Factors affecting life expectancy include access to and the quality of health care, genetics, living conditions, hygiene, and diet. Scientists are still debating the relative importance of these factors in determining life expectancy, as of 2015.
Medical breakthroughs and the increased quality of health care in recent decades are major reasons for the massive increases in the life expectancy in developed countries over the last century. Individuals' access to good quality health care is thus very important in determining their life expectancy. Interestingly, the effect on life expectancy is about the same for preventative treatments as for therapeutic treatments.
Where hygiene standards improve, so does life expectancy. Hygiene improvements may involve changing societal norms and improved sanitation infrastructure.
An individual's genetics is also an important consideration in their life span, with the conclusion that we, in part, inherit our life span. Another poorly understood factor affecting life span is gender, with woman living approximately seven years longer than men in almost all societies around the world.
Better diet and lifestyle are also important factors with regards to life expectancy. While there are many studies showing that these factors contribute to a person's life expectancy, disagreement remains over the relative importance of the different contributing factors.