National Centre for Register-Based Research, Aarhus University, Aarhus, Denmark.
Neuropsychiatric Epidemiology Research Unit, School of Population and Global Health, The University of Western Australia, Perth, WA, Australia.
Aust N Z J Psychiatry. 2021 Dec;55(12):1157-1165. doi: 10.1177/00048674211009615. Epub 2021 May 13.
An association between schizophrenia and urbanicity has long been observed, with studies in many countries, including several from Denmark, reporting that individuals born/raised in densely populated urban settings have an increased risk of developing schizophrenia compared to those born/raised in rural settings. However, these findings have not been replicated in all studies. In particular, a Western Australian study showed a gradient in the opposite direction which disappeared after adjustment for covariates. Given the different findings for Denmark and Western Australia, our aim was to investigate the relationship between schizophrenia and urbanicity in these two regions to determine which factors may be influencing the relationship.
We used population-based cohorts of children born alive between 1980 and 2001 in Western Australia ( = 428,784) and Denmark ( = 1,357,874). Children were categorised according to the level of urbanicity of their mother's residence at time of birth and followed-up through to 30 June 2015. Linkage to State-based registers provided information on schizophrenia diagnosis and a range of covariates. Rates of being diagnosed with schizophrenia for each category of urbanicity were estimated using Cox proportional hazards models adjusted for covariates.
During follow-up, 1618 (0.4%) children in Western Australia and 11,875 (0.9%) children in Denmark were diagnosed with schizophrenia. In Western Australia, those born in the most remote areas did not experience lower rates of schizophrenia than those born in the most urban areas (hazard ratio = 1.02 [95% confidence interval: 0.81, 1.29]), unlike their Danish counterparts (hazard ratio = 0.62 [95% confidence interval: 0.58, 0.66]). However, when the Western Australian cohort was restricted to children of non-Aboriginal Indigenous status, results were consistent with Danish findings (hazard ratio = 0.46 [95% confidence interval: 0.29, 0.72]).
Our study highlights the potential for disadvantaged subgroups to mask the contribution of urban-related risk factors to risk of schizophrenia and the importance of stratified analysis in such cases.
长期以来，人们一直观察到精神分裂症与城市化之间存在关联，许多国家（包括丹麦）的研究报告称，与在农村环境中出生和成长的人相比，在人口密集的城市环境中出生和成长的个体患精神分裂症的风险增加。然而，这些发现并非在所有研究中都得到了证实。特别是，西澳大利亚州的一项研究显示出相反方向的梯度，但在调整协变量后梯度消失了。鉴于丹麦和西澳大利亚州的研究结果不同，我们的目的是调查这两个地区精神分裂症与城市化之间的关系，以确定哪些因素可能影响这种关系。
我们使用了西澳大利亚州（ = 428784）和丹麦（ = 1357874）的基于人群的活产儿童队列。根据母亲在出生时居住地的城市化水平对儿童进行分类，并随访至 2015 年 6 月 30 日。与州级登记册的链接提供了精神分裂症诊断和一系列协变量的信息。使用 Cox 比例风险模型估计每个城市化类别中被诊断患有精神分裂症的比例，该模型调整了协变量。
在随访期间，西澳大利亚州有 1618 名（0.4%）儿童和丹麦有 11875 名（0.9%）儿童被诊断患有精神分裂症。在西澳大利亚州，与那些出生在最城市化地区的人相比，出生在最偏远地区的人没有经历较低的精神分裂症发病率（风险比 = 1.02 [95%置信区间：0.81，1.29]），而不是他们的丹麦同龄人（风险比 = 0.62 [95%置信区间：0.58，0.66]）。然而，当将西澳大利亚州的队列限制为非土著原住民的儿童时，结果与丹麦的发现一致（风险比 = 0.46 [95%置信区间：0.29，0.72]）。
我们的研究强调了弱势亚群可能掩盖与城市相关的风险因素对精神分裂症风险的贡献，以及在这种情况下进行分层分析的重要性。
