“Malaria deaths twice as high as was thought,” The Independent has reported today. Many newspapers have covered research that found that malaria claimed 1.2 million lives worldwide in 2010. The Guardian also reveals that the study “demolishes conventional thinking” that almost all malaria deaths are in babies and small children under the age of five.

Malaria-related deaths in the UK were not examined in this study. Malaria is not generally present in the UK, but this preventable disease is commonly contracted by unprepared travellers visiting tropical and subtropical regions. In recent years, newspapers have reported several cases of high-profile people who have caught malaria, including pop star Cheryl Cole and Premiership footballer, Didier Drogba.

The headlines are based on a disease-modelling study that examined a large database, alongside a systematic review of other studies, to identify deaths due to malaria across 105 countries over the past 30 years. The research found that malaria in 2010 was the cause of death for 1.2 million individuals, including 714,000 deaths in children younger than five years and 524,000 in individuals aged five years or older. The results tend to show an increase in mortality from 1980 to peak levels in 2004, but since then a clear decline.

The researchers say that the recent decrease in malaria mortality in Africa in particular is due to an increase in measures to control the disease, which has been supported by international help. They say that support from international donors needs to increase if malaria is to be eradicated.

However, the primary aim of this study was to predict trends over time in malaria mortality, not to try to find causes for malaria mortality or to examine the effectiveness of different solutions to the problem.

Where did the story come from?

The study was carried out by researchers from the University of Washington, Seattle, and the University of Queensland in Australia, and was funded by The Bill & Melinda Gates Foundation.
It was published in the peer-reviewed medical journal The Lancet. The papers accurately reflected the findings of the research.

What kind of research was this?

This was a modelling study that involved collecting all available data on malaria mortality between 1980 and 2010. During the past 10 years, efforts to tackle malaria have increased. This study aimed to accurately assess the trends in malaria mortality in order to check the progress of these efforts, and to identify areas that need future attention. To do this, the researchers developed a range of models to estimate mortality by age, sex, country and year.

What did the research involve?

As part of the Global Burden of Disease 2010 Study, all available data for mortality by cause from 1980 to 2010 are being systematically collated, and the researchers used this along with the Malaria Atlas Project (MAP). The MAP monitored the levels of transmission of Plasmodium falciparum (the parasite that causes the most severe form of malaria) in different countries.

The researchers describe how they used a large database to identify systematically all data for deaths identified as due to malaria. The researchers restricted their analyses to 105 countries that had information on malaria transmission during the 30-year period of interest. For countries that had eliminated malaria during this period, they identified the year of elimination and estimated the number of malaria deaths for the period when transmission was still occurring.

The researchers supplemented the information identified with a search of the global literature to identify published and unpublished ‘verbal autopsy’ studies. These record the probable cause of death based on the deceased’s symptoms and likely medical diagnosis. The verbal autopsy method tends to be used in countries that lack a formal and reliable system for registering deaths. These were population-based studies that covered a period of at least one year and provided the number of deaths by cause according to verbal autopsy. The verbal autopsy method tends to be used in countries that lack a formal and reliable system for registering deaths.

In order to develop their models they divided the world into three groups:

• countries from sub-Saharan Africa and Yemen (45 countries)
• countries outside of sub-Saharan Africa (45 countries)
• countries with only Plasmodium vivax malaria (15 countries)

Malaria deaths in countries that only have Plasmodium vivax malaria are lower than others, so for these countries the researchers simply modelled malaria death rate by age. For the other 90 countries the researchers tested different predictive models, including:

• looking separately by sex
• looking separately by age group (less than five years and five years and older)
• looking at the transmission intensity of Plasmodium falciparum malaria, which is a key predictor of the number of malaria deaths

What were the basic results?

The study provides extensive mortality data by country. Overall, the researchers observe a fluctuation in the number of malaria deaths worldwide over the 30-year period:

• 995,000 deaths in 1980 (95% confidence interval CI 711,000 to 1,412,000)
• a peak level of 1,817,000 deaths in 2004 (95% CI 1,430,000 to 2,366,000)
• a decrease to 1,238,000 deaths in 2010 (95% CI 929,000 to 1,685,000)

In Africa there were:

• 493,000 deaths in 1980 (95% CI 290,000 to 747,000)
• an increase to 1,613,000 in 2004 (95% CI 1,243 000 to 2,145,000)
• about a 30% decrease to 1,133,000 in 2010 (95% CI 848,000 to 1,591,000)

Outside of Africa, malaria deaths have steadily decreased:

• 502,000 in 1980 (95% CI 322,000 to 833,000)
• down to 104,000 in 2010 (95% CI 45,000 to 191,000)

The researchers estimated that there have been more deaths in people aged five years or older than previous studies have estimated. In 2010 there were 435,000 deaths in over-fives in Africa (95% CI 307,000 to 658,000) and 89,000 deaths in over-fives outside of Africa (33,000–177,000). The comparative 2010 figures for under-fives are 699,000 deaths (95% CI 415,000 to 1,112,000) in Africa and 15,000 deaths (95% CI 4,300 to 31,000) outside of Africa.

Deaths in both under- and over-fives have been decreasing over the past five years. However, the trend of deaths for countries within Africa is different to that for those of countries outside of Africa: in Africa deaths have declined in both the under- and over-fives in the past five years, though deaths in the under-fives still remain clearly higher than those in the over-fives; outside of Africa deaths in both age groups have also steadily declined, though here the mortality rate in the over-fives is higher than those below this age.

How did the researchers interpret the results?

The researchers conclude that their findings show that the global malaria mortality burden is larger than previously estimated, especially in adults. They say that the recent decrease in malaria mortality in Africa is due to more measures being taken to control the disease, which has been supported by international help. However, they say that support from international donors needs to increase if malaria is to be eradicated.

Conclusion

This study has looked at a lot of data and used systematic methods to examine trends in malaria mortality over the past 30 years. It shows that malaria in 2010 was the cause of death for 1.2 million individuals, including 714,000 deaths in children younger than five years and 524,000 in individuals aged five years or older. The results tend to show an increase in mortality from 1980 to peak levels in 2004, but since then a clear decline.

The researchers say that the recent decrease in malaria mortality in Africa in particular is due to malaria control activities being increased, supported by international help. They say that support from international donors needs to increase further if malaria is to be eradicated.

However, the primary aim of this study was to predict trends over time in malaria mortality, not to try to find causes for malaria mortality or to examine the effectiveness of different solutions to the problem.

Links To The Headlines

Malaria is twice as deadly as first thought after disease claims 1.2million lives in a year. Daily Mail, February 2 2012

Malaria death toll far higher than previously thought. The Daily Telegraph, February 2 2012

Malaria kills 1.2m worldwide – double the level feared. Metro, February 2 2012

Malaria kills twice as many people as previously thought, research finds. The Guardian, February 2 2012

Malaria deaths twice as high as was thought. The Independent, February 2 2012

Links To Science

Murray CJL, Rosenfeld LC, Lim SS, et al. Global malaria mortality between 1980 and 2010: a systematic analysis. Lancet 2012; 379: 413–31

Editorial: New estimates of malaria deaths: concern and opportunity. The Lancet, 2012:379;385

A new study has found that “patients are more likely to die in hospital if they are admitted at the weekend,” according to BBC News. The broadcaster said the research backs up previous studies suggesting patients admitted at the weekend have a lower chance of survival.

The new study in question looked at over 14 million admissions to English NHS hospitals over the financial year of 2009/10. Researchers looked at risk of patients dying from any cause within 30 days of admission, taking into account various other factors that could influence the risk, such as age, reason for admission, and other medical illnesses. During the year there were 187,337 deaths that occurred within 30 days of admission, equating to 1.3% of all those hospitalised. When they looked at factors associated with risk they found a person admitted on a Sunday had 16% increased risk of dying following admission compared to a person admitted on a Wednesday. Conversely, patients were more likely to die mid-week day rather than a Saturday or Sunday.

While the study has found a pattern relating to admission day and the risk of dying, the reasons for this are unknown and it should not be assumed that the pattern is due to staffing levels or the availability of senior staff. There could be various reasons for the relationship; for example, it may be that people who need to see the doctor and be admitted on a weekend have more severe illness than people who would wait until the following Monday to be admitted. While this very large study has found a pattern, it will take further delving to unlock the reasons why, which are likely to be more complex than simply the availability of staff.

Where did the story come from?

This study was authored by researchers from University College London and various other institutions in the UK. The study was published in the Journal of the Royal Society of Medicine and received no outside funding.

What kind of research was this?

This was a retrospective cohort study aiming to see if being admitted at the weekend carried a higher risk of mortality than admission on a weekday. To do so the researchers looked at all hospital admissions that occurred within the NHS over the 2009/10 financial year. It was concerned with ‘30-day mortality’, that is, deaths occurring within 30 days of a hospital admission (either in or out of hospital).

The researchers adjusted their analysis to account for various factors that could have affected this risk, but do not describe how the severity of patients’ conditions was taken into account. This means it is difficult to tell how effectively this potentially major confounder has been accounted for. The severity of a patient’s illness, the type of care provided to them and the differences in their outcome are likely to relate to each other in complex ways, and so the topic will need further careful analysis.

What did the research involve?

The researchers analysed all admissions to the English National Health Service (NHS) during the
financial year 2009/10. They linked admission records to official mortality data from the Office of National Statistics to identify all deaths that occurred within the 30 days following an admission (both those occurring in or out of hospital).

Using their data the researchers then developed statistical models to account for risk of death following admission. In their main model they adjusted for factors that were likely to have a strong effect on mortality risk:

• age
• sex
• ethnicity
• whether or not the admission was an emergency
• source of admission (for example, from home or transfer from another hospital)
• diagnosis; number of previous emergency admissions
• number of previous ‘complex’ admissions
• medical co-morbidities
• social deprivation
• hospital trust
• day of the year (seasonality)
• day of the week admission occurred on

They looked at both risk associated with being admitted over the weekend, and with staying in hospital over the weekend (admitted during the week but being an inpatient over the weekend).

What were the basic results?

There were 15,061,472 admissions to the NHS in England over this one-year period, and the researchers had information on 30-day mortality and other patient characteristics for 14,217,640 of them (95% of all admissions). There were 187,337 deaths in hospital within 30 days of admission. Admission on weekend days was associated with an increased risk of 30-day death compared with admission on weekdays:

• Sunday admissions were associated with a 16% increased risk compared to those on a Wednesday (hazard ratio [HR] 1.16, 95% confidence interval [CI] 1.14 to 1.18)
• Saturday admissions were associated with an 11% greater risk versus Wednesday admissions (HR 1.11, 95% CI 1.09 to 1.13).

Conversely, deaths were more likely to occur during the week than at the weekend. Staying in hospital on a Sunday was associated with a slightly lower risk of death than staying in hospital on a Wednesday (HR 0.92, 95% CI 0.91 to 0.94), as was staying in hospital on a Saturday (HR 0.95, 95% CI 0.93 to 0.96).

There were 284,852 deaths overall – both in an out of hospital – and 34% of people that died did so after they had been discharged from hospital. Results for the researchers’ subsequent model, examining all deaths, not just those occurring in a hospital, were similar.

How did the researchers interpret the results?

The researchers conclude that admission to hospital at the weekend is associated with increased risk of dying within 30 days of admission. However, death is more likely to occur on a mid-week day than a weekend.

Conclusion

The main finding of this study was that being admitted to hospital at the weekend (Saturday or Sunday) is associated with a significant increased risk of death over the following 30-days. This study has strengths in that it has used an extremely large and reliable data set representative of almost all hospital admissions within the NHS in England during one financial year. The researchers’ model also accounted for a wide range of medical and sociodemographic factors and characteristics of admission that could have influenced the risk of death.

While the researchers’ models adjusted for a variety of important confounders, it is difficult to see from the report how they did this, making it difficult to decide whether all relevant factors have been appropriately adjusted for. Most importantly, this study has not examined the reasons why there may be increased risk of death with weekend admission, so no assumptions should be drawn about staffing levels or the availability of senior staff.

It is important to be aware that an increased risk of subsequent death of 16% (Sunday compared to Wednesday) is a relative measure, representing an increase of only about two extra deaths for every 1,000 people admitted on a weekend compared to a weekday (a x 0.16 relative increase beyond a 13 per 1,000 average baseline risk of death).

The researchers do offer some potential reasons for the patterns seen, putting forward the hypothesis that patients admitted at the weekend may include patients whose illness may have been severe enough to justify not waiting until a week day, while those who were less ill may have waited rather than going to the hospital at the weekend. This is an interesting, and indeed plausible theory, but it is not clear how the researchers adjusted severity of illness in their analysis, and therefore it is not possible to confirm if this phenomenon accounts for the small absolute difference in deaths seen.

Links To The Headlines

You ARE more likely to die if taken to hospital at weekend: Study confirms that NHS care is worse on a Saturday and Sunday. Daily Mail, February 2 2012

Hospital patients more at risk at weekends. The Guardian, February 2 2012

Risk of dying ‘significantly’ higher if you go into hospital on Sunday. Metro, February 2 2012

Links To Science

Freemantle N, Richardson M, Wood J, et al. Weekend hospitalization and additional risk of death: An analysis of inpatient data. Journal of the Royal Society of Medicine. Published online on February 2 2012