Closing unused accounts not only lowers the amount of revolving accounts, which is an indication of creditworthiness, but it also decreases your total amount of available credit. (blog.compmort.com)
Your debt to credit ratio may also be affected by closing unused accounts as the amount of their limit comes of the top of your overall credit. (rewardexpert.com)
In general, yes, keeping those old unused accounts open will improve your score. (freemoneyfinance.com)