Supplementation of vitamin D is effective in preventing overall mortality in a long-term. It is not significantly effective in a treatment duration shorter than 3 years. 

Vitamin D therapy significantly decreased all-cause mortality with a duration of follow-up longer than 3 years. No benefit was seen in a shorter follow-up periods. 

The following subgroups of long-term follow-up had significantly fewer deaths:

• female only,
• participants with a mean age younger than 80,
• daily dose of 800 IU or less,
• participants with vitamin D insufficiency and cholecalciferol therapy.

The combination of vitamin D and calcium significantly reduced mortality and vitamin D alone also had a trend to decrease mortality in a longer time follow up.