Yes. Screen readers load the page contents into a buffer and allow users to scan headings, links, etc. having a broken outline structure is potentially confusing [1]. This is also why descriptive linked text is important (ie: no "click here") [2]

[1]: http://www.w3.org/TR/WCAG20-TECHS/H42.html [2]: http://www.w3.org/TR/WCAG20-TECHS/H30.html