I used to be a licensed rep for one of the largest Health & Life insurers out there and there are many many issues that can cause a person's rates to go up....or even get dropped.
Getting older (usually in 10 year increments), having expensive health problems or procedures, are obvious reasons. Now that companies cannot discriminate for pre-existing conditions THAT is one expensive problem for companies. Considering if someone had cancer, heart disease, diabetes, stroke, etc. those issues can ring up a very expensive tab in a year when before those people normally couldn't get coverage -- even at a extremely high rate.
Also, it does matter if you get health insurance as an individual or as part of a group (through an employer, i.e.). Individual rates are almost always higher than group. Group rates can go up depending on the health and ages of those in the group. Working at a large law firm, for example, where most all of the employees are over 50 will have far higher rates than a daycare where most of the employees are in their 20's and 30's.
I am not going to get into the problems of the current national problem of health care other than the fact that if you force a business to do something that drastically screws with their bottom line and profit margins they will jack the rates up to compensate themselves for the extra pay-out costs or simply drop a policy holder who seems to be a greater liability to them in a heartbeat -- with usually no recourse available to the "dropee".
Health and life are both things that if you get it while you are young, say early 20's, will always be cheaper...however most young people think they are bulletproof and don't care to get either.