A time series analysis of weather variables and all-cause mortality in the Kasena-Nankana Districts of Northern Ghana, 1995–2010

Abstract

Introduction : Climate and weather variability can have significant health consequences of increased morbidity and mortality. However, today the impact of climate and weather variability, and consequentially, of climate change on population health in sub-Saharan Africa is not well understood. In this study, we assessed the association of daily temperature and precipitation with daily mortality by age and sex groups in Northern Ghana.

Methods : We analysed daily mortality and weather data from 1995 to 2010. We adopted a time-series Poisson regression approach to examine the short-term association of daily mean temperature and daily mean precipitation with daily mortality. We included time factors and daily lagged weather predictors and considered autocorrelation.

Results : For all populations, a statistically significant association of mean daily temperature with mortality at lag days 0–1 was observed below and above the 25th (27.48°C) and 75th (30.68°C) percentiles (0.19%; 95% confidence interval CI: 0.05%, 0.21%) and (1.14%; 95% CI: 0.12%, 1.54%), respectively. We also observed a statistically significant association of mean daily temperature above 75th percentile at lag days 2–6 and lag days 7–13 (0.32%; 95% CI: 0.16%, 0.25%) and 0.31% [95% CI: 0.14%, 0.26%]), respectively. A 10 mm increase in precipitation was associated with a 1.71% (95% CI: 0.10%, 3.34.9%) increase in mortality for all ages and sex groups at lag days 2–6. Similar results were also observed at lag days 2–6 and 14–27 for males, 2.92% (95% CI: 0.80%, 5.09%) and 2.35% (95% CI: 0.28%, 4.45%).

Conclusion : Short-term weather variability is strongly associated with mortality in Northern Ghana. The associations appear to differ among different age and sex groups. The elderly and young children were found to be more susceptible to short-term temperature-related mortality. The association of precipitation with mortality is more pronounced at the short-term for all age and sex groups and in the medium short-term among males. Reducing exposure to extreme temperature, particularly among the elderly and young children, should reduce the number of daily deaths attributable to weather-related mortality.

• mortality
• temperature
• precipitation
• time series analysis
• distributed lag model
• season

Acknowledgements

We wish to acknowledge the untiring efforts and commitment of the NHDSS field staff, data entry clerks and data managers in collecting and managing this longitudinal data. We express our profound gratitude to the NHDSS research community for their continual cordial relationship and support for the research work. We are most grateful to the staff of Navrongo Meteorological Station for their willingness to share the weather data with us to undertake this study. We are very grateful to all our sponsors who have supported and continue to support the NHDSS, particularly the Rockefeller Foundation, which supported the NHDSS in its maiden years of operation.

This research was supported by the INDEPTH Network. We thank Joacim Rocklöv, Yazoume Ye, Rainer Sauerborn, Sari Kovats, David Hondula and Martin Bangha who facilitated at INDEPTH workshops in Nouna, Burkina Faso and Accra Ghana, for the production of this work.

Notes

¹In 2008, a new district, Kassena-NankanaWest District, was carved out of the initial Kassena-Nankana District. Consequently, the NDSS now covers two districts.