I saw 65 years old or older used by reliable sources such as the New York Times. Does "old" and "older" sound repetitive, or is it just the way to say it? Would it be better to use "65 years old or higher" or "65 years old or greater"?
Also, for this graph, should I use "65 years old or older" or "65 years old and older"?
1n 1940 approximately 7% of Sweden’s population was 65 years old or/and older/higher/greater.
The most idiomatic choices of preposition are:
'Greater' and 'higher' are simply just not idiomatic when speaking about age, although you can use 'higher' when referring back to the group (eg "the higher age groups"), it just isn't natural to call the group by that.
Which you use from among the idiomatic choices is up to you, unless you are working with a style guide.
As to the question of 'or/and' - this depends on whether you are presenting an option or not. For example:
In example 1, an individual ('you') is referred to. They can only be one age, so they must be 18 or over. Example 2 refers, not to an individual, but to anyone that can enter the bar - those aged 18 and those aged over 18. Your specific example is referring to a group, so use 'and'.
