Prevalence and Spatial Distribution of Chronic Respiratory Diseases in Dar es Salaam, Tanzania: Hydrological and Household Influences

Chronic Respiratory Diseases (CRDs) are a major global health burden, causing significant mortality and morbidity. The World Health Organization reports CRDs led to 4.1 million deaths in 2023, affecting 454.6 million people (5.54% globally). While tobacco smoking is the leading risk factor, others include air pollution, occupational hazards, childhood respiratory infections, and genetic predisposition. This study examines hydrology's role in CRD prevalence and spatial distribution, alongside household-level factors. Using remote sensing, the Topographical Wetness Index (TWI) was calculated at 30 m resolution and linked to CRD prevalence data from 1,533 households across 15 income-stratified neighborhoods in Dar es Salaam, Tanzania. Generalized linear mixed models, geovalidation, and ground truthing were employed for analysis. Results showed that CRD prevalence was significantly associated with higher TWI scores (OR = 1.18 [1.04, 1.33] per TWI unit increase, p = 0.009), with flood-prone areas (TWI ≥ 15) exhibiting a ninefold greater risk (OR = 8.63 [2.13, 35]). Other independent risk factors included household size (OR = 1.15 [1.05, 1.25] per person, p = 0.003) and communal skip bin use (OR = 4.04 [1.04, 15.80], p = 0.045). Conversely, air conditioning reduced CRD risk (OR = 0.22 [0.06, 0.77], p = 0.017). Notably, neighborhood income was not directly associated with CRD prevalence after adjusting for other factors, indicating poverty acts as an indirect, rather than proximal, determinant. These findings link moist, mold-prone environments to CRD risk, especially in urbanizing cities. Poor households often settle in flood-prone areas due to affordability, underscoring hydrology's role in CRD disparities.