The ESTxENDS Trial- Substudy on the Effects of Using Electronic Nicotine Delivery Systems (ENDS) on Sleep Quality.

Exclusion Criteria

• •Known hypersensitivity or allergy to contents of the e-liquid
• •Participation in another study with investigational drug within the 30 days preceding the baseline visit and during the present study where interactions are to be expected
• •Women who are pregnant or breast feeding
• •Intention to become pregnant during the course of the scheduled study intervention, i.e. within the first 6-months of the study
• •Persons having used ENDS or tobacco heating systems regularly in the 3 months preceding the baseline visit
• •Persons having used nicotine replacement therapy (NRT) or other medications with demonstrated efficacy as an aid for smoking cessation such as varenicline or bupropion within the 3 months preceding the baseline visit
• •Persons who cannot attend the 6- month follow-up visit for any reason
• •Cannot understand instructions delivered in person or by phone, or otherwise unable to participate in study procedures