A speculative journalistic investigation of the phenomenon where two people who loved each other have died in short proximity:
Evans, S. (2016). Can you die from a broken heart? London: BBC Health News / BBC News Magazine, December 29th 2016.
Death By Statistics…
The statistical analyses, probably more of interest to experts:
Shor, E. Roelfs, DJ. [and] Curreli, M. [et al] (2012). Widowhood and mortality: a meta-analysis and meta-regression. Demography. May 2012; 49(2): 575-606.
Moon, JR. Kondo, N. [and] Glymour, MM. [et al] (2011). Widowhood and mortality: a meta-analysis. PLoS One. 2011; 6(8): e23465.
Regarding cardiovascular risks in particular:
Carey, IM. Shah, SM. [and] DeWilde, S. [et al] (2016). Increased risk of acute cardiovascular events after partner bereavement: a matched cohort study. JAMA Internal Medicine. April 2014; 174(4): 598-605.