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AIDS drug treatment program
Health & Place 6 (2000) 33±40
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Determinants of geographic mobility among participants in a population-based HIV/AIDS drug treatment program Evan Wood a, Benita Yip a, Nada Gataric a, Julio S.G. Montaner a, b, Michael V. O'Shaughnessy a, c, Martin T. Schechter a, d, Robert S. Hogg a, d,* a
British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada b Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Colombia, Canada c Department of Pathology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada d Health Care and Epidemiology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
Abstract This study was undertaken to determine the geographic distribution and patterns of migration of persons with HIV in British Columbia. Our analysis was restricted to all HIV-positive men and women aged 18 years and over who had completed a participant survey and were enrolled in the HIV/AIDS Drug Treatment Program between September 1992 and September 1997. Patterns of migration were determined by examining participants whose postal code changed between July 1995 and September 1997. Statistical analysis were carried out using both parametric and non-parametric methodologies. Stepwise logistic regression was used to determine baseline predictors of migration. The ®nal multivariate model revealed that residing in a census subdivision with a population less than 100,000, being heterosexual, acquiring HIV through intravenous drug use, and the absence of AIDS at baseline were all independently associated with moving census subdivisions during the period of observation. In summary, our analyses demonstrate the need for the continued study of the evolving geography and migration patterns of persons with HIV. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: HIV; AIDS; Migration; Canada; British Columbia; Antiretroviral therapy; Population based cohort
1. Introduction Previous studies of migration and HIV/AIDS in North America have shown considerable mobility among persons with HIV (Cohn et al., 1994; Davis and Stapleton, 1991; Ellis and Muschkin, 1996; Vergh-
* Corresponding author. Tel.: +1 (604) 631-5516; fax: +1 (604) 631-5464. E-mail address: [email protected] (R.S. Hogg).
ese et al., 1989; Rumley et al., 1991). Researchers have characterized patterns of rural to urban and urban to rural migration, and identi®ed motivating factors such as the need for social services, family support, and specialized health care (Ellis and Muschkin, 1996; Tatum and Schoech, 1992; Davis and Stapleton, 1991; Fordyce et al., 1997; Rumley et al., 1991). Analysis of the migration of persons with HIV has several implications. Of foremost importance is determining where people with HIV and AIDS are choosing to reside at dierent stages of their illness so that
1353-8292/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 3 - 8 2 9 2 ( 9 9 ) 0 0 0 2 8 - 3
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E. Wood et al. / Health & Place 6 (2000) 33±40
health care resources are most appropriately allocated. Similarly, recognizing the evolving geography of HIV is important so that HIV/AIDS education and prevention strategies are directed as eciently and eectively as possible. Various studies have contributed to understanding the distribution and spread of HIV/AIDS by mapping the origin of the HIV virus and its diusion over space (Gould, 1993; Shannon et al., 1990, Smallman-Raynor et al., 1992). This work has determined that HIV/ AIDS has tended to cluster in certain areas of the urban landscape and among certain population subgroups such as homosexuals and intravenous drug users (Shannon et al., 1991; Gould, 1993). It has been suggested, however, that as the epidemic evolves and diuses, considerable overlap can be expected between these dierent sub-groups, and a growing number of new HIV infections among persons not traditionally at risk (Strathdee et al., 1994). Analysis of the migration of persons with HIV is one of the best ways to anticipate how the epidemic will evolve, and to direct the necessary steps to try and avoid further spread. In Canada, analysis of the geographic distribution and patterns of migration of persons with HIV/AIDS has revealed that the majority of HIV+ individuals reside in the large metropolitan cities and that the overall rate of inter-provincial migration by persons with HIV is comparable to that of the general Canadian population (Hogg et al., 1996, 1997). These studies linked data on the place of AIDS diagnosis to death registration systems and were restricted to looking at inter-provincial migration. As a result, analysis has been lacking on the geographic distribution and migration patterns of persons with HIV within provinces. This study was undertaken to determine the geographic distribution and patterns of migration of persons with HIV in British Columbia. Speci®cally, we sought to determine where in the province persons with HIV are living, the rate of migration within this population, and where individuals who are migrating are moving to and from. In addition, we have investigated some of the social and health-related factors associated with individuals' decisions to migrate.
2. Methods In British Columbia anti-HIV drugs have been centrally distributed at no cost to eligible HIV-infected individuals since 1986. In October 1992, the HIV/AIDS Drug Treatment Program became the responsibility of the British Columbia Centre for Excellence in HIV/ AIDS (the Centre) which is located in downtown Vancouver. From 1986 to 1998, a total of 5005 HIV-posi-
tive British Columbians received anti-HIV therapy. Of these, 4171 have been enrolled in the Drug Treatment Program and 2384 are currently receiving anti-HIV therapy. The current criteria for treatment eligibility is based on a documented HIV infection and a CD4 cell count consistently below 500 cells/mm3 or a plasma viral load determination greater than 5000 copies/ml (British Columbia Centre for Excellence in HIV/AIDS, 1995). Participants meeting these criteria are enrolled in the program by their general practitioner on submission of a prescription for antiretroviral or approved antimicrobial medications. The Centre's Drug Treatment Program remains the only free source of antiretroviral medications in the province. Physicians enrolling an HIV-positive individual into the Centre's Drug Treatment Program must complete a drug request enrollment form. The enrollment form acts as a legal prescription and compiles information on the HIV-positive applicant's address and enrolling physician, past HIV-speci®c drug history, CD4 cell counts, and current drug requests. Each request is reviewed by a quali®ed practitioner to ensure that it meets the Centre's established therapeutic guidelines. Approved prescriptions are renewed every 2 months. At the time of the initial re®ll each participant is asked to complete an enrollment survey and program consent form, while their physician is asked to complete a clinical staging form. Participant surveys and clinical staging forms are completed annually. The participant survey elicits information about the participant's socioeconomic status, social support, clinical status, and current and previous use of HIV-related medications and complementary therapies. Data from the surveys were used to create sociodemographic pro®les of the participants that quali®ed for the study. Our analysis was restricted to all HIV-positive men and women aged 18 years and over, who had completed a participant survey, and were enrolled into the program between September 1992 and September 1997. As postal code histories have only been maintained since July 1995, we restricted our analysis to those participants that started or were still on antiHIV medication after that date. The primary endpoint in this analysis was a change in Census Subdivision. Patterns of migration were determined by examining participants whose postal code changed between July 1995 and September 1997. Census subdivision (CSD) is the term used by Statistics Canada to de®ne municipalities or geographic areas that have been created as equivalents of municipalities for the dissemination of statistical data. As we were not interested in movements within the same municipality, only those participants whose postal code changes re¯ected a movement to a new census subdivision quali®ed as migrants in this analysis. Movements between CSDs were determined by linking
E. Wood et al. / Health & Place 6 (2000) 33±40
each participant's postal code or codes to CSDs using Statistics Canada's Postal Code Conversion File (P.C.C.F.). This ®le generated a CSD geographic code for the CSD with which each participant's current and previous postal codes are associated. Once this linking was performed, ArcView Geographical Information System (GIS) software was used to map the geographic distribution and migration patterns of the participants based on their current and previous CSD codes (Environmental Systems Research Institute, 1996). A digital cartographic ®le of British Columbia with the boundaries of all CSDs was entered into the GIS. This ®le contained a digital map of the province with all Census Subdivision boundaries overlaid and an attribute information table which contained the CSD geographic codes for each of the 713 Census Subdivisions in the province. Similarly, the participant data ®le which, as a result of the P.C.C.F. linking, included the current and previous CSDs that each Drug Treatment Program participant had lived in, was entered and joined to the map's attribute table based on the common CSD geographic code ®eld. At this point a GIS analysis was conducted to ascertain the current geographic distribution of the participants and to determine which CSDs the migrating participants had moved to and from. Statistical analyses were carried out using both parametric and non-parametric methods to identify associations between participants' characteristics and mobility. Variables considered for inclusion were sociodemographic characteristics such as age, gender, aboriginal status, place of residence, income, education, and HIV infection attributed to injection drug use. Clinical variables including CD4 cell count, clinical stage, and physician experience (de®ned by the number of participants each physician had enrolled/followed up on in the program at the time a particular participant joined the treatment program) were also considered in our analysis. Comparison of categorical variables were conducted using chi-square tests and median values were compared by means of the Wilcoxon Rank Sum test. Fisher's exact test was used for 2 2 contingency tables in which any expected cell frequency was less than 5. Stepwise logistic regression was used to determine baseline predictors of migration. Variables included in the regression model were those observed to be statistically signi®cant (P R 0.05) in the univariate analysis. Variables were entered stepwise into the regression model. All reported P-values are two-tailed. The model was adjusted for the number of months participants had been enrolled in the program, since certain participants were not enrolled in the program for the entire study period.
35
3. Results A total of 2405 individuals aged 18 years and over in British Columbia were on anti-HIV therapy between 1 July 1995 and 30 September 1997. After 778 (32.3%) of those subjects were excluded because they did not complete a baseline participant enrollment survey, there were 1627 participants eligible for the study. In comparison to those participants who did not complete a baseline survey, participants who did respond were more likely to be older (median age 37 vs 36 years; p < 0.001), to have a diagnosis of AIDS (17.6% vs 11.9%; P = 0.001), and to be men (14.5% vs 7.7%; P = 0.001). There were no dierences between the two groups with respect to whether the individuals subsequently moved to (P = 0.136) or lived in a community with a population greater than 100,000 (P = 0.143). The vast majority of study participants resided in census subdivisions located in the south western corner of the province with populations greater than 100,000 in 1996. For example, a total of 988 (60.8%) participants resided in the city of Vancouver, 70 (4.3%) in Burnaby, 55 (3.4%) in Surrey, 51 (3.1%) in Victoria, 42 (2.6%) in North Vancouver, and 36 (2.2%) in New Westminster. The remainder of study participants were distributed throughout the rest of the province. In total, study participants resided in 93 (13%) of the 713 census subdivisions located in British Columbia. The 620 census subdivision without study participants all had census populations below 20,000 in 1996. Of the 1627 participants who were included in this analysis, 189 (11.6%) moved census subdivisions during the period of observation. A further 304 (18.7%) participants moved within the same census subdivision during the period of study. Among study participants, 1110 (68.2%) were infected through homosexual contact, 104 (6.4%) were infected through intravenous drug use, 79 (5.0%) through heterosexual contact, and 185 (11.4%) through other (includes individuals with multiple risk factors). Fig. 1 shows the ®nal residence of all Drug Treatment Program Participants who moved to census subdivisions in the south western corner of British Columbia during the period of observation. For the purposes of mapping, we looked at all participants that quali®ed as movers including participants without enrollment data. Including these cases enabled us to map all of the participants that moved, without signi®cantly aecting the percentage of participants that moved to each subdivision. The south western subdivisions make up some of the largest urban areas located in the province including the only two census metropolitan areas (Vancouver and Victoria). As illustrated in this ®gure, the seven census subdivisions with populations greater than
36
E. Wood et al. / Health & Place 6 (2000) 33±40
Fig. 1. Census subdivisions migrated to in southwestern British Columbia by number of participants.
100,000 in 1996 were the destination for nearly half of the study participants which migrated. The most common destinations were Vancouver, Burnaby, and Surrey which received 78 (41.2%) of the 189 migrants. It is noteworthy that our analyses also determined a number of individuals who migrated from urban to rural areas. Over the study period 52 (27.5%) of the 189 movers moved from an urban to a rural subdivision. Of the population that did not move, 1087 (75.6%) remained in an urban area and 350 (24.4%) remained in a rural area. Tables 1 and 2 compare movers (participants who changed census subdivision during the study period) to non-movers, with respect to selected sociodemographic and clinical characteristics. As highlighted in these tables univariate analysis revealed that participants who moved across census subdivision boundaries during the study period were signi®cantly more likely than non-movers to be heterosexual (P = 0.001), more likely to have acquired HIV through injection drug use (P = 0.001), more likely to be of ®rst nation or aboriginal descent (P = 0.027), more likely to come from a CSD with a population lower than 100,000 in 1996 (P = 0.001), and less likely to have graduated from high school (P = 0.008) when compared to participants that did not move. In regards to clinical characteristics, participants who moved were less likely to have AIDS
at baseline (P = 0.013) and a they tend to have a less HIV-experienced physician (P = 0.017). There were no signi®cant dierences between the two groups with respect to CD4 cell count, gender, or age at time of enrollment. The ®nal multivariate model for the baseline factors associated with participant mobility is presented in Table 3. As shown here, residing in a census subdivision with a population of 100,000 or less (P < 0.001), the acquisition of HIV through injection drug use (P < 0.001), the absence of AIDS (P = 0.014), and being heterosexual (P = 0.032) were independently associated with moving census subdivisions during the period of observation. The model was adjusted for the number of months participants had been enrolled in the program.
4. Discussion The overwhelming majority of persons with HIV reside in the urban CSDs located in the south western corner of the province with Vancouver accounting for by far the greatest number persons with HIV. Furthermore, analysis revealed that migration of persons with HIV is contributing to this situation with the urban
E. Wood et al. / Health & Place 6 (2000) 33±40
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Table 1 Comparison of selected sociodemographic characteristics with respect to change in residence during the study period Changed census subdivision during the study period Characteristic Community size R 100,000 > 100,000 Heterosexual No Yes High School Graduation No Yes First Nation/Aboriginal No Yes Age (years) Median Interquartile range Gender Male Female
No n (%)
Yes n (%)
P-value
350 (24.4) 1087 (75.6)
89 (47.1) 100 (52.9)
0.001
1304 (80.2) 134 (8.24)
157 (9.7) 32 (2.0)
0.001
593 (41.2) 845 (58.8)
97 (51.3) 92 (48.7)
0.008
1365 (94.9) 73 (5.1)
172 (91.0) 17 (9.0)
0.027
38 33±44
36 31±43
0.096
1330 (92.5) 108 (7.5)
172 (91.0) 17 (9.0)
0.471
CSDs in the southwestern corner of the province, particularly Vancouver, being the destination for the highest numbers of HIV positive migrants. Migration patterns among persons with HIV similar to what we observed in British Columbia have been identi®ed by researchers in areas of the United States. A study in Texas based on personal interviews with AIDS experts and service providers indicated that the most common move among HIV-infected individuals in that state is rural to urban (Tatum and Schoech,
1992). Research has shown that rural to urban migration is often prompted by factors such as the desire to ®nd physicians and medical centres experienced in treating HIV, to participate in clinical trials, and to access better support services (Tatum and Schoech, 1992; Buehler et al., 1995; Cohn et al., 1994). In contrast, in other parts of the United States researchers have also identi®ed patterns of urban to rural migration by HIV-infected individuals. A study conducted in North Carolina showed that approx. 50% of
Table 2 Comparison of selected clinical characteristics with respect to change in residence during the study period Changed census subdivision during the study period Characteristic Intravenous drug user No Yes AIDS at baseline No Yes Physician experiencea R median (31 participants) > median (31 participants) Baseline CD4 cell count Median Interquartile range a
No n (%)
Yes n (%)
P-value
1265 (88.0) 173 (12.0)
146 (77.3) 43 (22.7)
0.001
1173 (81.6) 265 (18.4)
168 (88.9) 21 (11.1)
0.014
704 (49.0) 734 (51.0)
110 (58.2) 79 (41.8)
0.017
260 135±370
0.522
270 140±380
The number of participants enrolled in the program by each physician.
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E. Wood et al. / Health & Place 6 (2000) 33±40
Table 3 Logistic regression analysisa in which the dependent variable was a change of census subdivision during the study period Variable Community size (>100,000 vs R100,000) AIDS at baseline (Yes vs no) Heterosexual (Yes vs no) Injection Drug Use (Yes vs no) a
Beta coecient
SE
Odds ratio
95% CI
P-value
ÿ1.00
0.16
0.37
(0.27, 0.50)
< 0.001
ÿ0.61
0.25
0.54
(0.33, 0.88)
0.014
0.49
0.23
1.62
(1.04, 2.53)
0.032
0.76
0.21
2.13
(1.43, 3.19)
< 0.001
Model was adjusted for the length of time each participant had been enrolled in the HIV drug treatment program.
the people with HIV in the state's rural eastern counties had been diagnosed outside the study region (Rumley et al., 1991). The majority of studies of urban to rural migration of persons with HIV cite the need for family support as the most common motivation (Ellis and Muschkin, 1996; Fordyce et al., 1997; Davis and Stapleton, 1991; Verghese et al., 1989; Rumley et al., 1991). The migration trends of persons with HIV have a number of implications for both urban and rural areas. For example, in many areas of the US, migration of persons with HIV has been shown to distort incidence and mortality ®gures (Cohn et al., 1994; Buehler et al., 1995). While the immigration and emigration of persons with HIV has had a small net eect on urban areas of the United States, the number of persons with HIV in rural areas has increased (Fordyce et al., 1997). This trend has begun to strain rural health care services in many areas and there is fear that the underestimation of patients infected with HIV is causing maldistribution of HIV-related health care funding and may soon threaten the ability of many rural areas to provide services for these people (Cohn et al., 1994; Davis and Stapleton, 1991). Analysis of the geographic distribution and migration of HIV is an established ®eld of study (Gould, 1993; Cohn et al., 1994; Buehler et al., 1995; Shannon et al., 1990; Smallman-Raynor et al., 1992; Hogg et al., 1995). There has been growing criticism, however, of simply mapping persons with HIV and characterizing migration ¯ows, without recognizing the social dimensions of the illness (Brown, 1995; Wilton, 1996). Recently, a number of studies have made contributions to the understanding of the impetus for migration among persons with HIV (Hogg et al., 1995; Ellis and Muschkin, 1996; Tatum and Schoech, 1992). Although certain trends have been identi®ed, experiences will obviously dier from person to person (Wilton, 1996). Unfortunately, the present study was not able to examine reasons why people moved; however, our results support the work of other investigators who have
suggested that the major impetus for migration among persons with HIV in British Columbia is access to health care (Hogg et al., 1995). For example, the West End of Vancouver is the heart of the province's gay community and researchers have shown that gay and bisexual men are attracted to this centre from smaller cities and rural areas across the country (Brown, 1997; Meyers et al., 1993). In the present analysis, the majority of individuals were gay and bisexual men. Our analysis supports previous work that has suggested that the majority of persons with HIV in British Columbia are middle-aged gay and bisexual men, and it is not surprising that Vancouver out of all CSDs, was the most common destination of migrants and home to the largest population of HIV+ individuals (Strathdee et al., 1994). Similarly, the high number of persons with HIV moving to, and living in, the Vancouver and neighboring CSDs may be explained by the fact that the majority of health-related and social services for people with HIV in the province are located there (Burr et al., 1995). Our analysis supports previous work that has suggested that the accessibility of HIV treatment services, may in¯uence where persons infected with HIV/ AIDS choose to live (Wilton, 1996; Schilder et al., 1993; Hogg et al., 1995). In addition, Vancouver's attractiveness as a destination for persons with HIV is due to the political success the gay community has had in combating homophobia and prejudice against persons with HIV (Brown, 1997). Our analysis also uncovered individuals who were migrating from urban to rural areas. There are several motivating factors that may explain the moves of this kind. Previous studies in other jurisdictions have documented urban to rural migration. Reported reasons for migration to rural areas include the need of social support, to be near family, to change lifestyles, to avoid HIV high risk behaviors, and to ®nd better work/educational opportunities (Fordyce et al., 1997; Ellis and Muschkin, 1996; Rumley et al., 1991; Cohn et al., 1994). It is likely that these factors explain many of
E. Wood et al. / Health & Place 6 (2000) 33±40
the urban to rural migrations we observed in our study population. The main implication of urban to rural migration is that there is potential for the migration of persons HIV into low prevalence areas that may not be the focus of provincial education and prevention programs. Since our analyses determined a number of persons with HIV that are moving from urban to rural areas, the value of making current HIV related information accessible to rural physicians, and devoting energies toward preventative education programs in rural areas should not be underestimated. In British Columbia urban to rural migration is of special concern with respect to aboriginal peoples. In Vancouver, there is an alarmingly high rate of HIV infection among the aboriginal population (Strathdee et al., 1994). There is fear among health care professionals and aboriginal groups that migration of this group could lead to the spread of HIV to the aboriginal communities spread throughout the rural areas of the province (Rekart et al., 1991). The present analysis lends credence to these fears and agrees with previous work that has indicate that it is critical to raise the level of AIDS awareness among urban aboriginals and to prevent HIV spread among this population (Rekart, 1993). Previous work has also suggested that since HIV positive aboriginal people constitute a doubly marginalized population, greater eorts should be made to improve access to HIV testing, counseling, education, and overall health care (Strathdee et al., 1994). Our results suggests that these services should be equally accessible to native people living both urban and rural areas. There are a number of inherent limitations in epidemiologic studies such as ours. Most importantly, participants enrolled in the HIV/AIDS Drug Treatment Program may not be representative of the total HIVpositive population in British Columbia. It has been estimated that approx. 9000 persons have been infected with HIV in the province (Archibald and Loir, 1995). It is unlikely that the study sample is entirely representative of this large, diverse population of HIV-positive men and women. For a number of reasons, such as drug addiction or homelessness, important subgroups of HIV-infected individuals may not be adequately represented, including street youths, intravenous drug users, indigenous peoples, and recent immigrants. In addition, there were signi®cant dierences between those treatment program participants that ®lled out a baseline survey and the non-responders. Non-responders were signi®cantly more likely to be younger, to not have had an AIDS de®ning illness, and to be women. The exclusion of these participants, therefore, may bias our study population towards being older, male, and to have had an AIDS de®ning illness. Nevertheless, the majority of individuals who made up the study population are middle-aged men living in an
39
urban center, which is consistent with the current epidemiology of HIV/AIDS in British Columbia (Strathdee et al., 1994). In summary, we have found that the majority of persons with HIV in British Columbia reside in the urban CSDs in the Southwestern corner of the province, especially the city of Vancouver. Persons with HIV that are choosing to migrate are more likely to be heterosexual, more likely to have acquired HIV through intravenous drug use, and less likely to have AIDS at baseline than the persons with HIV who are not migrating. In addition, individuals who choose to migrate are more likely to come from areas with a population less than 100,000. In British Columbia, epidemiologic research has identi®ed population subgroups in which HIV has spread, and it has been noted that overlap is now occurring among these population sub-groups (Strathdee et al., 1994). As this evolution has occurred there have been growing numbers of HIV infections among persons not traditionally at risk for HIV such as heterosexuals and persons living in rural areas. Population migration plays a central role in this process and the continued study of the migration patterns of persons with HIV is an essential part of characterizing the evolving geography of AIDS. It is critical that our understanding of the AIDS epidemic keep pace with the changing nature of HIV so that education and prevention strategies are properly directed and so that health care resources are distributed where they are most needed.
Acknowledgements This work was supported by the National Health Research Development Program of Health Canada through a National Health Research Scholar Award to Dr Hogg and Dr Montaner, and through a National AIDS Research Scientist Award to Dr Schechter. Evan Wood is supported by a Studentship Grant from the British Columbia Health Research Foundation. We thank Rita Dewletian, Bonnie Devlin, Deborah Hamann-Trou, Myrna Reginaldo, Diane Campbell, Elizabeth Ferris, Ramona Gomes, and Kelly Hsu for their research and administrative assistance.
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Brown, M., 1995. Ironies of distance: an ongoing critique of the geographies of AIDS. Environment and Planning D: Society and Space 13, 159±183. Brown, M.P., 1997. RePlacing Citizenship: AIDS Activism and Radical Democracy. The Guilford Press, New York. Buehler, J.W., Frey, R.L., Chu, S.Y., 1995. The migration of persons with AIDS: data from 12 states, 1985 to 1992. AIDS Mortality Project Group. American Journal of Public Health 85, 1552±1555. Burr, K.F., Costanzo, G.A., Hayes, M.V., Ying, C.M., McKee, B., 1995. Mortality and health status in Vancouver: an analysis by neighborhood areas, 1995. Division of Vital Statistics. Cohn, S.E., Klein, J.D., Mohr, J.E., van der Horst, C.M., Weber, D.J., 1994. The geography of AIDS: patterns of urban and rural migration. Southern Medical Journal 87, 599±606. Davis, K., Stapleton, J., 1991. Migration to rural areas by HIV patients: impact on HIV-related healthcare use. Infect. Control Hosp. Epid. 12, 540±543. Ellis, M., Muschkin, C., 1996. Migration of persons with AIDS Ð a search for support from elderly parents? Social Science & Medicine 43, 1109±1118. Environmental Systems Research Institute, 1996. ArcView GIS. E.S.R.I., Redlands, CA. Fordyce, E.J., Thomas, P., Shum, R., 1997. Evidence of an increasing AIDS burden in rural America. Statistical Bulletin Ð Metropolitan Insurance Companies 78, 2±9. Gould, P., 1993. The Slow Plague: A Geography of the AIDS Pandemic. Blackwell, New York. Hogg, R.S., Heath, K.V., Strathdee, S.A., Montaner, J.S., O'Shaughnessy, M.V., Schechter, M.T., 1996. HIV/AIDS mortality in Canada: evidence of gender, regional and local area dierentials. Aids 10, 889±894. Hogg, R.S., Schechter, M.T., Schilder, A., Strathdee, S.A., Goldstone, I.L., O'Shaughnessy, M.V., 1995. Access to health care and geographic mobility of HIV/AIDS patients. AIDS Patient Care 9, 297±302.
Hogg, R.S., Whitehead, J., Ricketts, ., Heath, K.V., Ng, E., Lalonde, P., Schechter, M.T., 1997. Patterns of geographic mobility of persons with AIDS in Canada from time of AIDS index diagnosis to death. Clin. Invest. Med. 20, 77± 83. Meyers, T., Godin, G., Calzavara, L., Lambert, J., Locker, D., 1993. The Canadian survey of gay and bisexual men and HIV infection: men's survey. Canadian AIDS Society, Ottawa. Rekart, M.L., 1993. Developing a strategy for urban aboriginal AIDS education and prevention. In: Int. Conf. AIDS, vol. 9, p. 109, (abstract no. WS-D106±103). Rekart, M.L., Chan, S., Barnett, J., Lawrence, C., Manzon, L., 1991. HIV and North American aboriginal peoples. In: Int. Conf. AIDS, vol. 7, p. 357, (abstract no. M.C.3237). Rumley, R.L., Shappley, N.C., Waivers, L.E., Esinhart, J.D., 1991. AIDS in rural eastern North Carolina Ð patient migration: a rural AIDS burden. Aids 5, 1373±1378. Shannon, G.W., et al., 1991. The Geography of AIDS: Origins and Course of an Epidemic. Guilford Press, New York. Shannon, G.W., Pyle, G.F., Bashur, R., 1990. The Geography of AIDS. Guilford Press, New York. Smallman-Raynor, M., Cli, A., Hagget, P., 1992. Atlas of AIDS. Blackwell, Oxford. Strathdee, S., Schecter, M.T., Hogg, R.S., O'Shaughnessy, M.V., 1994. Current trends in HIV/AIDS epidemiology in British Columbia. BC Medical Journal 36, 98±115. Tatum, P.S., Schoech, D., 1992. Migration of persons with HIV Disease: the search for care. AIDS Public Policy Journal 7, 56. Verghese, A., Berk, S.L., Sarubbi, F., 1989. Urbs in rure: human immunode®ciency virus infection in rural Tennessee. Journal of Infectious Diseases 160, 1051±1055. Wilton, R.D., 1996. Diminished worlds? The geography of everyday life with HIV/AIDS. Health and Place 2, 69±83.
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Determinants of geographic mobility among participants in a population-based HIV/AIDS drug treatment program Evan Wood a, Benita Yip a, Nada Gataric a, Julio S.G. Montaner a, b, Michael V. O'Shaughnessy a, c, Martin T. Schechter a, d, Robert S. Hogg a, d,* a
British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada b Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Colombia, Canada c Department of Pathology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada d Health Care and Epidemiology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
Abstract This study was undertaken to determine the geographic distribution and patterns of migration of persons with HIV in British Columbia. Our analysis was restricted to all HIV-positive men and women aged 18 years and over who had completed a participant survey and were enrolled in the HIV/AIDS Drug Treatment Program between September 1992 and September 1997. Patterns of migration were determined by examining participants whose postal code changed between July 1995 and September 1997. Statistical analysis were carried out using both parametric and non-parametric methodologies. Stepwise logistic regression was used to determine baseline predictors of migration. The ®nal multivariate model revealed that residing in a census subdivision with a population less than 100,000, being heterosexual, acquiring HIV through intravenous drug use, and the absence of AIDS at baseline were all independently associated with moving census subdivisions during the period of observation. In summary, our analyses demonstrate the need for the continued study of the evolving geography and migration patterns of persons with HIV. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: HIV; AIDS; Migration; Canada; British Columbia; Antiretroviral therapy; Population based cohort
1. Introduction Previous studies of migration and HIV/AIDS in North America have shown considerable mobility among persons with HIV (Cohn et al., 1994; Davis and Stapleton, 1991; Ellis and Muschkin, 1996; Vergh-
* Corresponding author. Tel.: +1 (604) 631-5516; fax: +1 (604) 631-5464. E-mail address: [email protected] (R.S. Hogg).
ese et al., 1989; Rumley et al., 1991). Researchers have characterized patterns of rural to urban and urban to rural migration, and identi®ed motivating factors such as the need for social services, family support, and specialized health care (Ellis and Muschkin, 1996; Tatum and Schoech, 1992; Davis and Stapleton, 1991; Fordyce et al., 1997; Rumley et al., 1991). Analysis of the migration of persons with HIV has several implications. Of foremost importance is determining where people with HIV and AIDS are choosing to reside at dierent stages of their illness so that
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E. Wood et al. / Health & Place 6 (2000) 33±40
health care resources are most appropriately allocated. Similarly, recognizing the evolving geography of HIV is important so that HIV/AIDS education and prevention strategies are directed as eciently and eectively as possible. Various studies have contributed to understanding the distribution and spread of HIV/AIDS by mapping the origin of the HIV virus and its diusion over space (Gould, 1993; Shannon et al., 1990, Smallman-Raynor et al., 1992). This work has determined that HIV/ AIDS has tended to cluster in certain areas of the urban landscape and among certain population subgroups such as homosexuals and intravenous drug users (Shannon et al., 1991; Gould, 1993). It has been suggested, however, that as the epidemic evolves and diuses, considerable overlap can be expected between these dierent sub-groups, and a growing number of new HIV infections among persons not traditionally at risk (Strathdee et al., 1994). Analysis of the migration of persons with HIV is one of the best ways to anticipate how the epidemic will evolve, and to direct the necessary steps to try and avoid further spread. In Canada, analysis of the geographic distribution and patterns of migration of persons with HIV/AIDS has revealed that the majority of HIV+ individuals reside in the large metropolitan cities and that the overall rate of inter-provincial migration by persons with HIV is comparable to that of the general Canadian population (Hogg et al., 1996, 1997). These studies linked data on the place of AIDS diagnosis to death registration systems and were restricted to looking at inter-provincial migration. As a result, analysis has been lacking on the geographic distribution and migration patterns of persons with HIV within provinces. This study was undertaken to determine the geographic distribution and patterns of migration of persons with HIV in British Columbia. Speci®cally, we sought to determine where in the province persons with HIV are living, the rate of migration within this population, and where individuals who are migrating are moving to and from. In addition, we have investigated some of the social and health-related factors associated with individuals' decisions to migrate.
2. Methods In British Columbia anti-HIV drugs have been centrally distributed at no cost to eligible HIV-infected individuals since 1986. In October 1992, the HIV/AIDS Drug Treatment Program became the responsibility of the British Columbia Centre for Excellence in HIV/ AIDS (the Centre) which is located in downtown Vancouver. From 1986 to 1998, a total of 5005 HIV-posi-
tive British Columbians received anti-HIV therapy. Of these, 4171 have been enrolled in the Drug Treatment Program and 2384 are currently receiving anti-HIV therapy. The current criteria for treatment eligibility is based on a documented HIV infection and a CD4 cell count consistently below 500 cells/mm3 or a plasma viral load determination greater than 5000 copies/ml (British Columbia Centre for Excellence in HIV/AIDS, 1995). Participants meeting these criteria are enrolled in the program by their general practitioner on submission of a prescription for antiretroviral or approved antimicrobial medications. The Centre's Drug Treatment Program remains the only free source of antiretroviral medications in the province. Physicians enrolling an HIV-positive individual into the Centre's Drug Treatment Program must complete a drug request enrollment form. The enrollment form acts as a legal prescription and compiles information on the HIV-positive applicant's address and enrolling physician, past HIV-speci®c drug history, CD4 cell counts, and current drug requests. Each request is reviewed by a quali®ed practitioner to ensure that it meets the Centre's established therapeutic guidelines. Approved prescriptions are renewed every 2 months. At the time of the initial re®ll each participant is asked to complete an enrollment survey and program consent form, while their physician is asked to complete a clinical staging form. Participant surveys and clinical staging forms are completed annually. The participant survey elicits information about the participant's socioeconomic status, social support, clinical status, and current and previous use of HIV-related medications and complementary therapies. Data from the surveys were used to create sociodemographic pro®les of the participants that quali®ed for the study. Our analysis was restricted to all HIV-positive men and women aged 18 years and over, who had completed a participant survey, and were enrolled into the program between September 1992 and September 1997. As postal code histories have only been maintained since July 1995, we restricted our analysis to those participants that started or were still on antiHIV medication after that date. The primary endpoint in this analysis was a change in Census Subdivision. Patterns of migration were determined by examining participants whose postal code changed between July 1995 and September 1997. Census subdivision (CSD) is the term used by Statistics Canada to de®ne municipalities or geographic areas that have been created as equivalents of municipalities for the dissemination of statistical data. As we were not interested in movements within the same municipality, only those participants whose postal code changes re¯ected a movement to a new census subdivision quali®ed as migrants in this analysis. Movements between CSDs were determined by linking
E. Wood et al. / Health & Place 6 (2000) 33±40
each participant's postal code or codes to CSDs using Statistics Canada's Postal Code Conversion File (P.C.C.F.). This ®le generated a CSD geographic code for the CSD with which each participant's current and previous postal codes are associated. Once this linking was performed, ArcView Geographical Information System (GIS) software was used to map the geographic distribution and migration patterns of the participants based on their current and previous CSD codes (Environmental Systems Research Institute, 1996). A digital cartographic ®le of British Columbia with the boundaries of all CSDs was entered into the GIS. This ®le contained a digital map of the province with all Census Subdivision boundaries overlaid and an attribute information table which contained the CSD geographic codes for each of the 713 Census Subdivisions in the province. Similarly, the participant data ®le which, as a result of the P.C.C.F. linking, included the current and previous CSDs that each Drug Treatment Program participant had lived in, was entered and joined to the map's attribute table based on the common CSD geographic code ®eld. At this point a GIS analysis was conducted to ascertain the current geographic distribution of the participants and to determine which CSDs the migrating participants had moved to and from. Statistical analyses were carried out using both parametric and non-parametric methods to identify associations between participants' characteristics and mobility. Variables considered for inclusion were sociodemographic characteristics such as age, gender, aboriginal status, place of residence, income, education, and HIV infection attributed to injection drug use. Clinical variables including CD4 cell count, clinical stage, and physician experience (de®ned by the number of participants each physician had enrolled/followed up on in the program at the time a particular participant joined the treatment program) were also considered in our analysis. Comparison of categorical variables were conducted using chi-square tests and median values were compared by means of the Wilcoxon Rank Sum test. Fisher's exact test was used for 2 2 contingency tables in which any expected cell frequency was less than 5. Stepwise logistic regression was used to determine baseline predictors of migration. Variables included in the regression model were those observed to be statistically signi®cant (P R 0.05) in the univariate analysis. Variables were entered stepwise into the regression model. All reported P-values are two-tailed. The model was adjusted for the number of months participants had been enrolled in the program, since certain participants were not enrolled in the program for the entire study period.
35
3. Results A total of 2405 individuals aged 18 years and over in British Columbia were on anti-HIV therapy between 1 July 1995 and 30 September 1997. After 778 (32.3%) of those subjects were excluded because they did not complete a baseline participant enrollment survey, there were 1627 participants eligible for the study. In comparison to those participants who did not complete a baseline survey, participants who did respond were more likely to be older (median age 37 vs 36 years; p < 0.001), to have a diagnosis of AIDS (17.6% vs 11.9%; P = 0.001), and to be men (14.5% vs 7.7%; P = 0.001). There were no dierences between the two groups with respect to whether the individuals subsequently moved to (P = 0.136) or lived in a community with a population greater than 100,000 (P = 0.143). The vast majority of study participants resided in census subdivisions located in the south western corner of the province with populations greater than 100,000 in 1996. For example, a total of 988 (60.8%) participants resided in the city of Vancouver, 70 (4.3%) in Burnaby, 55 (3.4%) in Surrey, 51 (3.1%) in Victoria, 42 (2.6%) in North Vancouver, and 36 (2.2%) in New Westminster. The remainder of study participants were distributed throughout the rest of the province. In total, study participants resided in 93 (13%) of the 713 census subdivisions located in British Columbia. The 620 census subdivision without study participants all had census populations below 20,000 in 1996. Of the 1627 participants who were included in this analysis, 189 (11.6%) moved census subdivisions during the period of observation. A further 304 (18.7%) participants moved within the same census subdivision during the period of study. Among study participants, 1110 (68.2%) were infected through homosexual contact, 104 (6.4%) were infected through intravenous drug use, 79 (5.0%) through heterosexual contact, and 185 (11.4%) through other (includes individuals with multiple risk factors). Fig. 1 shows the ®nal residence of all Drug Treatment Program Participants who moved to census subdivisions in the south western corner of British Columbia during the period of observation. For the purposes of mapping, we looked at all participants that quali®ed as movers including participants without enrollment data. Including these cases enabled us to map all of the participants that moved, without signi®cantly aecting the percentage of participants that moved to each subdivision. The south western subdivisions make up some of the largest urban areas located in the province including the only two census metropolitan areas (Vancouver and Victoria). As illustrated in this ®gure, the seven census subdivisions with populations greater than
36
E. Wood et al. / Health & Place 6 (2000) 33±40
Fig. 1. Census subdivisions migrated to in southwestern British Columbia by number of participants.
100,000 in 1996 were the destination for nearly half of the study participants which migrated. The most common destinations were Vancouver, Burnaby, and Surrey which received 78 (41.2%) of the 189 migrants. It is noteworthy that our analyses also determined a number of individuals who migrated from urban to rural areas. Over the study period 52 (27.5%) of the 189 movers moved from an urban to a rural subdivision. Of the population that did not move, 1087 (75.6%) remained in an urban area and 350 (24.4%) remained in a rural area. Tables 1 and 2 compare movers (participants who changed census subdivision during the study period) to non-movers, with respect to selected sociodemographic and clinical characteristics. As highlighted in these tables univariate analysis revealed that participants who moved across census subdivision boundaries during the study period were signi®cantly more likely than non-movers to be heterosexual (P = 0.001), more likely to have acquired HIV through injection drug use (P = 0.001), more likely to be of ®rst nation or aboriginal descent (P = 0.027), more likely to come from a CSD with a population lower than 100,000 in 1996 (P = 0.001), and less likely to have graduated from high school (P = 0.008) when compared to participants that did not move. In regards to clinical characteristics, participants who moved were less likely to have AIDS
at baseline (P = 0.013) and a they tend to have a less HIV-experienced physician (P = 0.017). There were no signi®cant dierences between the two groups with respect to CD4 cell count, gender, or age at time of enrollment. The ®nal multivariate model for the baseline factors associated with participant mobility is presented in Table 3. As shown here, residing in a census subdivision with a population of 100,000 or less (P < 0.001), the acquisition of HIV through injection drug use (P < 0.001), the absence of AIDS (P = 0.014), and being heterosexual (P = 0.032) were independently associated with moving census subdivisions during the period of observation. The model was adjusted for the number of months participants had been enrolled in the program.
4. Discussion The overwhelming majority of persons with HIV reside in the urban CSDs located in the south western corner of the province with Vancouver accounting for by far the greatest number persons with HIV. Furthermore, analysis revealed that migration of persons with HIV is contributing to this situation with the urban
E. Wood et al. / Health & Place 6 (2000) 33±40
37
Table 1 Comparison of selected sociodemographic characteristics with respect to change in residence during the study period Changed census subdivision during the study period Characteristic Community size R 100,000 > 100,000 Heterosexual No Yes High School Graduation No Yes First Nation/Aboriginal No Yes Age (years) Median Interquartile range Gender Male Female
No n (%)
Yes n (%)
P-value
350 (24.4) 1087 (75.6)
89 (47.1) 100 (52.9)
0.001
1304 (80.2) 134 (8.24)
157 (9.7) 32 (2.0)
0.001
593 (41.2) 845 (58.8)
97 (51.3) 92 (48.7)
0.008
1365 (94.9) 73 (5.1)
172 (91.0) 17 (9.0)
0.027
38 33±44
36 31±43
0.096
1330 (92.5) 108 (7.5)
172 (91.0) 17 (9.0)
0.471
CSDs in the southwestern corner of the province, particularly Vancouver, being the destination for the highest numbers of HIV positive migrants. Migration patterns among persons with HIV similar to what we observed in British Columbia have been identi®ed by researchers in areas of the United States. A study in Texas based on personal interviews with AIDS experts and service providers indicated that the most common move among HIV-infected individuals in that state is rural to urban (Tatum and Schoech,
1992). Research has shown that rural to urban migration is often prompted by factors such as the desire to ®nd physicians and medical centres experienced in treating HIV, to participate in clinical trials, and to access better support services (Tatum and Schoech, 1992; Buehler et al., 1995; Cohn et al., 1994). In contrast, in other parts of the United States researchers have also identi®ed patterns of urban to rural migration by HIV-infected individuals. A study conducted in North Carolina showed that approx. 50% of
Table 2 Comparison of selected clinical characteristics with respect to change in residence during the study period Changed census subdivision during the study period Characteristic Intravenous drug user No Yes AIDS at baseline No Yes Physician experiencea R median (31 participants) > median (31 participants) Baseline CD4 cell count Median Interquartile range a
No n (%)
Yes n (%)
P-value
1265 (88.0) 173 (12.0)
146 (77.3) 43 (22.7)
0.001
1173 (81.6) 265 (18.4)
168 (88.9) 21 (11.1)
0.014
704 (49.0) 734 (51.0)
110 (58.2) 79 (41.8)
0.017
260 135±370
0.522
270 140±380
The number of participants enrolled in the program by each physician.
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E. Wood et al. / Health & Place 6 (2000) 33±40
Table 3 Logistic regression analysisa in which the dependent variable was a change of census subdivision during the study period Variable Community size (>100,000 vs R100,000) AIDS at baseline (Yes vs no) Heterosexual (Yes vs no) Injection Drug Use (Yes vs no) a
Beta coecient
SE
Odds ratio
95% CI
P-value
ÿ1.00
0.16
0.37
(0.27, 0.50)
< 0.001
ÿ0.61
0.25
0.54
(0.33, 0.88)
0.014
0.49
0.23
1.62
(1.04, 2.53)
0.032
0.76
0.21
2.13
(1.43, 3.19)
< 0.001
Model was adjusted for the length of time each participant had been enrolled in the HIV drug treatment program.
the people with HIV in the state's rural eastern counties had been diagnosed outside the study region (Rumley et al., 1991). The majority of studies of urban to rural migration of persons with HIV cite the need for family support as the most common motivation (Ellis and Muschkin, 1996; Fordyce et al., 1997; Davis and Stapleton, 1991; Verghese et al., 1989; Rumley et al., 1991). The migration trends of persons with HIV have a number of implications for both urban and rural areas. For example, in many areas of the US, migration of persons with HIV has been shown to distort incidence and mortality ®gures (Cohn et al., 1994; Buehler et al., 1995). While the immigration and emigration of persons with HIV has had a small net eect on urban areas of the United States, the number of persons with HIV in rural areas has increased (Fordyce et al., 1997). This trend has begun to strain rural health care services in many areas and there is fear that the underestimation of patients infected with HIV is causing maldistribution of HIV-related health care funding and may soon threaten the ability of many rural areas to provide services for these people (Cohn et al., 1994; Davis and Stapleton, 1991). Analysis of the geographic distribution and migration of HIV is an established ®eld of study (Gould, 1993; Cohn et al., 1994; Buehler et al., 1995; Shannon et al., 1990; Smallman-Raynor et al., 1992; Hogg et al., 1995). There has been growing criticism, however, of simply mapping persons with HIV and characterizing migration ¯ows, without recognizing the social dimensions of the illness (Brown, 1995; Wilton, 1996). Recently, a number of studies have made contributions to the understanding of the impetus for migration among persons with HIV (Hogg et al., 1995; Ellis and Muschkin, 1996; Tatum and Schoech, 1992). Although certain trends have been identi®ed, experiences will obviously dier from person to person (Wilton, 1996). Unfortunately, the present study was not able to examine reasons why people moved; however, our results support the work of other investigators who have
suggested that the major impetus for migration among persons with HIV in British Columbia is access to health care (Hogg et al., 1995). For example, the West End of Vancouver is the heart of the province's gay community and researchers have shown that gay and bisexual men are attracted to this centre from smaller cities and rural areas across the country (Brown, 1997; Meyers et al., 1993). In the present analysis, the majority of individuals were gay and bisexual men. Our analysis supports previous work that has suggested that the majority of persons with HIV in British Columbia are middle-aged gay and bisexual men, and it is not surprising that Vancouver out of all CSDs, was the most common destination of migrants and home to the largest population of HIV+ individuals (Strathdee et al., 1994). Similarly, the high number of persons with HIV moving to, and living in, the Vancouver and neighboring CSDs may be explained by the fact that the majority of health-related and social services for people with HIV in the province are located there (Burr et al., 1995). Our analysis supports previous work that has suggested that the accessibility of HIV treatment services, may in¯uence where persons infected with HIV/ AIDS choose to live (Wilton, 1996; Schilder et al., 1993; Hogg et al., 1995). In addition, Vancouver's attractiveness as a destination for persons with HIV is due to the political success the gay community has had in combating homophobia and prejudice against persons with HIV (Brown, 1997). Our analysis also uncovered individuals who were migrating from urban to rural areas. There are several motivating factors that may explain the moves of this kind. Previous studies in other jurisdictions have documented urban to rural migration. Reported reasons for migration to rural areas include the need of social support, to be near family, to change lifestyles, to avoid HIV high risk behaviors, and to ®nd better work/educational opportunities (Fordyce et al., 1997; Ellis and Muschkin, 1996; Rumley et al., 1991; Cohn et al., 1994). It is likely that these factors explain many of
E. Wood et al. / Health & Place 6 (2000) 33±40
the urban to rural migrations we observed in our study population. The main implication of urban to rural migration is that there is potential for the migration of persons HIV into low prevalence areas that may not be the focus of provincial education and prevention programs. Since our analyses determined a number of persons with HIV that are moving from urban to rural areas, the value of making current HIV related information accessible to rural physicians, and devoting energies toward preventative education programs in rural areas should not be underestimated. In British Columbia urban to rural migration is of special concern with respect to aboriginal peoples. In Vancouver, there is an alarmingly high rate of HIV infection among the aboriginal population (Strathdee et al., 1994). There is fear among health care professionals and aboriginal groups that migration of this group could lead to the spread of HIV to the aboriginal communities spread throughout the rural areas of the province (Rekart et al., 1991). The present analysis lends credence to these fears and agrees with previous work that has indicate that it is critical to raise the level of AIDS awareness among urban aboriginals and to prevent HIV spread among this population (Rekart, 1993). Previous work has also suggested that since HIV positive aboriginal people constitute a doubly marginalized population, greater eorts should be made to improve access to HIV testing, counseling, education, and overall health care (Strathdee et al., 1994). Our results suggests that these services should be equally accessible to native people living both urban and rural areas. There are a number of inherent limitations in epidemiologic studies such as ours. Most importantly, participants enrolled in the HIV/AIDS Drug Treatment Program may not be representative of the total HIVpositive population in British Columbia. It has been estimated that approx. 9000 persons have been infected with HIV in the province (Archibald and Loir, 1995). It is unlikely that the study sample is entirely representative of this large, diverse population of HIV-positive men and women. For a number of reasons, such as drug addiction or homelessness, important subgroups of HIV-infected individuals may not be adequately represented, including street youths, intravenous drug users, indigenous peoples, and recent immigrants. In addition, there were signi®cant dierences between those treatment program participants that ®lled out a baseline survey and the non-responders. Non-responders were signi®cantly more likely to be younger, to not have had an AIDS de®ning illness, and to be women. The exclusion of these participants, therefore, may bias our study population towards being older, male, and to have had an AIDS de®ning illness. Nevertheless, the majority of individuals who made up the study population are middle-aged men living in an
39
urban center, which is consistent with the current epidemiology of HIV/AIDS in British Columbia (Strathdee et al., 1994). In summary, we have found that the majority of persons with HIV in British Columbia reside in the urban CSDs in the Southwestern corner of the province, especially the city of Vancouver. Persons with HIV that are choosing to migrate are more likely to be heterosexual, more likely to have acquired HIV through intravenous drug use, and less likely to have AIDS at baseline than the persons with HIV who are not migrating. In addition, individuals who choose to migrate are more likely to come from areas with a population less than 100,000. In British Columbia, epidemiologic research has identi®ed population subgroups in which HIV has spread, and it has been noted that overlap is now occurring among these population sub-groups (Strathdee et al., 1994). As this evolution has occurred there have been growing numbers of HIV infections among persons not traditionally at risk for HIV such as heterosexuals and persons living in rural areas. Population migration plays a central role in this process and the continued study of the migration patterns of persons with HIV is an essential part of characterizing the evolving geography of AIDS. It is critical that our understanding of the AIDS epidemic keep pace with the changing nature of HIV so that education and prevention strategies are properly directed and so that health care resources are distributed where they are most needed.
Acknowledgements This work was supported by the National Health Research Development Program of Health Canada through a National Health Research Scholar Award to Dr Hogg and Dr Montaner, and through a National AIDS Research Scientist Award to Dr Schechter. Evan Wood is supported by a Studentship Grant from the British Columbia Health Research Foundation. We thank Rita Dewletian, Bonnie Devlin, Deborah Hamann-Trou, Myrna Reginaldo, Diane Campbell, Elizabeth Ferris, Ramona Gomes, and Kelly Hsu for their research and administrative assistance.
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