"These observational studies were unable to determine whether insomnia is a cause, or if it is just associated with them," said the study's lead author Susanna Larsson, Associate Professor at the Karolinska Institute in Sweden.
In the study, the researchers applied Mendelian randomisation, a technique that uses genetic variants known to be connected with a potential risk factor, such as insomnia, to reduce bias in the results.
The 1.3 million participants with or without heart disease and stroke were drawn from four major public studies and groups, said the research published in the journal Circulation.
Researchers found genetic variants for insomnia were associated with significantly higher odds of coronary artery disease, heart failure and ischemic stroke - particularly large artery stroke.
"It is important to identify the underlying reason for insomnia and treat it.
"Sleep is a behaviour that can be changed by new habits and stress management," Larsson said.
A limitation to the study is that the results represent a genetic variant link to insomnia rather than insomnia itself.