Light and Vitamin D
UVB exposure induces the production of vitamin D in the skin. The majority of positive health effects relate to this vitamin which has regulatory roles in calcium metabolism (which is vital for normal functioning of the nervous system, as well as for bone growth and maintenance of bone density) immunity, cell proliferation, insulin secretion and blood pressure.
"Narrowband" UVB has become the phototherapy treatment of choice for psoriasis, vitiligo, atopic dermatitis (eczema) and other photoresponsive skin disorders. Conventional Broadband UVB lamps emit light in a broad range over the UVB spectrum, including both the therapeutic wavelengths specific to the treatment of skin diseases, plus the shorter wavelengths responsible for sunburning (erythema). Sunburning has a negative therapeutic benefit, increases the risk of skin cancer, causes patient discomfort, and limits the amount of therapeutic UVB that can be taken.
"Narrowband" UVB lamps, on the other hand, emit light over a very short range of wavelengths concentrated in the therapeutic range,and minimally in the sunburning range. UVB Narrowband is therefore theoretically safer and more effective than UVB Broadband, but requires either longer treatment times or equipment with more bulbs to achieve the same dosage threshold. With the goal being to minimize the total cummulative dosage of erythemogenic ultraviolet light in a patient's lifetime, it follows that younger people should consider using UVB Narrowband. Phototherapy equipment sales are now dominated by UVB Narrowband; however, UVB Broadband will likely always have a role. Solarc's UVB Narrowband models have an "UVB-NB" suffix in the model number, such as 1780UVB-NB. Solarc's UVB Broadband models have only a "UVB" suffix, such as 1740UVB.
"Narrowband UVB" was developed by Philips Lighting of Holland and is also known as: Narrow Band UVB, UVB Narrowband, UVB-NB, NB-UVB, TL/01, TL-01, TL01, etc., (where "01" is the Philips phosphor code embedded in the bulb part number).
Understanding Narrowband UVB Phototherapy
"Narrowband" UVB (UVB-NB) has become the phototherapy treatment of choice for psoriasis, vitiligo, atopic dermatitis (eczema) and other photoresponsive skin disorders. Understanding the benefits of "Narrowband" UVB versus conventional "Broadband" UVB phototherapy requires an understanding of light and the processes it affects.
The spectrum of optical radiation (light) is made up of different wavelengths of "light" ranging from 100 nanometers (nm) in the ultraviolet (UV) range to 1 millimeter (mm) in the infrared (IR) range. Visible light spans from about 380nm (violet) to 780nm (red) and are the "colors" that we see with our eyes. Ultraviolet is invisible and ranges from 380nm down to 100nm, and is further subdivided into UVA (315-380nm), UVB (280-315nm) and UVC (100-280nm).
FIGURE A shows the relative intensities of natural "light" reaching the earth's surface after filtering by the earth's atmosphere. Humans have evolved being exposed to all these wavelengths, so our skin has developed responses to use the light beneficially(Vitamin D) and to protect us from over-exposure (tanning). "UVB Narrowband" is highlighted at 311nm and occurs naturally in sunlight, but not in great amounts. The earth's atmosphere filters nearly all light less than 290 to 300nm, depending on solar conditions.
Different wavelengths of "light" produce different effects on materials.Many important processes have been scientifically studied to determine the relative contribution of each wavelength to the studied process. Graphs known as "action spectrum" are used to describe these relationships. The greater the "action spectrum sensitivity", the more responsive is the process to that wavelength.
The action spectrum for Psoriasis has been studied 1 2 to determine that the most therapeutic wavelengths are 296 to 313 nm. Conventional UVB Broadband lamps cover this range and have been used successfully for more than 50 years. FIGURE B
The action spectrum for "sunburning" of human skin, also known as "erythema",has also been studied. 11 Erythema is dominated by the lower wavelengths (less than 300nm) of the UVB range. Unfortunately, conventional UVB Broadb and lamps produce a large amount of "light" in this erythemogenic range. These wavelengths produce burning and have less therapeutic value. What's more, it is the onset of burning limits the UVB dose3 and erythema is a major risk factor for skin cancer. Erythema also causes patient discomfort, which may discourage some patients from taking treatments. The grey shaded area in FIGURE C gives a graphical representation of the substantial erythemogenic content of UVB Broadband.
In the late 1980's, Philips Lighting of Holland developed just such a lamp,known as the "TL-01" or "UVB Narrowband" lamp. The smaller grey shaded area in FIGURE D shows that UVB Narrowband lamps have considerably less erythemogenic output (sunburning potential) than conventional UVB Broadband lamps. This means that more therapeutic UVB can be delivered before erythema occurs. And since erythema is a risk factor for skin cancer, these new lamps should theoretically be less carcinogenic for the same therapeutic results. 4 5 6 7 Furthermore, and critical to the success possible that the disease is controlled without ever reaching the erythemogenic threshold 9 10 , which was always a problem with UVB Broadband treatments. With the goal being to minimize the total cummulative dosage of erythemogenic ultraviolet light in a patient's lifetime, it follows that younger people should consider using UVB Narrowband. It is interesting to note that the peak of the UVB-Narrowband curve is about ten times higher than the UVB-Broadband curve, thus the source of the name "Narrow Band". .
More recent studies have confirmed these findings and also determined that UVB Narrowband has fewer burning incidents and longer remission periods than UVB Broadband. When compared to PUVA, UVB Narrowband has significantly fewer side effects and has replaced it in many cases. 8 UVB Narrowband is also capable of producing good therapeutic results without the patient ever eaching the erythemogenic threshold.
One disadvantage of UVB Narrowband is that, because the maximum dosage is limited by the onset of slight erythema, and UVB Narrowband is less erythemogenic than UVB Broadband, longer treatmenttimes are required. This can be compensated by increasing the number of bulbs in the device. 4 5 6 7 For instance, based on Solarc's home phototherapy after sales follow-ups ,for UVB Broadband the 4-bulb 1740UVB provides reasonable treatment times; whereas for UVB Narrowband, the 8-bulb 1780UVB-NB is the preference. (For skin types I to III; which is generally white caucasions.) The theoretical ratio of erythemogenic potential of UVB-Broadband to UVB-Narrowband is in the range of 4:1 to 5:1.
Other diseases such as vitiligo, mycosis fungoides (CTCL), and many others have also been successfully treated with UVB Narrowband, generally for the same reasons as described above for psoriasis.
Another very interesting benefit of UVB-Narrowband is that it is likely the best fluorescent lamp type for making Vitamin D (FIGURE E) in human skin, for possible use as a substitute for UVB in natural sunlight. The subject of Vitamin D has received tremendous media attention lately, and for good reason.Vitamin D is essential to human health for its role as a catalyst for calcium absorption, yet many people are deficient, especially those that live at higher latitudes, far away from the earth's equator. There is increasing evidence that Vitamin D protects against the development of many chronic diseases,including: cancer (breast, colorectal, prostate), cardiovascular disease,multiple sclerosis, osteomalacia, osteoporosis, type 1 diabetes mellitus, rheumatoid arthritis, hypertension, and depression. For much more information, please visit these webpages:
The prevailing opinion in the dermatology community is that UVB Narrowband will largely replace UVB Broadband as a treatment option,especially for home phototherapy. This is clearly supported by Solarc Systems' trend in home phototherapy equipment sales, with the sales of UVB-NB devices now outpacing UVB-BB sales by about 50:1. However, UVB Broadband will likely always have a role. Solarc's UVB Narrowband models have an "UVB-NB" suffix in the model number, such as 1780UVB-NB. Solarc's UVBBroadband models have only a "UVB" suffix,such as 1740UVB.
Solarc Systems would like to thank the good people at Philips Lighting for developing the UVB-Narrowband product line, and helping so many of us worldwide manage our skin problems safely and efficiently.
Note: The figures used in this document are simplified representations. The UVB Broadband curve is derived from the Solarc/SolRx 1740UVB and the UVB Narrowband curve is derived from the Solarc/SolRx 1760UVB-NB.