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Sociobehavioral Factors Affect Clinical
Outcomes Apart From HIV Factors in Swiss Cohort
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17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
- The findings illustrate how strongly socioeconomic and behavioral variables can sway results in cohort studies, especially in studies that cannot or do not try to adjust for such variables.-
Sociobehavioral factors including nationality, employment, gender, and HIV transmission group predicted viral suppression and death independently of clinical factors like CD4 count and viral load in the Swiss HIV Cohort Study (SHCS) [1]. Olivia Keiser and SHCS colleagues found ominous RNA response and death risks not only in injection drug users (IDUs), but also in young immigrants, married women, and older heterosexual men.
The study involved all SHCS members who entered the cohort from 2000 through 2009. Keiser used a method called latent class analysis to group the 4483 cohort members into seven clusters:
· 1568 older gay men (median age 38) who were European, had stable or occasional partners, and were employed
· 156 younger gay men (median age 30) mainly from northwest or eastern Europe, Latin America, and Asia, often living in stable or unstable partnerships
· 884 mixed heterosexuals (median age 37) including men and women
· 431 older heterosexual men (median age 57) in unstable partnerships, who were self-employed or on pensions
· 589 former or current IDUs (median age 36), mostly unemployed
· 444 young immigrants (median age 30), mostly women, mainly from sub-Saharan Africa, often unemployed and with occasional partners
· 411 married women (median age 32) or women in stable partnerships who were housewives or employed
The SHCS team focused on 3031 previously untreated people (68% of the 4483) who started antiretroviral therapy during follow-up. Median CD4 counts at cohort entry and starting therapy were 332 and 225 for older gays, 356 and 204 for younger gays, 282 and 177 for mixed heterosexuals, 342 and 185 for older heterosexual men, 286 and 202 for IDUs, 264 and 190 for young immigrants, and 303 and 207 for married women. Between-group CD4 differences were highly statistically significant (P < 0.0001).
Keiser and coworkers assessed the impact of sociobehavioral group on three endpoints--loss to follow-up in the cohort, viral suppression, and death. The statistical model considered CD4 count, HIV disease stage, viral load, type of antiretroviral regimen, and (in further analyses) age and gender. Compared with older gay men, two groups had a higher risk of loss to follow-up: IDUs (adjusted hazard ratio [HR] 2.6, 95% confidence interval [CI] 1.8 to 3.7) and young immigrants (HR 2.3, 95% CI 1.6 to 3.4).
All groups except younger gay men had reduced chances of viral suppression when compared with older gays. For IDUs, the chance of viral suppression was 80% lower than in older gays, for married women 80% lower, for young immigrants 80% lower, for older heterosexual men 60% lower, and for mixed heterosexuals 50% lower.
For the mortality analysis, the investigators put older and younger gay men into one group because no younger gays died. Two groups had a higher risk of dying than gay men during 4 years of follow-up. IDUs had more than a quadrupled risk of death (HR 4.4, 95% CI 2.5 to 7.7), and older heterosexual men had more than a tripled risk (HR 3.3, 95% CI 1.8 to 5.8). Statistical analyses that also factored in age and gender determined that the death risk fell from 3.3 to 2.7 (95% CI 1.4 to 5.3) in older heterosexual men, while climbing from 4.4 to 5.4 (95% CI 3.0 to 9.6) in IDUs.
In planning HIV care, the researchers recommended that physicians pay "specific attention . . . not only to IDUs, but also to young immigrants, married women, and older heterosexual men." Keiser and colleagues suggested that these groups may benefit from "targeted interventions, for example to improve adherence."
The findings illustrate how strongly socioeconomic and behavioral variables can sway results in cohort studies, especially in studies that cannot or do not try to adjust for such variables.
Reference
1. Keiser O, Spycher B, Rauch A, et al. Mortality and loss to follow-up by socio-behavioral group in patients starting ART in the Swiss HIV Cohort Study. 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 528. http://www.retroconference.org/2010/PDFs/528.pdf.
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