Investigating the Effects of Evening Light Exposure on Melatonin Suppression, Alertness and Nocturnal Sleep

Inclusion Criteria:

(i) Aged between 18-30 years to reduce the confounding effects of lens aging on the transmission of light to the retina;

(ii) Non-smoking for at least 6 months;

(iii) Healthy (no medical, psychiatric or sleep disorders);

(iv) No clinically significant deviations from normal in medical history, vital signs, physical examination, blood chemistry and hematology, urine chemistry and ECG;

(v) Women of childbearing potential must agree to use an acceptable method of birth control, and must have a negative urine pregnancy test;

(vi) Body mass index of > 18 or < 30 kg/m2;

(vii) No drugs or medication likely to affect sleep or alertness, as determined by the investigators;

(viii) Habitual caffeine consumption < 300mg per day on average;

(ix) Habitual alcohol consumption < 10 alcoholic units per week on average.

Exclusion Criteria:

(i) History of alcohol or substance abuse;

(ii) Positive result on drugs of abuse screening;

(iii) Current or past history of sleep disorders, including but not limited to obstructive sleep apnea, or any significant sleep complaint;

(iv) Psychiatric disorder;

(v) Recent acute or chronic medical disorder, including but not limited to hepatic impairment and severe chronic obstructive pulmonary disease;

(vi) Visual disorder, including but not limited to color blindness, or family history of glaucoma;

(vii) History of intolerance or hypersensitivity to melatonin or melatonin agonists;

(viii) Pregnancy or lactation;

(ix) Shift work;

(x) Transmeridian travel (2 or more time zones) in past 2 months;

(xi) Any other reason as determined by the Principal Investigator.