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Efeitos de uma onda de calor na mortalidade
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RESUMO - Existem vários estudos que revelam uma associação entre
o aumento da mortalidade e do calor, medida quer pela
temperatura máxima ou mínima, por índices de calor e,
por vezes, por outras condições meteorológicas. Efeitos na
saúde parecem estar associados à exposição do corpo
humano a temperaturas elevadas e prolongadas acima das
quais a população está habituada (Mcgeehin e Mirabelli,
2001).
Foram usados dados de mortalidade (INE) nos períodos de
Verão de 1990, 1991 e 1992 e dados das temperaturas diárias
do ar em Julho de 1991, com o objectivo de estimar o
exacto período da onda de calor em Portugal e o respectivo
excesso de óbitos verificados, bem como estudar a sua distribuição
por sexo, grupo etário, distrito de residência e as
diferentes causas de morte.
Consideraram-se expostos a ondas de calor os distritos
onde se registam temperaturas máximas iguais ou superiores
a 32,0ºC durante um intervalo de dois ou mais dias
consecutivos.
Estimou-se o excesso de óbitos total por dia e o excesso de
óbitos por sexo, grupo etário, distrito de residência, causa
de morte pela diferença entre o número de óbitos observado
e o número de óbitos esperado. O número de óbitos
esperado em cada dia foi obtido através da determinação
do número médio de óbitos ocorrido entre 1 de Maio e
31 de Agosto de 1990, 1991 e 1992, excluindo os dias afectados
pela onda de calor. Avaliou-se o significado de o
excesso de óbitos pelo estudo da significância estatística
da razão óbitos observados/óbitos esperados (O/E) sob
hipótese nula O/E ser igual a 1, vs. hipótese alternativa
O/E ser superior a 1, tendo-se assumido que a ocorrência
dos óbitos seguia uma distribuição de Poisson. No
entanto, sempre que o número de óbitos observado foi
superior a 100, utilizou-se a respectiva aproximação à
distribuição normal.
Entre 8 e 22 de Julho de 1991, todos os distritos de Portugal
continental estiveram expostos a uma onda de calor. No
mesmo ano, de 12 a 21 de Julho, verificou-se um número
de óbitos diário significativamente superior ao esperado,
tendo-se estimado a nível nacional e para esse período um
excesso de 1002 óbitos. Verificou-se um excesso de óbitos
em ambos os sexos e em todos os grupos etários, com
excepção das crianças, em ambos os sexos, dos 0 aos 4 anos
de idade e das mulheres dos 25 aos 54 anos.
A análise por distrito revelou um excesso de mortalidade
em todos os distritos expostos, com excepção de Aveiro,
Viana do Castelo e das Regiões Autónomas dos Açores e da
Madeira.
De entre as causas de morte associadas à onda de calor
destacam-se as doenças do aparelho circulatório, responsáveis
por um excesso estimado de 472,3 óbitos, sendo as doenças cérebro-vasculares responsáveis por cerca de 29%
do total de excesso de óbitos. As neoplasias malignas apresentaram
um excesso de cerca de 139 óbitos. No grupo
nosológico das doenças do aparelho respiratório (com 112
óbitos em excesso) destaca-se a causa por broncopneumonia
e pneumonia por microorganismos não especificados.
O grupo dos sintomas, sinais e afecções mal definidas foi
também um dos mais afectados, com aproximadamente
105 óbitos em excesso.
Da análise da razão O/E destacaram-se ainda as seguintes
causas:
— Efeitos do calor e da luz (razão O/E = 89,7);
— Doenças da pele e do tecido subcutâneo (razão O/E = 7,0);
— Doenças do sistema osteomuscular e do tecido conjuntivo
(razão O/E = 4,5);
— Queimaduras (razão O/E = 4,7);
— Afogamento (razão O/E = 3,1);
— Doenças do sangue e dos órgãos hematopoéticos (razão
O/E = 2,7);
— Doença hipertensiva (razão O/E = 2,2);
— Sintomas (razão O/E = 2,2);
— Broncopneumonia e pneumonia por microorganismos
não especificados (razão O/E = 2,2).
ABSTRACT - Studies in urban areas show an association between increases in mortality and increases in heat, measured by maximum or minimum temperature, heat index, and sometimes, other weather conditions. Health effects associated with exposure to extreme and prolonged heat appear to be related to environmental temperatures above those the population is used to have. Physiologic and behavioural adaptations may reduce morbidity and mortality. Within heat-sensitive regions, urban populations are the most vulnerable to adverse heat-related health outcomes. The elderly, young children, the poor and people who are bedridden or are on certain medications are at particular risk (Mcgeehin and Mirabelli, 2001). In this study the objective was the estimative of exact date of July 1991 heat wave and excess of deaths estimative. We used mortality data (supplied by Instituto Nacional de Estatística) relatively to the Summer’s of 1990, 1991 and 1992 and daily maximum temperature of July 1991 (supplied by Instituto de Meteorologia). All inhabitants of the districts where daily maximum temperatures were equal or higher than 32.0ºC for 2 or more consecutive days were considered as the exposed population. Excess of deaths was estimated by day, age, gender, district of residence and by each relevant causes of death. Excess of deaths was derived as the difference of observed number of deaths (O) and the expected number of deaths (E). The expected number of daily deaths was derived through the mean number of deaths observed from 1st May to 31st August from the years 1990, 1991 and 1992, excluding the days of the heat wave (July 12 to July 21, 1991). To test the statistical significance of O/E ratios (under the null hypothesis O/E = 1 vs alternative hypothesis O/E > 1) it was assumed that the occurrence of deaths follows a Poisson distribution, with a mean equal to the expected number of deaths per day. The exact Poisson probabilities have been derived when the expected number of deaths was below 100, otherwise a normal distribution approximation has been used. From July 8 through July 22 of 1991, the Portuguese continent was exposed to a heat wave. An estimative of approximately 1002 excess deaths has been obtained for the period from July 12 to July 21, 1991. The excessive number of deaths was found in males and females, and in all age group, except in children of both sexes from 0 to 4 years old and in females from 25 to 54 years old. We found an excess of mortality in all districts, except in Aveiro, Viana do Castelo and in the islands Açores e Madeira. The more relevant causes of death in the period affected by the heat wave were the diseases of the circulatory system, with an estimated excess of 472.3 deaths. Cerebrovascular diseases are responsible for 29% of the total of the excess of mortality. Malignant neoplasm had an estimated excess near of 139 deaths. In the group diseases of the respiratory system (with 112 excess deaths) the more relevant cause was bronchopneumonia and pneumonia by organisms unspecified. One of the most affected was also the group symptoms, signs and ill-defined conditions, with approximately 105 excess deaths. Analysing O/E ratios, we can see that the most relevant causes were: — Heat-related illness (O/E ratio = 89.7); — Diseases of the skin and subcutaneous tissue (O/E ratio = 7.0); — Diseases of the musculoskeletal system connective (O/E ratio = 4.5); — Burn (O/E ratio = 4.7); — Drawing (O/E ratio = 3.1); — Diseases of the blood and blood – forming organs (O/E ratio = 2.7); — Hypertensive Disease (O/E ratio = 2.2); — Symptoms (O/E ratio = 2.2); — Bronchopneumonia and pneumonia by organisms unspecified (O/E ratio = 2.2).
ABSTRACT - Studies in urban areas show an association between increases in mortality and increases in heat, measured by maximum or minimum temperature, heat index, and sometimes, other weather conditions. Health effects associated with exposure to extreme and prolonged heat appear to be related to environmental temperatures above those the population is used to have. Physiologic and behavioural adaptations may reduce morbidity and mortality. Within heat-sensitive regions, urban populations are the most vulnerable to adverse heat-related health outcomes. The elderly, young children, the poor and people who are bedridden or are on certain medications are at particular risk (Mcgeehin and Mirabelli, 2001). In this study the objective was the estimative of exact date of July 1991 heat wave and excess of deaths estimative. We used mortality data (supplied by Instituto Nacional de Estatística) relatively to the Summer’s of 1990, 1991 and 1992 and daily maximum temperature of July 1991 (supplied by Instituto de Meteorologia). All inhabitants of the districts where daily maximum temperatures were equal or higher than 32.0ºC for 2 or more consecutive days were considered as the exposed population. Excess of deaths was estimated by day, age, gender, district of residence and by each relevant causes of death. Excess of deaths was derived as the difference of observed number of deaths (O) and the expected number of deaths (E). The expected number of daily deaths was derived through the mean number of deaths observed from 1st May to 31st August from the years 1990, 1991 and 1992, excluding the days of the heat wave (July 12 to July 21, 1991). To test the statistical significance of O/E ratios (under the null hypothesis O/E = 1 vs alternative hypothesis O/E > 1) it was assumed that the occurrence of deaths follows a Poisson distribution, with a mean equal to the expected number of deaths per day. The exact Poisson probabilities have been derived when the expected number of deaths was below 100, otherwise a normal distribution approximation has been used. From July 8 through July 22 of 1991, the Portuguese continent was exposed to a heat wave. An estimative of approximately 1002 excess deaths has been obtained for the period from July 12 to July 21, 1991. The excessive number of deaths was found in males and females, and in all age group, except in children of both sexes from 0 to 4 years old and in females from 25 to 54 years old. We found an excess of mortality in all districts, except in Aveiro, Viana do Castelo and in the islands Açores e Madeira. The more relevant causes of death in the period affected by the heat wave were the diseases of the circulatory system, with an estimated excess of 472.3 deaths. Cerebrovascular diseases are responsible for 29% of the total of the excess of mortality. Malignant neoplasm had an estimated excess near of 139 deaths. In the group diseases of the respiratory system (with 112 excess deaths) the more relevant cause was bronchopneumonia and pneumonia by organisms unspecified. One of the most affected was also the group symptoms, signs and ill-defined conditions, with approximately 105 excess deaths. Analysing O/E ratios, we can see that the most relevant causes were: — Heat-related illness (O/E ratio = 89.7); — Diseases of the skin and subcutaneous tissue (O/E ratio = 7.0); — Diseases of the musculoskeletal system connective (O/E ratio = 4.5); — Burn (O/E ratio = 4.7); — Drawing (O/E ratio = 3.1); — Diseases of the blood and blood – forming organs (O/E ratio = 2.7); — Hypertensive Disease (O/E ratio = 2.2); — Symptoms (O/E ratio = 2.2); — Bronchopneumonia and pneumonia by organisms unspecified (O/E ratio = 2.2).
Descrição
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Contexto Educativo
Citação
Paixão, Eleanora de Jesus; Nogueira, Paulo Jorge - Efeitos de uma onda de calor na mortalidade = Heat waves and their effects on mortality. Revista Portuguesa de Saúde Pública. ISSN 0870-9025. Vol. 21, Nº 1 (Janeiro/Junho 2003), p. 41-54
Editora
Universidade Nova de Lisboa, Escola Nacional de Saúde Pública