Memory leak from node/mongoose

Question

The below code dumps all the followers from TWITTER_USERNAME in a mongodb collection. When it's running, the memory utilization of my MongoDB database slowly increases until it crashes. I have to pause the script and restart mongo every few hours to avoid this. Is there a way for the script to get Mongo to release this memory?

var TwitterUserId = require(PATH + "/models/twitterUserId").Model;
var TwitterConnection = require(PATH + "/models/twitterConnection").Model;

util.promiseWhile = Promise.method(function(condition, action, lastValue) {
  if (!condition()) return lastValue;
  return action().then(promiseWhile.bind(null, condition, action));
});

var go = function(cursor) {
  if(!cursor) cursor = -1;

  var pollTwitter = function(cnn) {
    return new Promise(function(resolve,reject) {
      var parms = {
        screen_name: TWITTER_USERNAME,
        stringify_ids:true
        cursor: cursor
      };
      cnn.get('followers/ids', parms,function(err,res) {
        if(err) return reject(err);
        cursor = res.next_cursor_str;
        resolve(res.ids);
      });
    });
  };

  mongoose.connect(config.db.uri,config.db.options)
  .then(function() {
    return TwitterConnection.findOne({});
  })
  .then(function(twitterCnnCOnfig) {
    return new twitterObject({
         consumer_key: twitterCnnCOnfig.consumerKey
        ,consumer_secret: twitterCnnCOnfig.consumerSecret
        ,access_token_key: twitterCnnCOnfig.accessTokenKey
        ,access_token_secret: twitterCnnCOnfig.accessTokenSecret
    });                        
  })
  .then(function(twitterCnn) {
    util.promiseWhile(
      function() {
        return cursor;
      },
      function () {
        return new Promise(function(outerResolve,outerReject) {
          twitter.parms.cursor = cursor;
          pollTwitter(twitterCnn)
          .each(function(twitterId) {
            return new Promise(function(resolve,reject) {
              return TwitterUserId.create({twitterId: twitterId})
              .then(resolve,reject);
            });
          })
          .then(function() {
            setTimeout(function() {
              outerResolve();
            },50 * 1000);
          })
        });
      }
    );
  })
};