if category description = empty …

<?php
foreach (get_the_category() as $cat) {
	$parent = get_category($cat->category_parent);
	$parent_name = $parent->cat_name;
	$parent_description = $parent->description;
	echo '<div id="content_headline"><h1>'.$parent_name.'</h1></div>';
	if (strlen($parent_description)>0) {
		echo '<div id="content_main">'.$parent_description.'</div>';
	}
}
?>

I use this code to display the parent cat and it’s description.
The bit to check if there actually is a description does no work … I get the DIVs no matter what.
Any ideas?