Mortality caused by influenza and respiratory syncytial virus by age group in England and Wales 1999–2010

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Abstract

Please cite this paper as: Hardelid et al. (2012) Mortality caused by influenza and respiratory syncytial virus by age group in England and Wales 1999–2010. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00345.x.

Background: The mortality burden caused by influenza cannot be quantified directly from death certificates because of under‐recording; therefore, the estimated number of influenza deaths has to be obtained through statistical modelling.

Objective: To estimate the number of deaths caused by influenza and respiratory syncytial virus (RSV) in England and Wales between 1999 and 2010 using a multivariable regression model.

Methods: Generalised linear models were used to estimate weekly deaths by age group (<15, 15–44, 45–74 and 75+ years) as a function of positive influenza and RSV isolates. Adjustment was made for temperature variation (using weekly means of daily Central England temperature time series), underlying seasonal variation and temporal trends. The parameters from the model were used to predict the number of deaths caused by influenza and RSV across winter seasons.

Results: Between 7000 and 25 000 deaths across all ages were associated with influenza in the winter periods 1999–2009. The mortality burden was the highest among the over 75 age group, among whom 2·5–8·1% of deaths were caused by influenza. The lowest number of influenza deaths was estimated for the winter 2009/2010 when pandemic influenza A/H1N1 (2009) was the predominant circulating strain. RSV accounted for 5000–7500 deaths each winter season.

Conclusions: The model presented provides a robust and reasonable approach to estimating the number of deaths caused by influenza and RSV by age group at the end of each winter.

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Most cited references 35

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Mortality associated with influenza and respiratory syncytial virus in the United States.

William W Thompson, David Shay (2003)

Influenza and respiratory syncytial virus (RSV) cause substantial morbidity and mortality. Statistical methods used to estimate deaths in the United States attributable to influenza have not accounted for RSV circulation. To develop a statistical model using national mortality and viral surveillance data to estimate annual influenza- and RSV-associated deaths in the United States, by age group, virus, and influenza type and subtype. Age-specific Poisson regression models using national viral surveillance data for the 1976-1977 through 1998-1999 seasons were used to estimate influenza-associated deaths. Influenza- and RSV-associated deaths were simultaneously estimated for the 1990-1991 through 1998-1999 seasons. Attributable deaths for 3 categories: underlying pneumonia and influenza, underlying respiratory and circulatory, and all causes. Annual estimates of influenza-associated deaths increased significantly between the 1976-1977 and 1998-1999 seasons for all 3 death categories (P<.001 for each category). For the 1990-1991 through 1998-1999 seasons, the greatest mean numbers of deaths were associated with influenza A(H3N2) viruses, followed by RSV, influenza B, and influenza A(H1N1). Influenza viruses and RSV, respectively, were associated with annual means (SD) of 8097 (3084) and 2707 (196) underlying pneumonia and influenza deaths, 36 155 (11 055) and 11 321 (668) underlying respiratory and circulatory deaths, and 51 203 (15 081) and 17 358 (1086) all-cause deaths. For underlying respiratory and circulatory deaths, 90% of influenza- and 78% of RSV-associated deaths occurred among persons aged 65 years or older. Influenza was associated with more deaths than RSV in all age groups except for children younger than 1 year. On average, influenza was associated with 3 times as many deaths as RSV. Mortality associated with both influenza and RSV circulation disproportionately affects elderly persons. Influenza deaths have increased substantially in the last 2 decades, in part because of aging of the population, underscoring the need for better prevention measures, including more effective vaccines and vaccination programs for elderly persons.

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Heat-related and cold-related deaths in England and Wales: who is at risk?

S Hajat, R S Kovats, K Lachowycz (2007)

Despite the high burden from exposure to both hot and cold weather each year in England and Wales, there has been relatively little investigation on who is most at risk, resulting in uncertainties in informing government interventions. To determine the subgroups of the population that are most vulnerable to heat-related and cold-related mortality. Ecological time-series study of daily mortality in all regions of England and Wales between 1993 and 2003, with postcode linkage of individual deaths to a UK database of all care and nursing homes, and 2001 UK census small-area indicators. A risk of mortality was observed for both heat and cold exposure in all regions, with the strongest heat effects in London and strongest cold effects in the Eastern region. For all regions, a mean relative risk of 1.03 (95% confidence interval (CI) 1.02 to 1.03) was estimated per degree increase above the heat threshold, defined as the 95th centile of the temperature distribution in each region, and 1.06 (95% CI 1.05 to 1.06) per degree decrease below the cold threshold (set at the 5th centile). Elderly people, particularly those in nursing and care homes, were most vulnerable. The greatest risk of heat mortality was observed for respiratory and external causes, and in women, which remained after control for age. Vulnerability to either heat or cold was not modified by deprivation, except in rural populations where cold effects were slightly stronger in more deprived areas. Interventions to reduce vulnerability to both hot and cold weather should target all elderly people. Specific interventions should also be developed for people in nursing and care homes as heat illness is easily preventable.

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International study of temperature, heat and urban mortality: the 'ISOTHURM' project.

Anthony J McMichael, Paul Wilkinson, R Sari Kovats … (2008)

This study describes heat- and cold-related mortality in 12 urban populations in low- and middle-income countries, thereby extending knowledge of how diverse populations, in non-OECD countries, respond to temperature extremes. The cities were: Delhi, Monterrey, Mexico City, Chiang Mai, Bangkok, Salvador, São Paulo, Santiago, Cape Town, Ljubljana, Bucharest and Sofia. For each city, daily mortality was examined in relation to ambient temperature using autoregressive Poisson models (2- to 5-year series) adjusted for season, relative humidity, air pollution, day of week and public holidays. Most cities showed a U-shaped temperature-mortality relationship, with clear evidence of increasing death rates at colder temperatures in all cities except Ljubljana, Salvador and Delhi and with increasing heat in all cities except Chiang Mai and Cape Town. Estimates of the temperature threshold below which cold-related mortality began to increase ranged from 15 degrees C to 29 degrees C; the threshold for heat-related deaths ranged from 16 degrees C to 31 degrees C. Heat thresholds were generally higher in cities with warmer climates, while cold thresholds were unrelated to climate. Urban populations, in diverse geographic settings, experience increases in mortality due to both high and low temperatures. The effects of heat and cold vary depending on climate and non-climate factors such as the population disease profile and age structure. Although such populations will undergo some adaptation to increasing temperatures, many are likely to have substantial vulnerability to climate change. Additional research is needed to elucidate vulnerability within populations.

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Author and article information

Journal

Journal ID (nlm-ta): Influenza Other Respir Viruses

Journal ID (iso-abbrev): Influenza Other Respir Viruses

Journal ID (doi): 10.1111/(ISSN)1750-2659

Journal ID (publisher-id): IRV

Title: Influenza and Other Respiratory Viruses

Publisher: Blackwell Publishing Ltd (Oxford, UK )

ISSN (Print): 1750-2640

ISSN (Electronic): 1750-2659

Publication date (Electronic): 09 March 2012

Publication date (Print): January 2013

Volume: 7

Issue: 1 ( doiID: 10.1111/irv.2012.7.issue-1 )

Pages: 35-45

Affiliations

[ ¹ ]Statistics Unit, Health Protection Agency Centre for Infections, London, UK

[ ² ]Respiratory Diseases Department and Immunisation, Hepatitis and Blood Safety Department, Health Protection Agency Centre for Infections, London, UK.

Author notes

[*]Richard Pebody, Respiratory Diseases Department, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, UK. E‐mail: richard.pebody@ 123456hpa.org.uk