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Multilevel Analysis of Trachomatous Trichiasis and Corneal Opacity in Nigeria: The Role of Environmental and Climatic Risk Factors on the Distribution of Disease.

Smith JL, Sivasubramaniam S, Rabiu MM, Kyari F, Solomon AW, Gilbert C - PLoS Negl Trop Dis (2015)

Bottom Line: The risk of TT/CO was associated with factors at both the individual and cluster levels, with approximately 14% of the total variation attributed to the cluster level.Beyond established individual risk factors (age, gender and occupation), there was strong evidence that environmental/climatic factors at the cluster-level (lower precipitation, higher land surface temperature, higher mean annual temperature and rural classification) were also associated with a greater risk of TT/CO.This study establishes the importance of large-scale risk factors in the geographical distribution of TT/CO in Nigeria, supporting anecdotal evidence that environmental conditions are associated with increased risk in this context and highlighting their potential use in improving estimates of disease burden at large scales.

View Article: PubMed Central - PubMed

Affiliation: Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom; Global Health Group, University of California San Francisco, San Francisco, California, United States of America.

ABSTRACT
The distribution of trachoma in Nigeria is spatially heterogeneous, with large-scale trends observed across the country and more local variation within areas. Relative contributions of individual and cluster-level risk factors to the geographic distribution of disease remain largely unknown. The primary aim of this analysis is to assess the relationship between climatic factors and trachomatous trichiasis (TT) and/or corneal opacity (CO) due to trachoma in Nigeria, while accounting for the effects of individual risk factors and spatial correlation. In addition, we explore the relative importance of variation in the risk of trichiasis and/or corneal opacity (TT/CO) at different levels. Data from the 2007 National Blindness and Visual Impairment Survey were used for this analysis, which included a nationally representative sample of adults aged 40 years and above. Complete data were available from 304 clusters selected using a multi-stage stratified cluster-random sampling strategy. All participants (13,543 individuals) were interviewed and examined by an ophthalmologist for the presence or absence of TT and CO. In addition to field-collected data, remotely sensed climatic data were extracted for each cluster and used to fit Bayesian hierarchical logistic models to disease outcome. The risk of TT/CO was associated with factors at both the individual and cluster levels, with approximately 14% of the total variation attributed to the cluster level. Beyond established individual risk factors (age, gender and occupation), there was strong evidence that environmental/climatic factors at the cluster-level (lower precipitation, higher land surface temperature, higher mean annual temperature and rural classification) were also associated with a greater risk of TT/CO. This study establishes the importance of large-scale risk factors in the geographical distribution of TT/CO in Nigeria, supporting anecdotal evidence that environmental conditions are associated with increased risk in this context and highlighting their potential use in improving estimates of disease burden at large scales.

No MeSH data available.


Related in: MedlinePlus

Prevalence of trichiasis (TT) or corneal opacity (CO) in adults over 40 years in Nigeria, 2005–2007.Higher prevalence clusters are predominantly in northern areas of Nigeria.
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pntd.0003826.g001: Prevalence of trichiasis (TT) or corneal opacity (CO) in adults over 40 years in Nigeria, 2005–2007.Higher prevalence clusters are predominantly in northern areas of Nigeria.

Mentions: Complete geolocated survey data were available for 304 clusters, from which 13,543 individuals aged 40 years and above, resident in 8,621 households, were examined for TT and CO. Overall, 198 (adjusted prevalence: 1.45%) individuals were diagnosed with either TT or CO in at least one eye, and only two individuals had clinical signs of CO without concurrent TT. Fig 1 presents the distribution of TT/CO among adults aged 40 years and above within clusters (prevalence ranging from 0 to 28.9%) and highlights the greater burden of trachoma in the northern areas of Nigeria.


Multilevel Analysis of Trachomatous Trichiasis and Corneal Opacity in Nigeria: The Role of Environmental and Climatic Risk Factors on the Distribution of Disease.

Smith JL, Sivasubramaniam S, Rabiu MM, Kyari F, Solomon AW, Gilbert C - PLoS Negl Trop Dis (2015)

Prevalence of trichiasis (TT) or corneal opacity (CO) in adults over 40 years in Nigeria, 2005–2007.Higher prevalence clusters are predominantly in northern areas of Nigeria.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4519340&req=5

pntd.0003826.g001: Prevalence of trichiasis (TT) or corneal opacity (CO) in adults over 40 years in Nigeria, 2005–2007.Higher prevalence clusters are predominantly in northern areas of Nigeria.
Mentions: Complete geolocated survey data were available for 304 clusters, from which 13,543 individuals aged 40 years and above, resident in 8,621 households, were examined for TT and CO. Overall, 198 (adjusted prevalence: 1.45%) individuals were diagnosed with either TT or CO in at least one eye, and only two individuals had clinical signs of CO without concurrent TT. Fig 1 presents the distribution of TT/CO among adults aged 40 years and above within clusters (prevalence ranging from 0 to 28.9%) and highlights the greater burden of trachoma in the northern areas of Nigeria.

Bottom Line: The risk of TT/CO was associated with factors at both the individual and cluster levels, with approximately 14% of the total variation attributed to the cluster level.Beyond established individual risk factors (age, gender and occupation), there was strong evidence that environmental/climatic factors at the cluster-level (lower precipitation, higher land surface temperature, higher mean annual temperature and rural classification) were also associated with a greater risk of TT/CO.This study establishes the importance of large-scale risk factors in the geographical distribution of TT/CO in Nigeria, supporting anecdotal evidence that environmental conditions are associated with increased risk in this context and highlighting their potential use in improving estimates of disease burden at large scales.

View Article: PubMed Central - PubMed

Affiliation: Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom; Global Health Group, University of California San Francisco, San Francisco, California, United States of America.

ABSTRACT
The distribution of trachoma in Nigeria is spatially heterogeneous, with large-scale trends observed across the country and more local variation within areas. Relative contributions of individual and cluster-level risk factors to the geographic distribution of disease remain largely unknown. The primary aim of this analysis is to assess the relationship between climatic factors and trachomatous trichiasis (TT) and/or corneal opacity (CO) due to trachoma in Nigeria, while accounting for the effects of individual risk factors and spatial correlation. In addition, we explore the relative importance of variation in the risk of trichiasis and/or corneal opacity (TT/CO) at different levels. Data from the 2007 National Blindness and Visual Impairment Survey were used for this analysis, which included a nationally representative sample of adults aged 40 years and above. Complete data were available from 304 clusters selected using a multi-stage stratified cluster-random sampling strategy. All participants (13,543 individuals) were interviewed and examined by an ophthalmologist for the presence or absence of TT and CO. In addition to field-collected data, remotely sensed climatic data were extracted for each cluster and used to fit Bayesian hierarchical logistic models to disease outcome. The risk of TT/CO was associated with factors at both the individual and cluster levels, with approximately 14% of the total variation attributed to the cluster level. Beyond established individual risk factors (age, gender and occupation), there was strong evidence that environmental/climatic factors at the cluster-level (lower precipitation, higher land surface temperature, higher mean annual temperature and rural classification) were also associated with a greater risk of TT/CO. This study establishes the importance of large-scale risk factors in the geographical distribution of TT/CO in Nigeria, supporting anecdotal evidence that environmental conditions are associated with increased risk in this context and highlighting their potential use in improving estimates of disease burden at large scales.

No MeSH data available.


Related in: MedlinePlus