Sleep: Analysis of a 1-Year Diary From 1755–56

Circulating Now welcomes Hartmut Schulz, PhD, and Gerhard Dirlich, PhD, to share their research on an anonymous sleep journal in the collections of the National Library of Medicine. Dr. Schulz is a retired Professor of Psychology (Free University Berlin), and Dr. Gerhard Dirlich is a retired mathematician (Max Planck Intistute of Psychiatry, Munich). Their recent article “Sleep in a 1-year diary from the mid-18th century” can be found in PubMed.

In 1886, the Surgeon General’s Office Library acquired, and registered as number 106347 in its collection, a diary of consumption of solids and fluids, exercise, sleep, amount of urine voided, meteorological observations, etc. for one year, dated Hamburg, August 9, 1755 to August 8, 1756. Nothing is known about the origin of this diary, kept by Anonymous, before it found its way into the Library, to be preserved for future generations. There it remained, perhaps even unopened, while the Surgeon General’s Office Library became the Army Medical Library and finally the National Library of Medicine (NLM), until one of us came across it in the Library’s catalog.

With our interest in sleep history and academic roots in Hamburg, we were immediately intrigued by the keywords sleep and Hamburg associated with this manuscript. We wondered if this diary could perhaps have been a kind of logbook, kept by a ship captain? NLM responded immediately to our e-mail request about the availability of this unique book.  Yes, it was available, and it could be digitized for our research. But as life goes, the COVID-19 pandemic delayed this process for quite a while. However, the wait was worth it, and the digitized copy of the diary eventually arrived, revealing organized daily entries for 366 days (1755 was a leap year), clearly written in English, obviously by a person trained in bookkeeping.

Although scholars have used occasional entries from scattered diary sources to reconstruct sleep behavior in the pre-industrial area, this diary held by NLM is the only one known to us with long-term and precise numerical entries on sleep, which allowed statistical data analysis. With this rare find in hand, the two authors of this post, one a statistician, the other a sleep researcher, resumed a cooperation which had begun 50 years ago.

The special property of the diary entries is the time accuracy of 15 minutes. The diarist used this temporal resolution throughout for entering any sleep-related events and occasionally also for daytime activities. This led us to assume that the diarist used a repeater watch and/or clock. English watchmakers invented repeaters toward the end of the 17th century, and at the time of the diarist they had a precision of 15 minutes. This type of clock had the advantage that the time signal could be called up acoustically without the need for lighting.

“instead of a diary, a nocturnal would more effectually unfold the real dispositions of men”

—William Smellie (1697–1763, Scottish physician and obstetrician)

We have tried to identify the diarist. To do this detective work, we studied all the information in the diary about outdoor activities, places, and persons visited during the year. This data collection revealed that the place of residence at the time was Altona, now a district of Hamburg, or in the surrounding area and that the diarist only moved within a radius of about 20 kilometers. The persons visited were mainly merchants and the pastor of the nearby village Nienstedten. Based on this information we suggest that the anonymous diarist was the English merchant Anthony Simpson, who in 1770 became member of the English Merchant Adventurers, a society with special privileges and of some importance for the city of Hamburg as an international trade center. According to M.S. Wokeck’s Trade in Strangers, Simpson had made a fortune as merchant and ship owner, who had also organized ship transfers of emigrants from Germany to North America. He planned to make Hamburg a new center for emigrants from Northern Germany to save them the long journey to the port of Rotterdam. During these years Simpson built a splendid estate with an extensive English garden. However, these expenses exceeded his financial capabilities, especially since he had bad luck with a further ship transport of emigrants to South Carolina when the expected income did not materialize.

At the same time, his uncle, a London merchant got into trouble and shot himself dead, and on top of these worries his brother, a business partner of his uncle, also died. Anthony Simpson went bankrupt and lost his estate in Nienstedten. He probably spent some time in London to settle family matters after these tragic events.

We also assume that Mr. Simpson may have sought medical advice in this critical life situation, which would be consistent with the entry of a doctor’s address in London (“Maitland. Doctor & Quaker, … London, Lumbard Street, mighty Famous! 1755”) on the inside cover of the diary. The structure of the diary follows closely Hippocrates’ paradigm of sex rebus non naturalibus (six non-natural things: air, rest and activity, sleep and wakefulness, secretions and excretions, states of mind). Attention to these rules was advised to patients from antiquity to the early modern period. Accordingly, the diary contains daily entries about outdoor activities, solid and liquid food, napping, sleep, urination, and weather conditions. If Mr. Simpson had been advised by a doctor to write these things down for a while, this may have prompted him to keep the diary.

When we analyzed the diary, we limited ourselves to the entries on sleep and napping. Due to the high time resolution (quarter hours) it appeared meaningful to convert the entries into numerical data. This transformation enabled us to view the resulting sequences of data as samples of time series and a wide range of mathematical concepts and methods of statistical data analysis became applicable.

We were well aware of the fact that the data depict the sleep-wake structure of just one person in a time interval of one year and should not be generalized to any population. Moreover, we note that only little is known about the environmental conditions in which the observations were collected. Therefore, interpretations suggesting analogies to observations gathered in scientifically correct, controlled conditions should be avoided.

What did the data show?

1. 88% of nights had a duration from 5 to 8 hours. 9% were shorter and 3% were longer.
2. Frequent sleep interruptions, either short interruptions (15 min) or long interruptions (peak at 60 min), corresponding to A.R. Ekirch’s concept of segmented sleep in the pre-industrial time.
3. Comparing rising times during the period of 120 bright days with the period of 120 dark days revealed a distinct effect. A significant shift of the rising times with respect to clock time was found. Rising time was earlier during the bright days period. This indicates alterations of the temporal positioning of sleep with respect to clock time. It indicates possible influences of the cyclic annual variation of the daylight conditions.

The diary data may contribute to a better understanding of sleep in the pre-industrial time, even if they are valid only for a single person, probably a merchant who was no longer in business. At the same time, the anonymous is an early example of what is called today Citizen Science.