Javascript object becomes undefined

I'm programming a simple Twitterbot with JavaScript, but I've hit a problem. For some reason some of my objects become undefined after getting results from Twitter, but some don't. I am using nodeJS and Twit. What could be behind this and how could I solve it?

var hashTags = {};
var dailyStats = {};
//prints out {}
console.log(dailyStats);

setInterval(function() {
    //Prints out {}
    console.log(dailyStats);
    //Prints out {}
    console.log(hashTags);
    var params;
    if(sinceLastTweet === 0){
        params = {
            count: 200
        };
    }
    else{
        params = {
            since_id: sinceLastTweet,
        };
    }

    bot.twit.get('statuses/home_timeline', params, function (err, reply) {
        //Prints out undefined
        console.log(dailyStats);
        //Prints out {}
        console.log(hashTags);
   ...