The prevalence of both diabetes and obesity increased with age, and * especially high in ≥65-year-olds.

Should * be was/were?

A professional language checker left my usage of "were" in one instance, but changed it to "was" in another.

The google wildcard searches:

"the prevalence of both * was high"


"the prevalence of both * were high"

both give a couple of examples, but it does not seem conclusive.

  • The sample sentence has a comma problem. You can drop the comma and use and was or retain the comma and add a subject to the second clause. The subject you choose will determine what verb to use. I'd probably refer to rates instead of prevalence if I wanted to regard them separately. That would also clear up the verb choice.
    – Phil Sweet
    May 9 '16 at 22:06
  • 1
    "The prevalence of both diabetes and obesity increased with age, and rates were especially high in ≥65-year-olds." Thanks, this keeps the original structure, but seems more correct
    – CarlAH
    May 10 '16 at 0:04

This is a tricky question, because prevalence is an uncountable noun. Consider what happens with a countable noun. In that case, the verb has to agree with the subject.

The speed of the race car and the motorcycle was too high for me to recognize the drivers.
The speeds of the race car and the motorcycle were too high for me to recognize the drivers.

You could use the singular speed if they were going the same speed, but if they are going two different speeds, you have to use the plural.

For the OP's question, presumably diabetes and obesity each have a different prevalence, so you need the plural:

The prevalence of both diabetes and obesity increased with age, and were especially high in ≥65-year-olds.

To show that you can't always use the singular in cases like this, consider a slightly altered question:

*The prevalence of obesity and malnutrition is anticorrelated.
The prevalence of obesity and malnutrition are anticorrelated.

Here, it's clear you need to use "are".

  • This seems well-argued, so I changed the accepted answer to this one. Sorry if it seems like I am rushing to accept answers. If anyone wants to refute this answer with logic or examples, I will consider changing the accepted answer. I would normally follow votes, but there seems to be no consensus here.
    – CarlAH
    May 10 '16 at 19:28
  • I actually think the best solution is the one in your comment: use rates instead of prevalence for the second part. I have no idea whether any grammatical authorities have considered this question, but this is my intuition as a native English speaker. May 10 '16 at 20:35
  • @Peter Shor BTW, where do you get that prevalence is an uncountable noun? Prevalences is well established in exactly this sense. ngram
    – Phil Sweet
    May 11 '16 at 20:37
  • @Phil: According to the dictionary, prevalance is uncountable. And look at the Ngram comparing the frequencies of prevalence and prevalences. If prevalence were countable, prevalences would be much more common. May 11 '16 at 21:54
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    @PeterShor I see, but like many uncountable nouns, it sometimes has a plural form, and the OP's Q could be written as "The prevalences of both diabetes and obesity increased with age and were especially high in ≥65-year-olds."
    – Phil Sweet
    May 11 '16 at 23:13


To my intense embarassment I have to say that this accepted answer is not correct for the sentence “The prevalence of both...”. The subject is prevalence, singular, and therefore the verb must be the singular, ‘was’. I offer my profound apologies.

Answer to a different question

If the sentence had been “Both diabetes and obesity increased with age...” the verb would be the plural, ‘were’.

The ‘and’ in ‘Both X and Y’ makes it clear that ‘both’ has a plural subject and requires a plural verb in normal usage.

Supporting Sources

I would not have thought it necessary to provide citations to support my statement that ‘both’ requires a plural verb with a plural subject. This seems uncontentious as it is not even treated under the entries for ‘both’ in Gower (‘The Complete plain words’ and ‘English Modern Usage’) or by Fowler and Fowler in ‘The King’s English’). However, as I have been asked for citations, here they are:

“And they were both naked, the man and his wife, and were not ashamed.”

Genesis 2:25 (KJV)

“The Douglas and the Hotspur both together Are confident against the world in arms.”

Shakespeare, Henry IV, Part I [V, 1]

For both were faiths and both have gone.

Mathew Arnold “The Grand Chartreuse”

That said, I must admit that Shakespeare is (as ever) not consistent. Thus:

Nay, come, I pray you, sir, give me the chain:

Both wind and tide stays for this gentleman,

Shakespeare, Comedy of Errors [IV, 1]

But this strikes one immediately as archaic.

  • So the usage of "and" precludes seeing the nouns as non-quantitative?
    – CarlAH
    May 9 '16 at 18:59
  • @CarlAH — I wouldn't know. All I'm saying is when I rephrase it with the 'and' only the plural sounds like English. Like 'Jack and Jill go up the hill'. I couldn't imagine 'goes'.
    – David
    May 9 '16 at 19:09
  • @David Purely opinion based answers aren't good enough. Can you cite a rule or quote a reputable source? Both may very well be plural, but what does that have to do with determining the tense of the verb? It's either not the subject, or not even in the same clause, depending on how the comma problem gets resolved.
    – Phil Sweet
    May 9 '16 at 22:05
  • @PhilSweet — Hadn't realized I'd strayed into a parallel universe where one had to cite the milk that one imbibed at one's mother's breast. But as I'm new here...
    – David
    May 10 '16 at 10:30
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    Aren't we talking about the prevelance, singular, and therefore shouldn't we use "was", ie "The prevalence of both X & Y was high." May 10 '16 at 11:05


The verb agrees with the singular "prevalence", not with "X and Y". So "X and Y were highly prevalent", but "the prevalence ... was high".

  • 1
    So would you say: "The prevalence of obesity and malnutrition is anticorrelated"? May 10 '16 at 12:31

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