Hello Arun
It is hard to put it all in an answer. But you might benefit from the following links:
http://www.csun.edu/~scaesar/school/sed600/HowUniversalisGoodDesignforOlderUsers.pdf[
^] : Talks about how little work on application design exists for older users and tips on the subject. This is probably the best solution for you.
http://www.diva-portal.org/smash/get/diva2:416488/FULLTEXT01.pdf[
^]: Similar to the above, but the article is way bigger. It might be quite helpful, but I don't know how much depth you need. Have a look at page 8 on Cognitive Decline and and page 20 starting on user friendly technologies.
http://www.guide-project.eu/includes/requestFile.php?id=118&pub=2[
^]: a handbook of recommended practices and design principles aimed at usability for elderly.
Well, that is what I have. Luckly for you I had something similar at university not so long ago... This should get you started, for more you will probably have to google/yahoo/bing it, a lot...
Regards