Is this true? Is there an explanation for this?
Again a study done in 1980 by Halpern & Coren implied that left-handed people had an average life expectancy of 9 years less than right-handed people. However, the data was not considered credible since it was based only on second-hand information gathered from the next-of-kin of recently deceased persons who were right and left-handed. The findings of researchers revealed that left-handed average age of death was 66 and the right-handed average age was 75.
However, that second-hand survey data used in the Halpern & Coren study is not a reliable methodology and only a few number of sample sizes were used. The research made by Aggleton, Bland, Kentridge, & Neave in the British Medical Journal does not agree on the theory that left-handed people die earlier.
But there are some evidences that left-handed women may have a shorter life span than right-handed women. A recent Dutch study indicated that left-handed women had a 40 percent higher risk of dying from any cause. They have a 70 percent higher risk of dying from cancer, and a 30 percent higher risk of dying from diseases of the circulatory system. Left-handed women also had a 2 times increased risk of dying from breast cancer, close to a 5 times increased risk of dying from colorectal cancer, and more than 3 times higher risk of cerebro-vascular mortality.
So that "fact" was based on the results of the study in bold.