As I had a teacher at school who was always really picky on how to draw conclusions I must say that the conclusions you drew for your health situation might be true, but dangerous. For example: If slightly more women than men suffer from health deseases it could be wise to write the information toward women. But, if you take search behaviour into account thing could look a lot different: It might turn up that men search more than women or that (senior) men are more present on the net than women.
You can confer some of your site's reputation to another site when your site links to it. Sometimes users can take advantage of this by adding links to their own site in your comment sections or message boards. Or sometimes you might mention a site in a negative way and don't want to confer any of your reputation upon it. For example, imagine that you're writing a blog post on the topic of comment spamming and you want to call out a site that recently comment spammed your blog. You want to warn others of the site, so you include the link to it in your content; however, you certainly don't want to give the site some of your reputation from your link. This would be a good time to use nofollow.
Social media. The algorithms have truly changed since social media first emerged. Many content websites are community-oriented -- Digg began allowing users to vote which stories make the front page, and YouTube factors views and user ratings into their front page rankings. Therefore, e-commerce stores must establish a strong social media presence on sites like Facebook , Pinterest, Twitter, etc. These social media sites send search engines signals of influence and authority.
Another way to increase traffic to your website is to get listed in free online directories and review sites. For most of these sites, your profile will have a link to your website, so actively updating these listings and getting positive reviews is likely to result in more website traffic. In addition, many directories like Yelp have strong domain authority on Google. There’s a chance that your business’s free Yelp page could rank high for relevant searches.