Burden of Obstructive Lung Disease Follow-up in low/middle income countries (BOLD II)

慢性肺病是世界上最常见的死亡原因之一，在低收入国家尤为严重。尽管如此，关于这一主题的研究很少，在低收入国家几乎没有使用足够的质量保证来测量肺功能的研究。这项基线的BOLD研究测量了肺功能，并收集了36个国家44个地点的3.1万多人的背景、暴露、症状、生活质量和治疗信息。到目前为止，研究结果表明，这些国家(以及高收入国家)对慢性肺部疾病的许多假设可能是错误的。仅凭呼吸道狭窄(阻塞性肺活量测定法)不能解释这些疾病在低收入环境下估计的高死亡率。将高死亡率归因于慢性肺部疾病的一个更可能的解释是肺较小(限制性肺活量测定法)。在过去的半个世纪里，这种肺功能模式在很大程度上被忽视了，但在美国观察到了肺容量低的人的高死亡率，这可以解释为什么非裔美国人的死亡率更高，他们的肺平均也比美国白人小。尽管目前没有直接证据证明这一点，但这似乎是南亚、东南亚和撒哈拉以南非洲有记录的COPD死亡率高的最有可能的解释。然而，了解情况是否如此，对于决定未来研究和未来卫生政策的重点至关重要，因为阻塞性和限制性疾病具有不同的风险因素，需要不同的预防和治疗策略。这项提案将对15个低收入或中等收入国家20个地点的15,000人进行跟踪调查，将回答四个重要问题。首先，慢性呼吸系统疾病的高死亡率在多大程度上与狭窄的呼吸道(阻塞性疾病)或小的肺部(限制性疾病)有关。第二，在较贫穷国家的老年人中发现的低肺功能水平在多大程度上是由于他们早年生活中从未恢复的变化，还是他们的肺功能在以后的生活中继续下降得更快。第三，低收入国家的肺功能较差的人是否死于呼吸衰竭，或者死亡风险的增加是否也是由于心脏病和相关问题的死亡率较高，就像较富裕国家的情况一样。最后，这项研究将调查一些可能的风险因素，我们认为这些因素对于确定低收入国家的肺部健康是重要的，特别是关注饮食和接触不受监管的行业。尽管到目前为止，吸烟是导致呼吸道慢性阻塞的最重要的危险因素，但有些国家接触的烟草很少，但仍存在严重的呼吸道疾病问题。已经提出的其他风险因素，如烹饪火灾产生的烟雾，似乎无法解释这种差异。通过以高度标准化的方式收集更详细的信息，并通过调查这些因素和其他风险因素对它们如何影响随时间推移的肺功能下降速度的影响，我们将能够显著提高我们解释我们在早期研究中发现的关联(有时是缺乏关联)的能力。这项研究涵盖了东亚、南亚、中亚、北非、撒哈拉以南非洲和加勒比海地区的各种环境和人口。所有这些中心都表明，它们能够收集高质量的数据，伦敦国家心肺研究所的协调中心在管理大型国际肺部疾病研究方面有着悠久的历史。一个国际顾问委员会将有助于优化成果的传播。

Chronic lung disease is one of the most common causes of death in the world and is particularly high in low income countries. In spite of this there is very little research on the subject and almost none in low income countries that uses adequate quality assurance for the measurements of lung function. The baseline BOLD study measured lung function and collected information on the background, exposures, symptoms, quality of life and treatment of more than 31,000 people in 44 sites in 36 countries.The results of the study so far have shown that many of the assumptions that have been made about chronic lung disease in these countries (and in high income countries also) may be wrong. The prevalence of narrowing of the airways (obstructive spirometry) alone does not explain the high mortality estimated for these diseases in low income settings. A more likely explanation for the high mortality ascribed to chronic lung disease is the smaller size of lungs (restrictive spirometry). This pattern of lung function has largely been ignored for the last half century but a high mortality in those with low lung volumes has been observed in the United States and can explain the higher mortality seen in African Americans who also have smaller lungs on average than white Americans. Although there is no direct evidence for this at the current time, this seems to be the most likely explanation for the high recorded mortality from COPD in South Asia, South-East Asia and Sub-Saharan Africa. Understanding whether this is the case or not is, however, critical for deciding the emphasis of future research and future health policy as obstructive and restrictive diseases have different risk factors and will require different preventive and treatment strategies.This proposal, which will follow up 15,000 people in 20 sites in 15 low or middle income countries, will answer four important questions. First, how far the high mortality from Chronic Respiratory Disease is associated with narrow airways (obstructive disease) or small lungs (restrictive disease). Second how far the low level of lung function found in older people in poorer countries is due to changes in early life that they have never recovered from, or whether their lung function continues to decline more rapidly in later life. Third whether people with poor lung function in low income countries die from respiratory failure or whether the increased risk of death is also due to a higher mortality from heart disease and related problems, as seems to be the case in richer countries. Finally the study will investigate a number of possible risk factors that we believe are important for determining lung health in low income countries focussing particularly on diet and exposure to unregulated industries. Although smoking is by far the most important risk factor for chronic obstruction of the airways there are countries that have been exposed to very little tobacco and yet still have substantial problems with respiratory disease. Other risk factors that have been suggested such as smoke from cooking fires do not seem to explain this discrepancy. By collecting more detailed information in a highly standardised way and by investigating the effects of these and other risk factors on how they influence the rate of decline in lung function over time we will be able to improve considerably our ability to interpret the associations (and sometimes the lack of associations) that we have found in the earlier study.The centres included in this study cover a wide variety of environments and populations in East Asia, South Asia, Central Asia, North Africa, Sub-Saharan Africa and the Caribbean. All of the centres have shown that they are able to collect high quality data, and the co-ordinating centre at the National Heart and Lung Institute in London has a long history of managing large international studies of lung disease. An international advisory board will help to optimise dissemination of results.