As the leading cause of death in the United States, managing coronary heart disease (CHD) is not only a critical objective of the health care system but also a source of resource utilization. With the United States emitting a quarter of the world’s health care-related carbon footprint, the impact of health care access on travel-related carbon emissions must also be examined.^1,2 Thus, we investigated the transport-related carbon emissions for routine ambulatory care for CHD in the United States.

We obtained data on the crude prevalence (%) of CHD (patients aged ≥18 years) from the Centers for Disease Control PLACES database 2022. National Provider Identifier records from the National Plan and Provider Enumeration System were obtained in July 2023. We identified cardiologists and their practice business addresses (geocoded to longitude and latitude). We calculated the Haversine distance between each census tract (CT) centroid (2010 census) and the nearest cardiologist. We obtained the estimated CO₂ emissions from a typical passenger vehicle from the Environmental Protection Agency: tailpipe CO₂ emission of 248.55 g per km, based on a fuel consumption of 1 gallon per 35.73 km.³ CTs were considered urban if they had at least 2000 housing units or had a population of at least 5000 (Census Bureau). We obtained the 2018 social vulnerability index from the Agency for Toxic Substances and Disease Registry. The social vulnerability index is a measure that provides a relative indication of the vulnerability of CTs based on 16 social factors, with greater values indicating increased vulnerability.

We calculated the total CT tailgate CO₂ emissions in metric tons (MTCO2) for a round trip to the nearest cardiologist, referred to as CHD ambulatory care transport–related carbon footprint (ACT-CF) in this article, per year, calculated as follows:

The estimated number of individuals in a CT with CHD was obtained by multiplying the crude CHD prevalence (%) by the adult CT population. We reported the national estimate of the ACT-CF as the median and interquartile range (IQR), weighted by the number of individuals with CHD in the CT. We reported results separately for rural and urban CT and stratified our analysis by social vulnerability index quartiles. As a comparator, we estimated the total and national median emissions if the follow-up was provided by primary care providers (defined as internal medicine or family medicine specialty). We used R, version 4.3.0, for statistical analyses and maps. Due to the use of publicly available data, ethical approval was not required.

The ACT-CF was calculated and mapped for 13 381 715 patients with CHD in 69 328 CTs linked with 49 587 cardiologists in the contiguous United States (Figure [A]), totaling 63 005 MTCO2. Patients residing in urban CTs contributed 27 892 MTCO2 and rural CTs contributed 35 113 MTCO2. The national median ACT-CF was 0.42 MTCO2 (IQR, 0.17–1.31). For urban CTs (10 309 198 patients with CHD), median emissions were 0.29 MTCO2 (IQR, 0.13–0.61), while for rural residents (3 072 517 patients with CHD), it was 2.13 MTCO2 (IQR, 1.26–3.59). Figure (B) shows the median ACT-CF by social vulnerability index quartile according to urban and rural settings. In comparison, emissions would total 21 747 MTCO2, with a national median of 0.16 MTCO2 (IQR, 0.07–0.46) if patients had a similar number of visits with the nearest primary care provider.

Figure. Spatial and social disparities in estimated carbon footprint associated with coronary heart disease (CHD) patients’ travel to cardiologists. A, Map of the census tract-level tailpipe CO₂ emissions in metric tons (MTCO2) associated with patients with CHD traveling to the nearest cardiologists (CHD ambulatory care transport–related carbon footprint). B, CHD ambulatory care transport–related carbon footprint stratified by setting and according to social vulnerability index (SVI) quartiles.

We identified substantial heterogeneity between urban and rural emissions, with rural residents emitting ≈7.3× more tailpipe emissions than urban residents, likely due to longer commutes. The total ACT-CF for patients with CHD in the United States is equivalent to powering over 12 000 homes annually. To offset this carbon, over 75 000 acres of forest would be needed.³ As a result, possible measures to offset these carbon emissions must be envisioned. One strategy involves improving preventive care to reduce specialty health care visits. Additionally, communities with high levels of social vulnerability suffer from the paradox of poor access and yet needing higher acuity care. Recent advancements in telemedicine with televisits and home monitoring devices (eg, blood pressure) and even remote electrocardiography and ultrasonography may provide an avenue to improve health care access while reducing the environmental footprint of health care. While telemedicine usage may increase electricity consumption, this carbon footprint is much lower than that of transportation-related emissions.²

Typically, individuals in affluent areas with higher socioeconomic status emit more CO₂, due to higher consumption.⁴ However, our results demonstrate that patients in vulnerable and rural areas, given the longer distances to cardiovascular care, inevitably produce greater vehicle emissions owing to reduced geographic proximity to cardiologists. Additionally, rural socioeconomically disadvantaged populations may have higher CHD prevalence and morbidity compared with their urban counterparts, potentially leading to more frequent follow-up visits.⁵

In conclusion, ambulatory care for CHD in the United States is a considerable source of traffic-related greenhouse gas emissions particularly in rural areas with higher social vulnerability. Exploring responsible mitigation strategies to reduce these emissions, while ensuring adequate health care, must be a priority.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

None.

Nonstandard Abbreviations and Acronyms

ACT-CF	coronary heart disease ambulatory care transport–related carbon footprint
CT	census tract
IQR	interquartile range
MTCO2	CO2 emissions in metric tons

coronary heart disease ambulatory care transport–related carbon footprint

census tract

interquartile range

CO₂ emissions in metric tons

Disclosures None.

For Sources of Funding and Disclosures, see page 1220.

中文翻译：

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美国冠心病门诊护理与交通相关的碳足迹

作为美国主要的死亡原因，冠心病（CHD）的治疗不仅是医疗保健系统的一个重要目标，也是资源利用的一个来源。由于美国排放的与医疗保健相关的碳足迹占世界的四分之一，因此还必须研究医疗保健获取对与旅行相关的碳排放的影响。^1,2因此，我们调查了美国冠心病常规门诊护理中与交通相关的碳排放。

我们从 2022 年疾病控制中心 PLACES 数据库中获得了有关 CHD（年龄≥18 岁的患者）粗患病率 (%) 的数据。来自国家计划和提供者枚举系统的国家提供者标识符记录于 2023 年 7 月获得。我们确定了心脏病专家及其实践业务地址（地理编码为经度和纬度）。我们计算了每个人口普查区 (CT) 质心（2010 年人口普查）与最近的心脏病专家之间的半正矢距离。我们从环境保护局获得了典型乘用车的CO ₂排放量估算值：基于每 35.73 公里 1 加仑的燃油消耗，尾气 CO _{2排放量为每公里 248.55 克。} ³如果 CT 拥有至少 2000 个住房单元或人口至少 5000 人，则被视为城市（人口普查局）。我们从有毒物质和疾病登记局获得了 2018 年社会脆弱性指数。社会脆弱性指数是基于16个社会因素提供CT脆弱性相对指标的度量，值越大表明脆弱性越高。

_{我们计算了每年往返最近心脏病专家的 CT 尾门 CO 2}排放总量（以公吨为单位）（MTCO2），在本文中称为 CHD 门诊护理运输相关碳足迹 (ACT-CF)，计算如下:

CT 中患有 CHD 的估计人数是通过将粗 CHD 患病率 (%) 乘以成人 CT 人群得出的。我们将 ACT-CF 的全国估计值报告为中位数和四分位距 (IQR)，并根据 CT 中患有 CHD 的人数进行加权。我们分别报告了农村和城市 CT 的结果，并按社会脆弱性指数四分位数对我们的分析进行了分层。作为比较，如果初级保健提供者（定义为内科或家庭医学专业）提供后续服务，我们估计了总排放量和全国排放量中位数。我们使用 R 版本 4.3.0 进行统计分析和绘制地图。由于使用公开数据，因此不需要道德批准。

计算并绘制了 69 328 个 CT 中 13 381 715 名 CHD 患者的 ACT-CF，这些患者与美国本土的 49 587 名心脏病专家相关（图 [A]），总计 63 005 MTCO2。居住在城市CT的患者贡献了27 892 MTCO2，农村CT的患者贡献了35 113 MTCO2。全国 ACT-CF 中位数为 0.42 MTCO2（IQR，0.17-1.31）。对于城市CT（10 309 198名CHD患者），中位排放量为0.29 MTCO2（IQR，0.13-0.61），而对于农村居民（3 072 517名CHD患者），中位排放量为2.13 MTCO2（IQR，1.26-3.59）。图 (B) 显示了按城市和农村环境划分的社会脆弱性指数四分位的 ACT-CF 中位数。相比之下，如果患者就诊最近的初级保健提供者的次数相似，则排放总量将为 21 747 MTCO2，全国中位数为 0.16 MTCO2（IQR，0.07-0.46）。

数字。 与冠心病 (CHD) 患者去看心脏病专家相关的估计碳足迹的空间和社会差异。 A，与 CHD 患者前往最近的心脏病专家处相关的人口普查区尾气 CO ₂排放量（以公吨为单位） (MTCO2) 地图（CHD 门诊护理运输相关碳足迹）。B，根据社会脆弱性指数（SVI）四分位数设置并与 CHD 门诊护理运输相关的碳足迹进行分层。

我们发现城乡排放之间存在显着异质性，农村居民的尾气排放量比城市居民多约 7.3 倍，这可能是由于通勤时间更长。美国 CHD 患者的 ACT-CF 总量相当于每年为 12,000 多个家庭供电。为了抵消这种碳排放，需要超过 75,000 英亩的森林。³因此，必须设想抵消这些碳排放的可能措施。其中一项策略是改善预防性护理，以减少专科医疗就诊。此外，社会脆弱性较高的社区面临着医疗服务不畅却又需要更敏锐护理的矛盾。远程医疗的最新进展包括电视访问和家庭监测设备（例如血压），甚至远程心电图和超声检查，可以提供改善医疗保健可及性的途径，同时减少医疗保健的环境足迹。虽然远程医疗的使用可能会增加电力消耗，但这种碳足迹远低于交通相关的排放。²

通常，社会经济地位较高的富裕地区的个人由于较高的消费而排放更多的CO _{2 。} ⁴然而，我们的结果表明，脆弱地区和农村地区的患者由于距离心血管护理中心较远，由于与心脏病专家的地理距离较近，不可避免地会产生更多的车辆排放。此外，与城市人群相比，农村社会经济弱势群体的冠心病患病率和发病率可能更高，这可能导致更频繁的随访。⁵

总之，美国冠心病的门诊护理是交通相关温室气体排放的重要来源，特别是在社会脆弱性较高的农村地区。探索负责任的缓解策略以减少这些排放，同时确保充足的医疗保健，必须成为优先事项。

支持本研究结果的数据可根据合理要求从通讯作者处获得。

没有任何。

非标准缩写词和首字母缩略词

ACT-CF	冠心病门诊护理交通相关碳足迹
CT	人口普查区
IQR	四分位距
平均二氧化碳浓度	CO 2排放量（公吨）

冠心病门诊护理交通相关碳足迹

人口普查区

四分位距

CO ₂排放量（公吨）

披露无。

有关资金来源和披露信息，请参阅第 1220 页。