Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA.
Occup Environ Med. 2011 Feb;68(2):89-95. doi: 10.1136/oem.2009.048033. Epub 2010 Aug 25.
Cross-sectional studies have shown declines in lung function among refractory ceramic fibre (RCF) workers with increasing fibre exposure. This study followed current and former workers (n=1396) for up to 17 years and collected 5243 pulmonary function tests.
Cumulative fibre exposure and production years were categorised into exposure levels at five manufacturing locations. Conventional longitudinal models did not adequately partition age-related changes from other time-dependent variables. Therefore, a restricted cubic spline model was developed to account for the non-linear decline with age.
Cumulative fibre >60 fibre-months/cc showed a significant loss in lung function at the first test. When results were examined longitudinally, cumulative exposure was confounded with age as workers with the highest cumulative exposure were generally older. A longitudinal model adjusted by age groups was implemented to control for this confounding. No consistent longitudinal loss in lung function was observed with RCF exposure. Smoking, initial weight and weight increase were significant factors.
No consistent decline was observed longitudinally with exposure to RCF, although cross-sectional and longitudinal findings were discordant. Confounding and accelerated lung function declines with ageing and the correlation of multiple time-dependent variables should be considered in order to minimise error and maximise precision. An innovative statistical methodology for these types of data is described.
横断面研究表明，随着耐火陶瓷纤维（RCF）工人纤维暴露量的增加，其肺功能下降。本研究对 1396 名现职和离职工人进行了长达 17 年的随访，并收集了 5243 次肺功能检测数据。
将累计纤维暴露量和工龄分为五个生产地点的暴露水平。常规的纵向模型不能充分区分与年龄相关的变化和其他随时间变化的变量。因此，开发了受限立方样条模型来解释与年龄相关的非线性下降。
累积纤维>60 纤维-月/cc 在第一次检测时就显示出肺功能明显下降。当结果进行纵向分析时，累积暴露与年龄有关，因为累积暴露最高的工人通常年龄较大。为了控制这种混杂因素，实施了按年龄组调整的纵向模型。随着 RCF 暴露，肺功能没有持续的纵向下降。吸烟、初始体重和体重增加是显著的影响因素。
虽然横断面和纵向研究结果不一致，但纵向观察到的 RCF 暴露并没有一致的下降。应考虑混杂因素和与年龄相关的肺功能加速下降，以及多个随时间变化的变量之间的相关性，以尽量减少误差并最大限度地提高精度。本文描述了一种用于此类数据的创新统计方法。
