Abdelrahman et al., 2018;Bakker et al., 2011;D'Amore et al., 2001;Midboe et al., 2019;Raven et al., 2017;Tsai & Rosenheck, 2013b). For instance, 43% of adults experiencing homelessness in the U.S. reported having a substance abuse disorder or other mental health problems, and an additional 23% reported both (Hwang et al., 2005). Homeless adults face significant barriers that limit their access to health care, which leads to increased health care costs and poorer health outcomes (Midboe et al., 2019). In fact, more than half of adults experiencing homelessness do not have health insurance in the United States (Kushel et al., 2001).
In 2020, the number of people experiencing homelessness on a single night in the United States was estimated to be 580,000 (Henry et al., 2021). Nearly two-thirds (61%) of homeless adults were sleeping in an emergency shelter, transitional housing, or supportive housing (sheltered homeless), and more than onethird (39%) were sleeping in a location not meant for human habitation such as a car, park, sidewalk, abandoned building, or on the street (unsheltered homeless) (Henry et al., 2021).
Few studies have examined the relations between homelessness subtypes (sheltered and/or unsheltered), shelter service utilization, and health behaviors. One study found that unsheltered women experiencing homelessness were more likely to use alcohol and drugs than domiciled women, had a higher risk of both poor mental and physical health, and were less likely to utilize available health services, including drug and alcohol abuse treatments (Nyamathi et al., 2000). Another study compared unsheltered and sheltered homeless adults in terms of their demographics and health service use. Findings indicated that unsheltered participants were less likely to have insurance and more likely to use emergency services and outpatient services than sheltered participants (Petrovich et al., 2020). Previous studies focused on this topic have had limitations. For instance, previous studies have focused on specific populations (e.g. unsheltered homeless only [Roundtree et al., 2019], Mexican girls [Castaños-Cervantes et al., 2018], women [Nyamathi et al., 2000], or veterans [Byrne et al., 2016]), did not examine health behaviors or health service utilization, or did not include unstably housed people (Byrne et al., 2016;Castaños-Cervantes et al., 2018;Nyamathi et al., 2000;Petrovich et al., 2020;Roundtree et al., 2019).
Unstably housed people are individuals who sleep overnight with family, friends, acquaintances, sex partners or at hotel/motel (Suchting et al., 2020). They were either included in the unsheltered group or omitted from previous homeless research. Thus, it is largely unknown whether unstably housed adults are different from sheltered and unsheltered homeless adults. Sheltered homeless, unsheltered homeless, and unstably housed adults may vary in terms of their shelter service utilization and health behaviors (Suchting et al., 2020). Further examination of this subject and subtypes of homelessness is needed to identify better ways to address health risk factors and improve health in this population.
Previous research has indicated that shelters which provide services to homeless adults can improve health outcomes, including reducing mental health problems, increasing health care use, reducing substance abuse, reducing daily stress, and improving healthy behaviors (Piepoli et al., 2016;White & Newman, 2015). However, some shelters have rules about who can stay there based on sex, arrest history, sexual violence, etc (Broadhead-Fearn & White, 2006). Thus, unsheltered homeless and unstably housed people who are not allowed to stay at shelters may have worse outcomes compared with sheltered homeless adults. Specifically, they may be less likely to utilize health care services, and this may have detrimental effects on their health behaviors and health outcomes (Suchting et al., 2020). To do so, this study focused on risk and/or protective factors that have an impact on modifiable health behavior changes (i.e. current stress, recent utilization of shelter-based mental health services, and current health risk factors), which are thus targetable for intervention.
The purpose of this study is to empirically examine whether shelter status the previous night (sheltered vs. unsheltered vs. unstably housed) was related to current stress, recent utilization of shelter-based mental health services, and current health risk factors provide services to homeless adults can improve health outcomes, including reducing mental health problems, increasing health care use, reducing substance abuse, reducing daily stress, and improving healthy behaviors (Piepoli et al., 2016;White & Newman, 2015).
It is hypothesized that: unsheltered homeless and unstably housed adults will exhibit lower use of shelter-based mental health services, higher levels of stress, and more health risk factors than sheltered homeless adults.

Participants and procedure
Data were collected at six homeless shelters between July and August 2016 in the Oklahoma City area. Most of the shelters provided overnight shelter (n = 5) and other services to homeless adults. One shelter (i.e. the Homeless Alliance City Care Day Shelter) only provided daytime services including food, legal aid, mental health counseling, and substance abuse counseling. All of the shelters offered services (e.g. food, substance abuse counseling) to adults experiencing homelessness. Homeless individuals were eligible to participate in this study if they met the following criteria: (1) earned a score ≥4 on the Rapid Estimate of Adult Literacy in Medicine-Short Form (REALM-SF [Arozullah et al., 2007]) indicating >6th grade English literacy level, (2) were ≥18 years of age, and (3) were receiving services at the targeted shelters.
Flyers advertising for this study and sign-up times were posted around shelter campuses. Individuals who were interested in the study were given a screening appointment, and they received detailed information about the study during that appointment. Those who remained interested in participating were screened for study inclusion. Those who qualified for the study completed a tablet-based 1.5-hour survey. Participants who completed the assessments received a $20 gift card as compensation. The study procedure was approved by the Institutional Review Board at the University of Oklahoma Health Sciences Center. Details of the study design are described elsewhere (Daundasekara et al., 2019;Gonzalez et al., 2018;Vijayaraghavan et al., 2019).

Demographics
All participants completed assessments of demographic characteristics, including age, sex, race, marital status, and years of education.

Three homelessness subgroups
Participants were asked, "Where did you sleep last night?" Based on their response, participants were divided into three categories: (Midboe et al., 2019;Turnham et al., 2006) (1) sheltered homeless (homeless shelter and/or drug or alcohol treatment center), (2) unsheltered homeless (outside or on the street), and (3) unstably housed (friend's or family member's house or apartment, hotel or motel, other temporary location).

Incarceration history and victimization
Incarceration history was assessed using two items, "Have you been incarcerated (jail or prison) in the past year?," and response options were yes (1) or no (0). Participants were also asked, "During your lifetime, how much time have you spent in jail or prison?," and the responses were calculated in months.

Shelter-based service utilization
Shelter-based utilization of mental health services was assessed via four questions, "Over the past 3 months, have you received Mental Health/Behavioral Health Counseling at local shelters?," "Over the past 3 months, have you received Substance Abuse Counseling at local shelters?," "Over the past 3 months, have you received any meals at local shelters?," and "Over the past 3 months, have you met a case manager at local shelters?," and response options were yes (1) or no (0).

Health risk factors
Physical activity in the past week, sleep, binge drinking in the past month, drug use yesterday, and obesity were assessed. Physical activity was assessed using two items to determine whether, in a usual week, participants participated in moderate-intensity physical activities such as brisk walking, bicycling, vacuuming, or gardening, and/or vigorous-intensity physical activities such as running, aerobics, or heavy yard work. Respondents who indicated that they did moderate-or vigorous-intensity physical activity were also asked to report how many days per week they spent at least 10 minutes at a time doing the activities, and how much total time (in minutes) per day they spent doing the activities. After vigorous minutes were multiplied by 2, total physical activity minutes were multiplied by the number of days per week to refer to participants' total minutes spent in moderate-to-vigorous physical activity (MVPA) in the past week (Centers for Disease Control and Prevention, 2006). Sleep deprivation was measured by the responses (yes or no) to the question, "I do not get enough sleep." Binge drinking status was assessed by asking a question, "How often in the past 30 days have you consumed [5 for men/ 4 for women] or more standard drinks? (Dietary Guidelines for Americans Committee, 2015)" The responses were dichotomized as "binge drinking in the past 30 days" vs. "no binge drinking in the past 30 days." Drug use was assessed by asking one question, "Please select all the substances that you used yesterday (check all that apply)." Answers were dichotomized into any drug use yesterday (e.g. Cannabis, Cocaine, K2, and Amphetamine) and no drug use yesterday. BMI was calculated based on weight and height, and participants were categorized into underweight or normal (0), and overweight or obese (1) (Centers for Disease Control and Prevention, 2015).

Stressors
Level of life stress was assessed using the Urban Life Stress Scale, which is a 21-item self-report checklist of potential sources of chronic stress (Jaffee et al., 2005). The degree of stress experienced related to each item was rated on a 5-point scale, from 1, "no stress at all," to 5 "extremely stressfulmore than I can handle." The USDA Food Security Survey (Bickel et al., 2000) was used to measure food insecurity during the last 12 months. This measure consists of 5 items (e.g. in the last 12 months, you could not afford to eat balanced meals) scored from 0 to 6.

Statistical analyses
Comparisons between three homeless subgroups (i.e. sheltered homeless vs. unsheltered homeless vs. unstably housed) were made using Chi-square tests for categorical variables (e.g. race) or one way ANOVA for continuous variables (e.g. age) with Fisher's Least Significant Difference post-hoc test, as appropriate. The main predictor was the category of three homeless subgroups, and outcomes were shelter-based service utilization, stress measures, and the presence of specific health risk factors. Multiple linear regression was used to examine the relations between homeless subgroups and continuous outcomes (e.g. the Urban Life Stress Scale), and logistic regression was used for binary outcomes (e.g. binge drinking last month: yes or no) adjusting for covariates (i.e. age, sex, years of education, and race). All analyses were performed using SPSS version 25. Table 1 presents frequencies and percentages for all variables and differences between the three homelessness subgroups.

Sociodemographic characteristics
Analyses indicated that the sheltered group was younger and more likely to be White than the unsheltered group (42.64 vs. 47.42; 60.8% vs. 50.9%, respectively). In addition, sheltered homeless had higher levels of education than the unstably housed group (12.07 vs. 11.31) (see Table 1).

Incarceration history
Results indicated that unsheltered homeless and unstably housed groups reported more lifetime months in jail compared with the sheltered homeless group (49.32 and 56.68 vs. 24.56). Also, unsheltered homeless were more likely to report incarceration in the past year compared with unstably housed individuals (45.8% vs. 23.6%) (see Table 1).
Comparison of use of shelter-based healthcare services, health risk factors, and stressors as a function of state of homelessness Shelter-based service utilization A higher proportion of sheltered homeless reported receiving mental health/behavioral health counseling (30.7% vs. 15.3% and 9.1%, respectively), substance abuse counseling (27.2% vs. 5.1% and 5.5%, respectively), and meeting a case manager in the past 90 days (78.6% vs. 39.0% and 36.4%, respectively) than unsheltered homeless and unstably housed adults (see Table 2). The proportion who received meals at shelters was not different (p<.05) between the three subgroups (see Table 2). Similar results were found after controlling for covariates (see Table 2).

Health risk factors
Sheltered adults reported lower total minutes of MVPA per week than unsheltered adults (337.45 vs. 595.64). Unsheltered adults reported the highest binge drinking, followed by unstably housed and sheltered homeless (20.8% vs. 65.8% vs. 40.0%, respectively). Sheltered adults reported less drug use yesterday compared with unsheltered adults and unstably housed adults (4.7% vs. 29.4% and 34.5%, respectively). Sheltered adults were less likely to report they do not get enough sleep compared with unsheltered and unstably housed adults (30.7% vs. 15.3% and 9.1%, respectively). Sheltered homeless adults were more overweight or obese than unsheltered homeless (68.6% vs. 50.4%). Similar results were found after controlling for covariates (see Table 2).

Stressors
Daily stress, as measured by the Urban Life Stress Scale, and food insecurity were lower for sheltered homeless compared with unsheltered homeless (47.93 vs. 51.63; 3.54 vs. 4.59, respectively). After controlling for covariates, results indicated that unsheltered homeless adults reported higher levels of daily life stress than sheltered homeless adults (b = 4.18, p = 0.009) and both unsheltered adults and unstably housed adults were more likely than sheltered adults to report food insecurity (b = 1.14, p < 0.001; b = 0.75, p = 0.020, respectively).

Discussion
The primary purpose of this study was to examine whether shelter status the previous night was related to measures of stress, recent utilization of shelterbased services, and current health risk factors. Consistent with our hypotheses, sheltered homeless adults used more shelter-based mental health services, had fewer health risk factors, and reported lower levels of stress than unsheltered homeless adults and unstably housed adults. That is, unsheltered homeless adults were more likely to report not getting enough sleep, binge drinking, using illicit drugs, and experiencing higher levels of daily stress and food insecurity than sheltered homeless adults. Similarly, unstably housed adults were more likely to report inadequate levels of sleep, binge drink, use illicit drugs, and experience a higher level of food insecurity than sheltered homeless adults.
Our findings are consistent with previous research, indicating that: white adults are more likely to be sheltered than non-white adults, homeless adults who receive shelter-based mental health services may demonstrate better mental health, fewer substance abuse problems, and healthier behaviors (Piepoli et al., 2016;White & Newman, 2015). Sheltered homeless adults may have more access to health care services, and in turn, demonstrate fewer health risk factors and lower levels of stress than unsheltered or unstably housed adults.
To our knowledge, this study is the first to examine racial inequalities and levels of physical activity and  -1.14 (0.24) <.001 0.75 (0.33) 0.02 Note: N = Sample size, M = Mean, SD = Standard Deviation, Data displayed in the unadjusted column are based on 570-575 subjects, depending on the variable, due to missing data, B = Beta, SE = Standard Error, 1 Chi-square tests for categorical variables (sex, race, and incarcerated in jail in the past year) or one way ANOVA for continuous variables (age, years of education, and months in jail lifetime) with Fisher's Least Significant Difference post-hoc test, Means with differing subscripts are significantly different at the p < .05 level. 2 All models adjusted for age, years of education, sex, and race. 3 The level of life stress was assessed through the Urban Life Stress Scale, which is a 21item self-report checklist of potential sources of chronic stress. 4 The USDA Food Security Survey was used to measure participants' food insecurity during the last 12 months.
rates of overweight/obesity among the three homeless subgroups. Most minority groups (e.g. African Americans) experience homelessness at higher rates than Whites in the United States (HUD Exchange, 2020). However, our results demonstrate that Whites experiencing homelessness are more likely to be sheltered than non-white adults, in turn, they are more likely to receive the benefits of shelter-based services. It is known that insufficient physical activity is common in homeless populations in general (Tsai & Rosenheck, 2013a). Moreover, it has been reported that the rates of overweight and obesity among homeless adults are high and increasing (Martins et al., 2015;Tsai & Rosenheck, 2013a, 2013b. The findings from the current study indicated that sheltered homeless adults are more likely to be sedentary and overweight or obese than unsheltered homeless adults. However, higher physical activity and lower overweight/obesity rates for unsheltered homeless and unstably housed adults do not necessarily mean that they are healthier than sheltered homeless adults. It may be the case that sheltered homeless adults are more likely to have physical disabilities limiting physical activity, resulting in lower levels of exercise and higher rates of overweight/obesity. Further, unsheltered homeless adults may have lower rates of overweight/obesity and greater levels of physical activity because they eat fewer meals and have to travel from place to place to get their basic needs met (e.g. traveling to various shelters to acquire food). Although there is an increasing number of studies that focus on physical activity and obesity among sheltered homeless adults (Kendzor et al., 2017;Koh et al., 2012;Martins et al., 2015;Tsai & Rosenheck, 2013a), we found none that have similarly targeted unsheltered and unstably housing adults.
Interventions that target physical activity and overweight/obesity among unsheltered homeless adults are needed. Findings from this study also indicate that the heterogeneity of this population should be considered when developing policies and intervention tools to address the health care needs of adults experiencing homelessness. Unsheltered homeless and unstably housed adults appeared to have greater unmet needs than sheltered homeless adults, yet they received fewer services at shelters. That is, unsheltered homeless and unstably housed people may be less likely to utilize health care services, and this may have detrimental effects on their health behaviors and health outcomes (Suchting et al., 2020).
This finding is consistent with previous research indicating that unsheltered homeless adults have greater needs for care and experience longer periods of lifetime homelessness (Nyamathi et al., 2000). Furthermore, current study findings showed that unsheltered homeless and unstably housed adults reported longer periods of lifetime incarceration than sheltered homeless adults, and unsheltered homeless adults were more likely to report incarceration in the past year than unstably housed adults. This finding is important because many shelters have rules about who can stay there based on sex, arrest history, sexual violence, etc (Broadhead-Fearn & White, 2006). Thus, many unsheltered homeless or unstably housed adults may not have access to the drop-in services that are available to shelter residents due to their incarceration history (Nyamathi et al., 2000). Barriers that reduce access to care for unsheltered homeless and unstably housed groups should be considered when developing and implementing policies and intervention tools for this marginalized and underserved population.
This study has several limitations. First, we did not assess duration of sheltered status. The three homeless subgroups (sheltered homeless, unsheltered homeless, and unstably housed) were categorized based on participants' whereabouts the previous night. This definition was based on the U.S. Department of Housing and Urban Development's point-in-time method for counting sheltered homeless persons, which is utilized to avoid duplicated estimates of homeless persons in sheltered and unsheltered locations (23). Future longitudinal research should measure the duration of current sheltering status to examine how the duration of sheltered status (e.g. number of nights at the shelter in the previous month) relates to the utilization of shelter-based mental health services, stress, health risk factors, and continued homelessness. Second, unsheltered homeless and unstably housed subgroups may have been underrepresented in this study because the study data were only collected at shelters. Third, the data were collected from adults who homelessness in one city, and the findings may not be generalizable to homeless populations in other U.S. cities, or states. However, this study surveyed a large sample of adults experiencing homelessness, representing a range of races as well as other demographic characteristics from an understudied region of the U.S. When this study was conducted in 2016, there were 1368 homeless people on a single night in Oklahoma City, meaning that roughly 42% of this population were included in the study sample (He et al., 2016). Other study limitations include cross-sectional data collection and health service use, health behaviors, and stressors were self-reported. Thus, participants may have under-or over-reported information, and this may have biased the study findings.

Conclusions
Despite these limitations, findings from this study have notable implications for health research in this understudied population. To best of our knowledge, this is one of the first studies to compare how these homeless subgroups based on where they reside previous night vary in terms of health risk factors, current stress, and shelter-based health service use. Our findings are important as they indicate that unsheltered homeless and unstably housed subpopulations may be more vulnerable and experience greater needs than sheltered homeless adults. Specifically, unsheltered homeless and unstably housed adults are more likely to exhibit lower use of shelter-based health services, higher levels of stress, and more health risk factors than sheltered homeless adults. Homeless shelters play an important role in providing for the basic needs and improving the health of adults experiencing homelessness. Findings from the current study may inform the development of policies and programs that are targeted toward homelessness subgroups.
Additional research is needed to identify barriers to shelter utilization for unstably housed and unsheltered adults experiencing homelessness to inform health promotion and health intervention programs for this understudied and underserved population. Addressing these barriers may improve the health of homeless adults, reduce the duration of homeless bouts, and may ultimately reduce overall homelessness in the U.S.