Investigating site-level longitudinal effects of population health interventions: Gay-Straight Alliances and school safety

Gu Li; Amery D Wu; Sheila K Marshall; Ryan J Watson; Jones K Adjei; Minjeong Park; Elizabeth M Saewyc

doi:10.1016/j.ssmph.2019.100350

Investigating site-level longitudinal effects of population health interventions: Gay-Straight Alliances and school safety

SSM Popul Health. 2019 Jan 11:7:100350. doi: 10.1016/j.ssmph.2019.100350. eCollection 2019 Apr.

Authors

Gu Li^{1

2}, Amery D Wu^{1

3}, Sheila K Marshall^{1

4}, Ryan J Watson^{1

5}, Jones K Adjei^{1

6}, Minjeong Park¹, Elizabeth M Saewyc¹

Affiliations

¹ Stigma and Resilience Among Vulnerable Youth Centre, School of Nursing, University of British Columbia, T201 2211 Wesbrook Mall, Vancouver, BC, Canada V6T 2B5.
² Social Health Lab, Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, BC, Canada V6T 1Z4.
³ Department of Educational and Counselling Psychology, and Special Education, University of British Columbia, 2125 Main Mall, Vancouver, BC, Canada V6T 1Z4.
⁴ School of Social Work, University of British Columbia, 2080 West Mall, Vancouver, BC, Canada V6T 1Z2.
⁵ Department of Human Development and Family Studies, University of Connecticut, 348 Mansfield Rd U1058 Storrs, Storrs, CT 06269, USA.
⁶ School of Arts and Sciences, Red Deer College, 100 College Boulevard, P.O. Box 5005, Red Deer, AB, Canada T4N 5H5.

Abstract

There is limited research on evaluating nonrandomized population health interventions. We aimed to introduce a new approach for assessing site-level longitudinal effects of population health interventions (SLEPHI) by innovatively applying multiple group multilevel (MG-ML) modeling to repeated cycles of cross-sectional data collected from different individuals of the same sites at different times, a design commonly employed in public health research. For illustration, we used this SLEPHI method to examine the influence of Gay-Straight Alliances (GSAs) on school-level perceived safety among lesbian, gay, and bisexual (LGB) and heterosexual (HET) adolescents. Individual-level data of perceived school safety came from 1625 LGB students (67.4% female; mean age, 15.7 years) and 37,597 HET students (50.2% female; mean age, 15.4 years) attending Grades 7-12 in 135 schools, which participated in 3 British Columbia Adolescent Health Surveys (BCAHS: 2003, 2008, 2013) in Canada. School-level data of GSA length since established were collected by telephone in 2008 and 2014. Nested MG-ML models suggested that after accounting for secular trend, cohort effects, measurement error, measurement equivalence, and student age, GSA length linearly related to increased school-level perceived safety among LGB students (b = 1.57, SE = 0.21, p < .001, β = 0.32) and also among HET students (β = 0.34 in 2003 & 2013, β = 0.32 in 2008) although statistical differences between years for HET youth were likely due to the large sample size. By conducting MG-ML analysis on repeated cross-sectional surveys, this SLEPHI method accounted for many confounding factors and followed schools for a longer period than most longitudinal designs can follow individuals. Therefore, we drew a stronger conclusion than previous observational research about GSAs and LGB students' well-being. The SLEPHI method can be widely applied to other repeated cycles of cross-sectional data in public health research.

Keywords: Adolescents; Canada; DiD, difference-in-differences; GSA, Gay-Straight Alliances; Gay-Straight Alliances; ITS, interrupted time series; LGB, lesbian, gay, and bisexual; LRV, latent response variable; Lesbian/gay/bisexual; MG-ML; MG-ML, multiple group multilevel; RCT, randomized controlled trial; SLEPHI; SLEPHI, site-level longitudinal effects of population health interventions.