Please select the eligibility criteria that correspond to the clinical trial below.
Title: Vascular Effects of Regular Cigarettes Versus electronIc Cigarette Use
Brief Summary: The purpose of this study is to assess the effects of electronic cigarettes-nicotine and electronic cigarette-nicotine free on endothelial function as compared to traditional cigarettes. Due to ethical reasons, we cannot fully randomise all particpants to the three arms.

Participants who wish to quit smoking will be randomized to

1. Switch to electronic cigarettes containing nicotine plus flavor
2. Switch to electronic cigarettes containing flavor alone Those who do not wish to quit smoking will continue on the Tobacco Cigarette arm Treatment period will be 28 days


Options:
A: Inclusion Criteria:

Subjects must meet all of the following inclusion criteria to be eligible for enrolment into the study:

1. Able to comply with the study procedures
2. Male or female healthy smokers aged ≥19
3. Smoking at least 10 cigarettes a day
4. Smoking for at least one year
5. Not currently attempting to quit smoking or wishing to do so in the next 30 days (this will be verified at screening by the answer ''NO'' to both questions ''Do you intend to quit in the next 30 days?'' and ''Are you interested in taking part in one of our smoking cessation programs?'')
6. Female smokers not planning to become pregnant are using an acceptable form of contraception.

Exclusion Criteria:

The presence of any of the following will exclude a subject from study enrolment:

1. Use of smokeless tobacco, or any other tobacco products (including e-cigarettes, cigars, chewing tobacco, snus, etc.) within the last 3 months, at baseline and during the whole study.
2. Use of nicotine replacement therapy or other smoking cessation therapies within the last 3 months and at baseline.
3. Self-reported pregnancy, planned pregnancy or breastfeeding.
4. Tobacco industry employees and 1st degree relatives will be excluded in order to safeguard independence of the study

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B: Inclusion Criteria:

* Age 21-65
* Smoke \>9 cigarettes per day for at least 1 year
* Smoke regular filtered cigarettes or machine-rolled cigarettes with a filter
* CO measurement \>9 ppm at baseline
* No serious quit attempt in the prior 1 month. This includes use of any FDA approved smoking cessation medication (varenicline, bupropion \[used specifically as a quitting aid\], patch, gum, lozenge, inhaler, and nasal spray) in the past 1 month as an indication of treatment seeking.
* Not planning to quit in the next 6 months
* Interested in reducing cigarette consumption
* Willing to attend visits weekly and monthly over a 9-month period (not planning to move, not planning extended vacation, no planned surgeries)
* Read and write in English
* Able to understand and consent

Exclusion Criteria:

* Pregnant and/or nursing women
* Unstable or significant medical condition in the past 12 months (Recent heart attack or some other heart conditions, stroke, severe angina including high blood pressure if systolic \>159 or diastolic \>99 observed during screening).
* Immune system disorders, respiratory diseases (exacerbations of asthma or COPD, require oxygen, require oral prednisone), kidney (dialysis) or liver diseases (cirrhosis), or any medical disorder/medication that may affect participant safety or biomarker data.
* Use of any non-cigarette nicotine delivery product (pipe, cigar, dip, chew, snus, hookah, ECIGs, strips, sticks) in the past 7 days
* Uncontrolled mental illness or substance abuse or inpatient treatment for these in the past 6 months
* History of difficulty providing or unwilling to provide blood samples (fainting, poor veins, anxiety)
* No surgery requiring general anesthesia in the past 6 weeks
* Use of an ECIG for 5 or more days in the past 28 days or any use in the past 7 days
* Use of marijuana or any illicit drug/prescription drugs for non-medical use daily/almost daily, or weekly in the past 3 months per NIDA Quick Screen
* Use of hand-rolled, roll your own cigarettes
* Known allergy to propylene glycol or vegetable glycerin
* Other member of household is currently participating/participated in the study
C: Inclusion Criteria:

* Participants (N=1100) will be men and women 18 years of age and older, recruited from four acute inpatient psychiatry units at the Alta Bates Summit Medical Center - Herrick Campus, located in Berkeley, CA, one acute inpatient psychiatry unit at Langley Porter Psychiatric Institute, located in San Francisco, CA, and two acute inpatient psychiatry units at Stanford Hospital, located in Stanford, CA. Inclusion criteria are: smoking 5 or more cigarettes per day and at least 100 cigarettes in one's lifetime, no plan to relocate outside of the greater Bay Area in the next 18 months, and telephone access for scheduling follow-up assessments.

Exclusion Criteria:

* Study exclusion criteria are: dementia or other brain injury precluding ability to participate; non-English speaking; complete homelessness; pregnancy or breastfeeding, and active ulcer disease (PUD). The relationship between nicotine and ulcers is a theoretical concern and our approach to now exclude patients with active ulcer disease is conservative. There is no data to show NRT causes/worsens ulcers. Recruitment of acutely psychotic, manic, or hostile patients will be delayed until there is significant reduction of these symptoms and patients are able to consent to study participation. Threats of violence in particular are taken seriously, and patients will not be recruited if they may be a threat to study staff in the outpatient setting. At this point, non-English measurement and intervention materials are not available. Pregnant smokers will be referred out for more specialized behavioral treatments. Exclusionary criteria are purposefully minimal in order to maximize information about treating tobacco dependence in smokers in inpatient psychiatry. The study sample is anticipated to be diverse with respect to gender and ethnicity, educational and socioeconomic level, and psychiatric diagnoses.
D: Inclusion Criteria:

* Aged 18 years and over
* Currently smoking ≥15 full strength tobacco cigarettes per day for at least 2 years, or roll-up tobacco equivalent (cigar or pipe smokers not included).
* Willing to stop tobacco cigarettes for period of study if required
* Willing not to use electronic cigarettes if required
* Able to give informed consent

Exclusion Criteria:

* Pregnant or lactating.
* Women of childbearing potential who do not abstain from sex or use effective contraception.
* On current prescribed medication for cardiovascular disease.
* History of cardiovascular disease (excluding hypertension), diabetes, active malignance or chronic renal disease.
* Nut allergy
* Participation in another clinical trial (other than observational trials and registries) with an investigational product and/or intervention within 30 days before visit 1.

Answer: D