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Time-series analysis of weather and mortality patterns in Nairobi's informal settlements
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
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2012 (English)In: Global health action, ISSN 1654-9880, Vol. 5, 23-32 p.Article in journal (Refereed) Published
Abstract [en]

Background: Many studies have established a link between weather (primarily temperature) and daily mortality in developed countries. However, little is known about this relationship in urban populations in sub-Saharan Africa. Objectives: The objective of this study was to describe the relationship between daily weather and mortality in Nairobi, Kenya, and to evaluate this relationship with regard to cause of death, age, and sex. Methods: We utilized mortality data from the Nairobi Urban Health and Demographic Surveillance System and applied time-series models to study the relationship between daily weather and mortality for a population of approximately 60,000 during the period 2003-2008. We used a distributed lag approach to model the delayed effect of weather on mortality, stratified by cause of death, age, and sex. Results: Increasing temperatures (above 75th percentile) were significantly associated with mortality in children and non-communicable disease (NCD) deaths. We found all-cause mortality of shorter lag of same day and previous day to increase by 3.0% for a 1 degree decrease from the 25th percentile of 18 degrees C (not statistically significant). Mortality among people aged 50+ and children aged below 5 years appeared most susceptible to cold compared to other age groups. Rainfall, in the lag period of 0-29 days, increased all-cause mortality in general, but was found strongest related to mortality among females. Low temperatures were associated with deaths due to acute infections, whereas rainfall was associated with all-cause pneumonia and NCD deaths. Conclusions: Increases in mortality were associated with both hot and cold weather as well as rainfall in Nairobi, but the relationship differed with regard to age, sex, and cause of death. Our findings indicate that weather-related mortality is a public health concern for the population in the informal settlements of Nairobi, Kenya, especially if current trends in climate change continue.

Place, publisher, year, edition, pages
2012. Vol. 5, 23-32 p.
Keyword [en]
time-series, temperature, rainfall, mortality, climate, urban
National Category
Public Health, Global Health, Social Medicine and Epidemiology
URN: urn:nbn:se:umu:diva-63044DOI: 10.3402/gha.v5i0.19065ISI: 000311724400001OAI: diva2:580877
Available from: 2012-12-27 Created: 2012-12-27 Last updated: 2015-08-19Bibliographically approved
In thesis
1. Making visible the invisible: Health risks from environmental exposures among socially deprived populations of Nairobi, Kenya
Open this publication in new window or tab >>Making visible the invisible: Health risks from environmental exposures among socially deprived populations of Nairobi, Kenya
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Most countries of sub-Saharan Africa (SSA) are experiencing a high rate of ur­banization accompanied with unplanned development resulting into sprawl of slums. The weath­er patterns and air pollution sources in most urban areas are changing with significant effects on health. Studies have established a link between environmental exposures, such as weather variation and air pollution, and adverse health outcomes. However, little is known about this relationship in urban populations of SSA where more than half the population reside in slums, or slum like conditions. A major reason for this is the lack of systematic collection of data on exposure and health outcomes. High quality prospective data collection and census registers still remain a great challenge. However, within small and spatially defined areas, dynamic cohorts have been established with continuous monitoring of health outcomes. Collection of environmental exposure data can complement cohort studies to investigate health effects in relation to environmental exposures. The objective of this research was to study the health effects of selected environmental exposure among the urban poor population in Nairobi, Kenya.

Methods: We used the platform of the Nairobi Urban Health and Demographic Surveillance System (NUHDSS), including two nested research studies, to provide data on mortality and mor­bidity. The NUHDSS was established in two areas of Nairobi, Korogocho and Viwandani, in 2003 and provides a unique opportunity for access to longitudinal population data. In addition, we conducted real-time measurements of particulate matter (PM2.5) in the areas from February to October in 2013. We obtained meteorological measurements from the Moi Air Base and Nairobi airport weather stations for the study period. We also conducted a cross-sectional survey to estab­lish the communities’ perceptions about air pollution and its related health risks. Time series re­gression models with a distributed lag approach were used to model the relationship between weather and mortality. A semi-ecological study with group level exposure assignment to individuals was used to assess the relationship between child health (morbidity and mortality) and the extent of PM2.5 exposure.

Results: There was a significant association between daily mean temperature and all-cause mor­tality with minimum mortality temperature (MMT) in the range of 18 to 20 °C. Both mortality risk and years of life lost analysis showed risk increases in relation to cold temperatures, with pronounced effect among children under-five. Overall, mortality risks were found to be high during cold periods of the year, rising with lower temperature from MMT to about 40% in the 0–4 age group, and by about v 20% among all ages. The results from air pollution assessment showed high levels of PM2.5 concentration exceeding World Health Organization (WHO) guideline limits in the two study ar­eas. The air pollution concentration showed similar seasonal and diurnal variation in the two slums. The majority of community residents reported to be exposed to air pollution at work, with 66% reporting to be exposed to different sources of air pollution. Despite the observed high level of exposure, residents had poor perception of air pollution levels and associated health risks. Children in the high-pollution areas (PM2.5≥ 25 μg⁄m3) were at significantly higher risk for morbidity (OR = 1.30, 95% CI: 1.13-1.48) and cough as the only form of morbidity (OR = 1.33, 95% CI: 1.15-1.53) compared to those in low-pollution areas. In addition, exposure to high levels of pollution was associated with high child mortality from all-causes (IRR=1.15, 95% CI: 1.03-1.28), and indicated a positive association to respiratory related mortality (IRR=1.10, 95% CI: 0.91-1.33).

Conclusion: The study findings extend our knowledge on health impacts related to environmental exposure by providing novel evidence on the risks in disadvantaged urban populations in Af­rica. More specifically, the study illustrates the invisible health burden that the urban poor population are facing in relation to weather and air pollution exposures. The effect of cold on population is preventable. This is manifested by the effective adaptation to cold conditions in high-latitude Nordic countries by housing standards and clothing, as well as a well-functioning health system. Further, awareness and knowledge of consequences, and reductions in exposure to air pollution, are necessary to improve public health in the slum areas. In conclusion, adverse health impacts caused by environmental stressors are critical to assess further in disadvantaged populations, and should be followed by development of mitigation measures leading to improved health and well being in SSA.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2015. 60 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1734
air pollution, urban health, temperature-related mortality, particulate matter, exposure assessment, child health
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Research subject
Epidemiology; Public health
urn:nbn:se:umu:diva-106857 (URN)978-91-7601-306-9 (ISBN)
Public defence
2015-09-11, Sal 135, Allmänmedicin, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Available from: 2015-08-21 Created: 2015-08-11 Last updated: 2015-08-21Bibliographically approved

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