Question: Are farts stinkier at night?
Short answer: Yes.
Long answer: Farts are a way of releasing gas that builds up in our intestines throughout the day and night. People often notice that they have more farts or louder farts early in the morning, which would suggest that gas builds up while they sleep. But as we saw in another post, there is only a weak relationship between loudness and smelliness. This makes sense, given the fact that farts are mostly air.
So how does the stinkiness of farts vary across the day? We looked at this in our database of 1619 farts. In order to isolate an effect of time, we normalized the data, by expressing each data point relative to each subject’s mean and standard deviation. The results, shown below, confirm that early-morning farts are not particularly smelly. Indeed, between the hours of 6 and 8 am, farts are typically less smelly than average. There is a gradual tendency for smelliness to increase throughout the day, peaking around midnight in our data. Unfortunately, we have not collected any data between midnight and 6 am, which precludes any conclusion about late-night farts.
Also apparent in the data is a cycle of stinkiness that has a period of about 8 hours. There are peaks at 8 am, 4 pm, and midnight, suggesting a possible synchronization with mealtimes, which would certainly not be surprising.