David Lloyd Owen - Death and disease defined.
As a guest you can read up to 3 full articles before a subscription is required.
You can read a further 2 articles for free.
John Maynard Keynes crisply summed up our existence by concluding that ‘in the end, we all die.’
The medical profession prefers a more nuanced demise – and acronyms to match. As well as death pure and simple, it employs DALYs (disability- adjusted life years; the burden of disease on humanity) which consist of YLLs (years of life lost) and YLDs (years lived with disability). Just as data regarding access to water and sanitation is of varying quality, numbers for those affected by poor water quality and sanitation provision have tended to be alarmingly variable.
The Global Burden of Disease Study 2010 is a colossal collaboration aimed at getting a firmer grip on who was affected by which diseases in 1990 and 2010, the findings of which were published in The Lancet last month. For water, 119 separate studies were analysed to gain a better understanding of the situation.
What is most striking about the findings is that they indicate that water and sanitation are a lesser factor in disease than had been previously assumed, and that matters appear to be improving. Unimproved water and sanitation accounted for 0.9% of global DALYs in 2010, against 2.1% in 1990. Interestingly, previous Global Burden of Disease studies pointed to their share being 6.8% in 1990 and 3.7% in 2000.
Deaths directly attributed to unimproved water sources fell from 288,007 in 1990 to 116,126 in 2010, and from 496,986 to 244,106 due to unimproved sanitation. For DALYs, the figures fell from 21.17 million to 7.78 million for water, and from 36.05 million to 14.93 million for sanitation. As a result, poor sanitation was the 26th most important risk factor in 2010 (from 15th highest in 1990), with water falling from 22nd to 33rd over the same timeframe.
Looking at causality, the survey concludes that while access to improved water and sanitation had an effect, no clear effect was noted regarding access to piped water or water treatment. The authors did note, however, that this does not take into account the quality of the piped water service or the effectiveness of the treatment used, and so the numbers may be an underestimate.
DALYs due to the broader indicator of diarrhoeal diseases fell from 183.5 million to 89.5 million between 1990 and 2010, the new data suggests. This represents a 51.2% fall, which is even greater when you take into account population growth, as the figure falls by 62.5% from 34.6 per 1,000 people to 13.0 during this time, with diarrhoeal diseases falling from being the second-highest cause of DALYs to the fourthhighest. Regionally, the rates of decline have differed. Most tellingly, diarrhoea fell from 24% of the total 1990 disease burden in South East Asia to 10% by 2010, but from 29% to 16% in South Asia.
If these numbers are right, they have some important implications. Firstly, the oft-quoted figure of three million people a year dying due to unsafe water and sanitation will have to be reconsidered. Secondly, it has to be acknowledged that improving access to safe water and sanitation really works. The danger lies in people deciding that the job is done, and that other priorities matter more now. The timing is doubly important, as the post-2015 targets for water are currently being developed by the United Nations, and it is very much hoped that the next target will be for universal access to safe water and sanitation.
The study also highlights how poor the data continues to be. The 0.4-1.6% confidence range for water and sanitation’s share of the total DALYs burden is especially telling. Poor water and sanitation makes people more susceptible to other diseases, and time spent collecting water constrains economic development, making people more vulnerable to disease.
Meanwhile, the debate continues over what access to ‘improved’ rather than ‘safe’ water and sanitation actually means. If we are to get a meaningful idea about the real impact of water treatment and household piped water on public health, it is hard numbers which will matter when engaging with politicians and policy-makers.