As you might notice all ex-USSR countries, excluding Baltics, which were always more European, share similar life expectancy. I would guess it's because of three factors: tobacco, alcohol and poor social security.
For example:
at least 5 years ago you could smoke in any restaurant and in most public places in Russia. 40% of Russian populations are active smokers. 60% of all males are smoking. 23% of all male population died because of smoking related issue. 40% of males in age 30-59 died because of smoking.
Russia also has issues with minors consuming alcohol, age restriction exists but at least 5 years ago it was not forced, meaning that you could go to a restaurant or even grocery shop and buy alcohol even if you are 14-16, because nobody asks you for an ID. Giving alcohol to minors is also not forcefully restricted, meaning that somebody could buy alcohol and give it to minors and that somebody would probably get away with it, easily.