Introduction

Urban greening is a climate change-related policy with considerable health benefits. But do these benefits extend to prevention of dementia and, if so, which types of green space matter?

Method

Multilevel discrete time-to-event cohort study of incident Alzheimer’s disease over 11 years among a baseline recruited between January 1, 2006 and December 31, 2009 (the Sax Institute’s 45 and Up Study). Sampled participants for this study (N=109,688) were aged 45 years or older with no record of dementia up to 6 years before baseline, living in the cities of Sydney, Wollongong and Newcastle, Australia. Exposures were percentage total green space, tree canopy and open grass within 1.6-km road network distance buffers at baseline. Outcomes were time-to-first anti-dementia medication prescription (Department of Human Services) or dementia detected during hospitalisation or death up to 31 December 2016 (up to 11 years follow-up). Outcomes were analysed in parallel to triangulate on associations with green space, while testing for bias due to potential under-prescribing of anti-dementia medications. Models were adjusted for baseline person-level factors and area-level socioeconomic disadvantage.

Results

Dementia detection varied by case ascertainment method. 1.55% (1,703/109,688) persons were detected using prescribed anti-dementia medications. 3.32% (3,639/109,688) persons were detected during hospitalisation or death via ICD-10 codes. Dementia incidence irrespective of outcome measurement was lower among females, younger participants, those living in couples, with higher qualifications and higher incomes. Dementia risk was lower with more tree canopy when the outcome was measured using hospital and death records (≥30% vs <10% tree canopy incidence hazard ratio (IHR) = 0.86, 95%CI 0.75, 0.99), after adjusting for person-level factors. The opposite association was observed when anti-dementia medications were used to detect dementia (≥30% vs <10% tree canopy IHR = 1.33, 95%CI 1.07, 1.66). Anti-dementia medication-based detection also indicated lower dementia risk with more open grass (≥20% vs <5% IHR = 0.83, 95%CI 0.67, 1.03). Anti-dementia medication prescribing was lower in the highest vs. lowest area-level disadvantage tertile (29.8% vs. 43.7%) among people diagnosed with dementia, indicating potential bias from geographic differences in prescribing practices. Adjusting for area-level disadvantage explained associations between tree canopy, open grass and dementia when detected by anti-dementia medication, but had negligible impact on negative (i.e. potentially protective) association between tree canopy and dementia detected by hospital and death records (≥30% vs <10% tree canopy hazard ratio 0.84, 95%CI 0.72, 0.99).

Conclusions

Increasing urban tree canopy cover may help to reduce the risk of dementia. Replication in contrasting contexts and mediation studies to assess pathways are warranted.

中文翻译：

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109,688名澳大利亚人队列中的城市绿地，树冠和11年痴呆症风险

介绍

城市绿化是一项与气候变化有关的政策，具有很大的健康益处。但是，这些好处是否可以扩展到预防痴呆症？如果是的话，哪种类型的绿色空间很重要？

方法

在2006年1月1日至2009年12月31日之间募集的基线中，针对11年内发生的阿尔茨海默氏病的多水平离散事件队列研究（Sax Institute的45岁及以上研究）。这项研究的样本参与者（N = 109,688）年龄在45岁或以上，在基线之前的6年内没有痴呆症记录，居住在澳大利亚悉尼，伍伦贡和纽卡斯尔等城市。暴露量是基线处1.6公里道路网络距离缓冲区内的总绿地，树冠和开阔草地的百分比。结果是直至2016年12月31日（最多随访11年）在住院或死亡期间首次发现抗痴呆药物处方（人类服务部）或痴呆。同时对结果进行了分析，以对与绿色空间的关联进行三角测量，同时测试由于抗痴呆药物的潜在处方不足而引起的偏见。针对基线人员水平因素和地区水平的社会经济劣势对模型进行了调整。

结果

痴呆症的检测因病例确定方法而异。使用处方的抗痴呆药检出1.55％（1,703 / 109,688）人。通过ICD-10代码在住院或死亡期间发现了3.32％（3,639 / 109,688）人。女性，较年轻的参与者，成对的夫妇，具有较高的资格和较高的收入，无论采用何种结局衡量，痴呆的发生率均较低。根据患者和医院的死亡记录对结局进行测量后，痴呆风险较低，树冠较多（≥30％vs <10％树冠发生风险比（IHR）= 0.86，95％CI 0.75，0.99），水平因素。当使用抗痴呆药物检测痴呆时，观察到相反的关联（≥30％vs <10％树冠层IHR = 1.33，95％CI 1.07，1.66）。以抗痴呆药物为基础的检测还表明，开阔草地可以降低痴呆风险（≥20％vs <5％IHR = 0.83，95％CI 0.67，1.03）。在被诊断为痴呆症的人群中，抗痴呆药物处方的最高和最低区域三分位数的比例较低（分别为29.8％和43.7％），表明处方方法的地域差异可能存在偏见。调整区域水平的不利因素后，解释了用抗痴呆药物检测到的树冠，开阔的草地和痴呆之间的关联，但是对医院检测到的树冠和痴呆之间的负面（即潜在的保护性）关联以及死亡记录（≥30）的影响微不足道％与<10％的树冠危害比0.84，95％CI 0.72，0.99）。在被诊断为痴呆症的人群中，抗痴呆药物处方的最高和最低区域三分位数的比例较低（分别为29.8％和43.7％），表明处方方法的地域差异可能存在偏见。调整区域水平的不利因素后，解释了用抗痴呆药物检测到的树冠，开阔的草地和痴呆之间的关联，但是对医院检测到的树冠和痴呆之间的负面（即潜在的保护性）关联以及死亡记录（≥30）的影响微不足道％与<10％的树冠危害比0.84，95％CI 0.72，0.99）。在被诊断为痴呆症的人群中，抗痴呆药物处方的最高和最低区域三分位数的比例较低（分别为29.8％和43.7％），表明处方方法的地域差异可能存在偏见。调整区域水平的不利因素后，解释了用抗痴呆药物检测到的树冠，开阔的草地和痴呆之间的关联，但是对医院检测到的树冠和痴呆之间的负面（即潜在的保护性）关联以及死亡记录（≥30）的影响微不足道％与<10％的树冠危害比0.84，95％CI 0.72，0.99）。

结论

增加城市树冠覆盖率可能有助于降低痴呆症的风险。在相反的情况下进行复制和进行中介研究以评估途径是必要的。