The medical origins of washing hands dates back to Dr. Semmelweis in mid 19th century. He managed to bring down the mortality rate of mothers giving birth, by emphasizing the importance of washing hands. Let’s analyze the data that made Semmelweis realize that something was wrong with the procedures at Vienna General Hospital.
Meet Dr. Ignaz Semmelweis
This is Dr. Ignaz Semmelweis, a Hungarian physician born in 1818 and active at the Vienna General Hospital. If Dr. Semmelweis looks troubled it's probably because he was thinking about childbed fever: A deadly disease affecting women that just have given birth. He was thinking about it because in the early 1840s at the Vienna General Hospital as many as 10% of the women giving birth die from it. He was thinking about it because he knows the cause of childbed fever: It's the contaminated hands of the doctors delivering the babies. And they won't listen to him and wash their hands!
Yearly births and deaths across 2 clinics:
year births deaths clinic 0 1841 3036 237 clinic 1 1 1842 3287 518 clinic 1 2 1843 3060 274 clinic 1 3 1844 3157 260 clinic 1 4 1845 3492 241 clinic 1 5 1846 4010 459 clinic 1 6 1841 2442 86 clinic 2 7 1842 2659 202 clinic 2 8 1843 2739 164 clinic 2 9 1844 2956 68 clinic 2 10 1845 3241 66 clinic 2 11 1846 3754 105 clinic 2
The alarming number of deaths
The table above shows the number of women giving birth at the two clinics at the Vienna General Hospital for the years 1841 to 1846. Giving birth was very dangerous; an alarming number of women died as the result of childbirth, most of them from childbed fever.
We see this more clearly if we look at the proportion of deaths out of the number of women giving birth. Let's zoom in on the proportion of deaths at Clinic 1.
year births deaths clinic proportion_deaths 0 1841 3036 237 clinic 1 0.078063 1 1842 3287 518 clinic 1 0.157591 2 1843 3060 274 clinic 1 0.089542 3 1844 3157 260 clinic 1 0.082357 4 1845 3492 241 clinic 1 0.069015 5 1846 4010 459 clinic 1 0.114464
Death at the clinics
If we now plot the proportion of deaths at both clinic 1 and clinic 2 we'll see a curious pattern…
Text(0, 0.5, 'Proportion deaths')
The handwashing begins
Why is the proportion of deaths constantly so much higher in Clinic 1? Semmelweis saw the same pattern and was puzzled and distressed. The only difference between the clinics was that many medical students served at Clinic 1, while mostly midwife students served at Clinic 2. While the midwives only tended to the women giving birth, the medical students also spent time in the autopsy rooms examining corpses.
Semmelweis started to suspect that something on the corpses, spread from the hands of the medical students, caused childbed fever. So in a desperate attempt to stop the high mortality rates, he decreed: Wash your hands! This was an unorthodox and controversial request, nobody in Vienna knew about bacteria at this point in time.
Let's load in monthly data from Clinic 1 to see if the handwashing had any effect.
date births deaths proportion_deaths 0 1841-01-01 254 37 0.145669 1 1841-02-01 239 18 0.075314 2 1841-03-01 277 12 0.043321 3 1841-04-01 255 4 0.015686 4 1841-05-01 255 2 0.007843
The effect of handwashing
With the data loaded we can now look at the proportion of deaths over time.
Text(0, 0.5, 'Proportion Deaths')
Starting from the summer of 1847 the proportion of deaths is drastically reduced and, yes, this was when Semmelweis made handwashing obligatory.
Text(0, 0.5, 'Proportion Deaths')
More handwashing, fewer deaths?
Again, the graph shows that handwashing had a huge effect. How much did it reduce the monthly proportion of deaths on average?
Change in Proportion of Deaths After Washing minus Before Washing: -8.40%
A Bootstrap analysis of Semmelweis handwashing data
It reduced the proportion of deaths by around 8 percentage points! From 10% on average to just 2% (which is still a high number by modern standards).
To get a feeling for the uncertainty around how much handwashing reduces mortalities we could look at a confidence interval (here calculated using the bootstrap method).
95% Confidence Interval: 0.025 -0.100916 0.975 -0.066943
The fate of Dr. Semmelweis and his theory
So handwashing reduced the proportion of deaths by between 6.7 and 10 percentage points, according to a 95% confidence interval. All in all, it would seem that Semmelweis had solid evidence that handwashing was a simple but highly effective procedure that could save many lives.
The tragedy is that, despite the evidence, Semmelweis' theory — that childbed fever was caused by some "substance" (what we today know as bacteria) from autopsy room corpses — was ridiculed by contemporary scientists. The medical community largely rejected his discovery and in 1849 he was forced to leave the Vienna General Hospital for good.
Statistics and statistical arguments were uncommon in medical science in the 1800s. His practice earned widespread acceptance only years after his death.
Dr. Semmelweis is described even today as "the saviour of mothers".
For more detail, code and interactive graphs Visit Notebook
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