PhD Thesis Presentation - Epidemiological assessment of multifactorial environmental exposures on respiratory health outcomes among young adults in Hong Kong

Respiratory diseases, both infectious and chronic, remain a major global burden, driven by population growth, aging, and environmental exposures, contributing to millions of deaths and disability-adjusted life years annually. Young adults, a systematically neglected group, face cumulative environmental risks during a critical developmental window of their life; therefore, the impact on the respiratory health requires detailed investigation. This study presents a multi-component investigation examining the multifactorial environmental determinants of respiratory health.

First, a systematic review and meta-analysis quantify the global association between ambient air pollutants and influenza-like illness. Second, this study conducts a secondary data analysis of COVID-19 from 2020 to 2021 in Hong Kong, evaluating the effects of ambient air pollutants, housing characteristics, and socio-demographic factors on COVID-19. Third, a cross-sectional survey of 1,139 university students assesses the associations of multifactorial exposures, including demographics, housing conditions, medical history, family history, ambient pollutants, lifestyle behaviours (tobacco smoke, electronic cigarettes, water-pipe smoking), and environmental tobacco smoke exposure with acute and chronic respiratory outcomes among young adults.

Meta-analysis showed that PM₂.₅, SO₂, and NO₂ were associated with higher risk of influenza-like illness. Multitude of factors related to estate, buildings, ambient pollutants, and weather influenced COVID-19 incidence. Primary survey data indicates; smoking behaviour (tobacco smoke use, electronic cigarettes, water-pipe smoking), pollutants, and housing characteristics are potential risk factors of respiratory symptoms.

By integrating environmental, lifestyle behaviour, and housing data, this epidemiological study addresses critical gaps in understanding how multiple exposures collectively shape respiratory disease risk. This research enhances our understanding of the detrimental effects of multi-exposure on respiratory morbidity in young adults and their long-term health consequences. Study findings call for targeted policy and research interventions and longitudinal research on improved housing standards, air quality policies, and smoking cessation programmes, to reduce the respiratory disease burden among young adults in urban settings.