Blood pressure
Scheer FA, Van Montfrans GA, van Someren EJ, et al. Daily nighttime melatonin reduces blood pressure in male patients with essential hypertension. Hypertension 2004;43:192-7.

Study: Researchers sought to examine whether hypertension could be lowered by better sleep.

The researchers stated: "In patients with essential hypertension, repeated bedtime melatonin intake significantly reduced nocturnal blood pressure. Future studies in larger patient group should be performed to define the characteristics of the patients who would benefit most from melatonin intake. The present study suggests that support of circadian pacemaker function may provide a new strategy in the treatment of essential hypertension."

Melatonin's Beneficial Effects on Night-Time Blood Pressure and Women Aged 47 to 63
Researchers writing in the American Journal of Hypertension examined the question: "The nocturnal decline of blood pressure (BP) is almost coincident with the elevation of melatonin, which may exert vasodilatating and hypotensive effects. In this study we investigated whether prolonged nocturnal administration of melatonin could influence the daily rhythm of BP in women."

How was the study conducted?
"In a randomized double-blind study, 18 women, 47 to 63 years of age (nine with normal blood pressure and nine being treated treated for essential hypertension) received a 3-week course of a slow-release melatonin pill (3 mg) or placebo 1 hour before going to bed. They were then crossed over to the other treatment for another 3 weeks."

What did they conclude?
"In comparison with placebo, melatonin administration did not influence (daytime) BP but did significantly decrease nocturnal systolic, diastolic, and mean BP without modifying heart rate. The effect was inversely related to the day–night difference in BP...These data indicate that prolonged administration of melatonin may improve the day–night rhythm of BP, particularly in women with a blunted nocturnal decline."

Cagnaccia A, Cannolettaa M, Renzia A, Baldassaria F, Aranginob S, Volpea A. Prolonged Melatonin Administration Decreases Nocturnal Blood Pressure in Women. American Journal of Hypertension. Volume 18, Issue 12, Pages 1614-1618

Immune Stimulation
Poon AM, Liu ZM, Pang CS, et al. Evidence for a direct action of melatonin on the immune system. Biol Signals. 1994 Mar-Apr;3(2):107-17.

From the abstract: "Pineal melatonin modulates the mammalian immune system. In vivo studies showed that melatonin enhanced the natural and acquired immunity while in vitro studies demonstrated its inhibitory influence."

Melatonin, Immune Function and Aging
Researchers writing in the medical journal Immunity & Ageing say: (From the abstract) "Aging is associated with a decline in immune function (immunosenescence), a situation (sp) known to correlate with increased incidence of cancer, infections and degenerative diseases....Melatonin has the potential therapeutic value to enhance immune function in aged individuals and in patients in an immunocompromised state."

Venkatramanujam Srinivasan, Georges J.M. Maestroni, Daniel P. Cardinali, Ana I. Esquifino, S. R. Pandi-Perumal and Sandra C. Miller. Melatonin, Immune Function and Aging. Immunity & Ageing 2005, 2:17

Read the abstract
http://www.immunityageing.com/content/2/1/17

Melatonin Randomized Trial for Insomnia in the Elderly
Nalaka S. Gooneratne, MD,MSc,  Principal Investigator,  University of Pennsylvania   
Study start: October 2004;  Expected completion: July 2007

From the study details "Melatonin is a hormone secreted predominantly during the sleep period, suspected to have a strong link to the circadian sleep-wake cycle. Melatonin is also available in a pill form and, when administered during the day, tends to have a sedative effect. Clinical trials that have examined the nocturnal effects of melatonin have focused on patients of any age who have insomnia, regardless of their endogenous melatonin levels. Data indicate, however, that individuals with low endogenous melatonin levels may be more responsive to exogenous melatonin. Generally, melatonin levels decrease with age; therefore, older individuals with insomnia represent an ideal population in which to study the effects of exogenous melatonin on sleep. This study will provide older adults with insomnia melatonin tablets to determine whether the tablets will increase their sleep."

Read more about this current research at http://clinicaltrial.gov/ct/show/NCT00230737

Melatonin and Alzheimer-like Neurodegeneration
Writing in the medical journal Acta Pharmacologica Sinica, researchers studied the effect of melatonin and cognitive impairment. They wrote: "Alzheimer disease (AD), an age-related neurodegenerative disorder with progressive loss of memory and deterioration of comprehensive cognition, is characterized by extracellular senile plaques of aggregated beta-amyloid (Abeta), and intracellular neurofibrillary tangles that contain hyperphosphorylated tau protein. Recent studies showed that melatonin, an indoleamine secreted by the pineal gland, may play an important role in aging and AD as an antioxidant and neuroprotector. Melatonin decreases during aging and patients with AD have a more profound reduction in this hormone. Data from clinical trials indicate that melatonin supplementation improves sleep, ameliorates sundowning, and slows down the progression of cognitive impairment in Alzheimer patients." Wang JZ, Wang ZF. Acta Pharmacol Sin. 2006 Jan;27(1):41-9.

Read the abstract here:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16364209

Does Melatonin Protect Vision As We Age?
Researchers writing in the Journal of Pineal Research say that Melatonin maybe beneficial in preserving visual functions.

Excerpts from the study abstract:
"Current evidence suggests that melatonin may act as a protective agent in ocular conditions such as photo-keratitis, cataract, glaucoma, retinopathy of prematurity and ischemia/reperfusion injury.

These diseases are sight-threatening and they currently remain, for the most part, untreatable. The pathogenesis of these conditions is not entirely clear but oxidative stress has been proposed as one of the causative factors.

Oxidative damage in the eye leads to apoptotic degeneration of retinal neurons and fluid accumulation. Retinal degeneration decreases visual sensitivity and even a small change in the fluid content of the cornea and crystalline lens is sufficient to disrupt ocular transparency. In the eye, melatonin is produced in the retina and in the ciliary body. Continuous regeneration of melatonin in the eye offers a frontier antioxidative defense for both the anterior and posterior eye.

However, melatonin production is minimal in newborns and its production gradually wanes in aging individuals as indicated by the large drop in circulating blood concentrations of (Melatonin).

These individuals are possibly at risk of contracting degenerative eye diseases that are free radical-based. Supplementation with melatonin, a potent antioxidant, in especially the aged population should be considered as a prophylaxis to preserve visual functions."

Siu AW, Maldonado M, Sanchez-Hidalgo M, Tan DX, Reiter RJ. Protective effects of melatonin in experimental free radical-related ocular diseases. J Pineal Res. 2006 Mar;40(2):101-9.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16441546