Life-course effects of air pollution (LEAP) on cardio-respiratory morbidity in the MRC National Survey of Health and Development
Creators: name: Al-Kanaani, Zaina Khalil Ibrahim
Publisher: name: Imperial College London
Year: 2014

description: Most of the epidemiological studies of long term exposure to air pollution showed increased risk of death from cardio-respiratory diseases. However the effect of long-term exposure to air pollution on morbidity is less clear. Additionally, questions as to which stage of life is more important in the effect of air pollution on health in adulthood are still unanswered. This project investigates the relationship between long-term exposure to air pollution and cardio-respiratory morbidity using the National Survey for Health and Development (NSHD) with consideration to lifestyle and socioeconomic factors. A comparison between early life and more recent exposures to air pollution will also be made. Finally, the effect of cumulative and change in air pollution over the life course will be explored. Lung function was measured and self-reported chronic bronchitis (CB) symptoms and ischaemic heart disease (IHD) were collected in 1989, 1999 and 2006/10 for more than 3000 participants. A residential history of the NSHD participants from 1962 onwards was constructed using addresses and/or postcodes and was geocoded and linked to model black smoke (BS) sulphur dioxide (SO2) in 1962, 1971, 1981 and 1991 and nitrogen dioxide (NO2) air pollution in 1991, 2001 and 2010-11. Earlier childhood exposures to air pollutants were assessed using the Douglas and Waller index. Relationships to air pollution were investigated using various statistical models. Contrary to expectations, some results suggested protective effects of air pollution on lung function and symptoms of CB. BS showed positive associations with lung function particularly from 1999 follow-up; 10 µg/m3 of BS in 1971 and 10 µg/m3 in 1991 were associated with 19.2ml (95%CI: 3.5-34.9) and 82.9ml (95%CI: 21.2-144.5) increase in Forced Vital Capacity (FVC) respectively. SO2 showed some positive (protective) associations; 10 µg/m3 of SO2 in 1962 was associated with 3.9 ml (95%CI: 0.1-7.9) increase in Forced Expiratory Volume in 1 second (FEV1) and 5.4 ml (95%CI: 0.2-10.7) increase in Forced Vital Capacity (FVC) in 1989. BS and SO2 both showed positive (protective) associations with lung function decline where 10 µg/m3 of BS in 1981 was associated with 80 ml (95%CI: 16-150) less decline in FVC ; and 10 µg/m3 of SO2 in 1991 was associated with 70 ml (95%CI: 22-120 ) less decline in FVC over the 20 year period. Change and cumulative BS did not show a clear pattern in generalized analyses, however results from stratified analyses suggested positive effects on men that indicate higher BS exposure was associated with better lung function. These protective effects were more consistently observed in SO2 analyses; 10 µg/m3 change (decrease) in SO2 between 1962 and 1991 was associated with 4.3ml (95%CI: 0.4-8.2) higher FEV1 in 1989, 6.1 ml (95%CI: 0.6-11.5) higher FVC in 1989, and 8.4ml (95% CI: 3.0-13.9) higher FVC in 1999. Higher cumulative exposure of 10 µg/m3 of SO2 was associated with 0.5 ml (95% CI: 0.1-0.9) increase in FVC in 1999. Air pollution was not associated with prevalence of CB, results indicated some protective effects. Air pollution was not associated with IHD prevalence; however detrimental effects were suggested. A healthy survivor effect would explain the findings for CB and lung function whereby the most exposed individuals who potentially experience more ill health are under-represented in the study and were differentially lost to follow up. Some evidence was found to suggest greater drop-out in individuals with higher exposure in more deprived areas. However, positive association between decline in air pollution and lung function may be related to the large falls in air pollution levels over the time period of study.