The following is taken from a reworked version of an article where some sentences have been reordered. Do you think "therefore" properly connects the sentences?

The “sweet spot” for sleep is when you can sleep continuously through the four stages of sleep four to six times each night. Since each cycle is roughly 90 minutes long, most people need seven to eight hours of relatively uninterrupted sleep to achieve this goal. A chronic lack of sleep, therefore, impacts your ability to pay attention, learn new things, be creative, solve problems and make decisions.

  • Grammatically it's fine (I'd prefer therefore at the beginning of the sentence, but I think it's valid). Semantically, I don't like it - I don't think that sentence follows directly from or forms a logical conclusion to any of the two sentences before it - but that's a matter of opinion and interpretation. Dec 2, 2021 at 13:03

2 Answers 2


This is not a good use of therefore, since there is no clear causal connection between the statements that precede and follow it - the statements are related, but not causally. The first two sentences simply state the amount of time needed to get a good night's sleep. The third sentence describes what happens if you don't get enough sleep, but that isn't causally related to the specific amount of time that makes a good night's sleep.

The paragraph as written could be paraphrased as follows:

A chronic lack of sleep impacts your ability to pay attention because most people need 7-8 hours of uninterrupted sleep.

This sentence isn't logically true, the effects of chronic lack of sleep don't occur because people need 7-8 hours of sleep. They occur because people don't get enough sleep, however much that is - the effects of chronic lack of sleep is not a consequence of the amount of time people need to sleep. Chronic lack of sleep would still have the same effects even if people needed 15-16 hours of sleep per day. It is not a logical consequence of the fact that people go through 4-6 cycles of 90 minutes each.

To think of it another way, if you told an alien that humans need 7-8 hours of sleep, they would have no means of concluding from that statement alone that a chronic lack of sleep has all the effects you listed. Conversely, if you told them the effects of chronic lack of sleep, they would have no means of deducing how much sleep humans need.


"Therefore" has the meaning of "as a consequence". Since your sentence still has meaning with "as a consequence" instead of "therefore", then "therefore" is used OK.

However, it is a bit disruptive to have "therefore" placed as in your example. I would prefer (at least in this case) to have "therefore" placed at the beginning of the sentence - although it is not a mistake to leave it there.

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