Idiomas:
The SCENIHR opinion states:
Flicker can induce migrane
Source: Bob Smith3.5. Potential mechanisms for impact on users
3.5.1. Effects of fluorescence light vs. normal incandescent light on non-skin pre-existing conditions
Here we discuss the influence of flicker, blue light, “light” in general, and EMF, as emanating from conventional and compact fluorescence lamps on non-skin related pre-existing conditions. The various conditions are discussed separately and the possible influence of the physical factors is evaluated using the criteria outlined in section 3.2.
3.5.1.1. Epilepsy
Five percent of the total world population has single seizures, and the annual incidence is 50 in 100.000 (WHO 2001). About 5 in 100 of epileptic people have photosensitive epilepsy (Epilepsy Action 2007). Photosensitive epilepsy is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns. Often persons with photosensitive epilepsy have no history of seizures outside of those triggered by visual stimuli.
The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing or flickering lights or rapidly changing or alternating images are an example of patterns in time that can trigger seizures (Harding et al. 2005). Epilepsy Action (2007) states that fluorescent lights should normally not cause a problem, except for faulty lamps, which may flicker at a lower frequency. However, much higher risks are connected with television and video games.
While photosensitivity of epileptics is scientifically proven (Steinkruger 1985, Wilkins et al. 1999, Wilkins et al. 2004), it is not analyzed if the flicker frequency range > 120 Hz causes seizures, as do frequencies of 15 – 18 Hz (Hughes 2008) and of 3 Hz (Harding et al. 2005). Although an old study of flicker (50 and 100 Hz) from fluorescent lighting with aging lamps did not suggest a hazard to photosensitive patients (Binnie et al. 1979), a more recent study reports that flicker from screens with 50 Hz repetition frequency causes discharges in the investigated subjects, whereas 100 Hz screens appear to be safe (Ricci et al. 1998).
Conclusion
Seizures are induced by flicker but can be accurately correlated to the frequency only for a small range (3 Hz, 15 – 18 Hz) [Evidence level A]. There is no scientific evidence that fluorescent lamps including CFL induce seizures [Evidence level E].
3.5.1.2. Migraine
As defined on the website of the National Institute of Neurological Disorders and Stroke, migraine is an intense pulsing or throbbing pain in one area of the head. It is often accompanied by extreme sensitivity to light and sound, nausea, and vomiting. Migraine is three times more common in women than in men. Some individuals can predict the onset of a migraine because it is preceded by an "aura," visual disturbances that appear as flashing lights, zig-zag lines or a temporary loss of vision. People with migraine tend to have recurring attacks triggered by a lack of food or sleep, exposure to light, or hormonal irregularities (only in women). Anxiety, stress, or relaxation after stress can also be triggers. For many years, scientists believed that migraines were linked to the dilation and constriction of blood vessels in the head. Investigators now believe that migraine is caused by inherited abnormalities in genes that control the activities of certain cell populations in the brain (National Institute of Neurological Disorders and Stroke, 2008).
It is estimated that 14% of the adults in Europe have migraine (Stovner et al. 2006). According to self-reported information, certain visual patterns can reliably trigger a migraine attack, such as high contrast striped patterns or flickering lights (Shepherd 2000).
Fluorescent lamps can cause eye-strain and headache (Wilkins et al. 1991). Patients with migraine show somewhat lowered flicker fusion thresholds during migraine-free periods (Kowacs et al. 2004). In addition, photophobia, which is an abnormal perceptual sensitivity to light experienced by most patients with headache during and also between attacks, is documented in many studies (Main et al. 2000).
People with migraine claim to be particularly sensitive to blue light (European Lamp Companies Federation).
Conclusion:
Migraine can be induced by flicker in general (up to about 50 Hz) and patients are light sensitive during and between attacks [Evidence level A]. Scientific support for aggravating symptoms by flicker from fluorescent tubes was not found [Evidence level D]. There is anecdotal evidence of problems with blue light [Evidence level D].
3.5.1.3. Irlen-Meares (Dyslexia; Scotopic Syndrome)
Irlen-Meares is a learning disability that manifests itself primarily as a difficulty with reading and spelling which may be improved by use of coloured lens or overlays. The Irlen-Meares syndrome is also known as Meares-Irlen syndrome and closely linked to Scotopic Syndrome. There is no consensus reached within the scientific community about its actual distinctiveness from other forms of dyslexia. It is separate and distinct from reading difficulties resulting from other causes, such as non-neurological deficiency with vision or hearing, or from inadequate reading instruction. Evidence also suggests that dyslexia results from differences in how the brain processes written and/or spoken language. Although dyslexia has a neurological basis, it is not an intellectual disability.
Dyslexia occurs at all levels of intelligence and causes fatigue, headache and word- scrambling, and is considered a learning disability. Dyslectics show impaired flicker detection at 10 Hz (Evans et al. 1994) and do not react uniformly to a flickering stimulus (5, 10, 15, 20, and 25 Hz) (Ridder et al. 1997).
Irlen-Meares is a problem associated with the brain's ability to process visual information. The scientific literature, however, states that due to a deficit in the visual magnocellular pathway, impaired sensitivity to both drifting and flickering gratings exist (Ben-Yehudah et al. 2001), as well as to flickering or moving visual stimuli (Cornelissen et al. 1998).
Self-reporting suggests that fluorescence lighting in contrast to incandescent light aggravate the symptoms of dyslexia. Probably the main problems are caused by UV radiation and blue light, emitted by cool white tubes (Irlen method 2008).
Conclusion:
It is has been shown that dyslectics and Irlen-Meares patients tend to have difficulties detecting flicker. Therefore, flicker from fluorescent tubes should not be a problem [Evidence level A]. There are self-reported indications that the condition is aggravated by mainly UV and blue light [Evidence level D].
3.5.1.4. Ménière’s Disease
Ménière’s disease is a disorder of the inner ear. Although the cause is unknown, it probably results from an abnormality in the fluids of the inner ear. Ménière’s disease is one of the most common causes of dizziness originating in the inner ear. In most cases only one ear is involved, but both ears are affected in about 15 percent of patients.
The symptoms of Ménière’s disease are episodic rotational vertigo (attacks of a spinning sensation), hearing loss, tinnitus (a roaring, buzzing, or ringing sound in the ear), and a sensation of fullness in the affected ear. Tinnitus and fullness of the ear in Ménière’s disease may come and go with concomitant changes in hearing, occur during or just before attacks, or be constant. There may also be an intermittent hearing loss early in the disease, especially in the low pitches, but a fixed hearing loss involving tones of all pitches commonly develops in time. Loud sounds may be uncomfortable and seem distorted in the affected ear. From all the Ménière’s disease’s symptoms, vertigo is usually the most troublesome. Vertigo may last for 20 minutes to two hours or longer. During attacks, patients are usually unable to perform activities normal to their work or home life. Sleepiness may follow for several hours, and the off-balance sensation may last for days. The symptoms of Ménière’s disease may be only a minor nuisance, or can become disabling, especially if the attacks of vertigo are severe, frequent, and occur without warning (Ménière’s disease 2008). Increased sensitivity to physical stimuli like flickering or fluorescent lights during the attacks of Ménière’s disease (e.g. vertigo) is self-reported (Vestibular Disorder Association 2005). A recommendation for vertigo is to provide an alternative to fluorescent lighting (Job Accommodation Network 2005).
Conclusion:
Light conditions are not associated with Meniere’s disease. However, the attacks may be aggravated by flicker [Evidence level D].
3.5.1.5. HIV/AIDS
The Human immunodeficiency virus (HIV) is a retrovirus that kills the T-helper cells which are essential components of the human body's immune system. Therefore, HIV decreases the ability of the body to fight infection and disease which usually leads to the development of the so-called acquired immunodeficiency syndrome (AIDS).
HIV-positive persons with retinal damage (see the Retina diseases section below) have been shown in one study to have increased sensitivity to flickering light (Plummer et al. 1998). Problems with fluorescent tubes are not reported.
Conclusion:
No risk from flicker concerning other symptoms than retinal diseases has been found for HIV-positive persons [Evidence level E].
3.5.1.6. Retinal diseases
Photochemical damage from blue light may induce several harmful effects to the retina mainly by the production of singlet oxygen (Rózanowska et al. 1995, 1998). Therefore filters are recommended to protect lens and retina from blue light (Ham 1983), if the antioxidant defence mechanisms and the presence of melanin cannot protect against the damage (Sarna et al. 2003). HIV-positive patients may have retinal damage such as infectious retinopathies and noninfectious complications, which makes them more sensitive to blue light (Plummer et al. 1998).
Conclusion:
Blue light may be harmful to those with retinal diseases [Evidence level B]. There is also some evidence that prolonged exposure to blue light may reduce the colour sensitivity of the intact retina [Evidence level B].
3.5.1.7. Autism/Aspergers Syndrome
Autism is a neuro-developmental disorder characterized by deficiencies in social interactions and communication skills, as well as repetitive and stereotyped patterns of behavior. Recent epidemiological data show that autism is a frequent disorder, observed in 1 child in 500. The cumulated prevalence of diseases belonging to the spectrum of autism (autism, Aspergers syndrome) and pervasive developmental disorders not otherwise specified, has been estimated at 1/167 (Orphanet 2008).
The studies of Colman et al. (1976), which suggested that repetitive behavior can be aggravated by the flickering nature of fluorescent illumination, had interpretative problems and could not be replicated (Turner 1999). However, a putative relationship between autism and migraine is still suggested by similarities between the two conditions, including the presence of sensory over-stimulation (Casanova 2008). This suggestion is however made without any further investigation into the importance of flicker.
Conclusion:
There is no evidence showing negative effects of fluorescence light on autistic behavior, however, an influence cannot be excluded [Evidence level D].
3.5.1.8. Myalgic encephalomyelitis (Chronic Fatigue Syndrome)
Chronic fatigue syndrome is one of several names given to a potentially debilitating disorder characterized by profound fatigue which lasts for at least six months. It has a prevalence that varies from 0.2% to above 2% (Wyller 2007). According to the US Centers for Disease Control and Prevention, persons with chronic fatigue syndrome most often function at a substantially lower level of activity than they were capable of before the onset of illness. In addition to these key defining characteristics, patients report various nonspecific symptoms, including weakness, muscle pain, impaired memory and/or mental concentration, insomnia, and post-exertional fatigue lasting more than 24 hours. In some cases, CFS can persist for years. The cause or causes of CFS have not been identified and no specific diagnostic tests are available (Centers for Disease Control and Prevention, 2008) A number of illnesses have been described that have a similar spectrum of symptoms to CFS. These include fibromyalgia syndrome, myalgic encephalomyelitis, neurasthenia, multiple chemical sensitivities, and chronic mononucleosis.
According to self-reporting, about 52,500 people in the UK (= 21% of myalgic encephalomyelitis) have increased sensitivity to light (Action for M. E. 2008). Patient studies have also indicated excessive light sensitivity (Söderlund et al. 2000). This is in contrast to other studies, where reduced sensitivity towards sunny, dry, and long days compared to controls can be found (García-Borreguero et al. 1998), and which suggested a disturbance of the biological clock (Durlach et al. 2002).
Conclusion:
There is conflicting evidence regarding patient’s sensitivity towards light. Symptoms may be aggravated by many factors, including light conditions as stated by self-reporting [Evidence level D]. There is no evidence for a link between chronic fatigue syndrome and fluorescent lighting [Evidence level E].
3.5.1.9. Fibromyalgia
According to the National Institute of Arthritis and Muscoloskeletal and Skin Diseases, Fibromyalgia is a disorder that causes muscle pain and fatigue (feeling tired). People with fibromyalgia have “tender points” on the body. Tender points are specific places on the neck, shoulders, back, hips, arms, and legs. These points hurt when pressure is put on them. People with fibromyalgia may also have other symptoms, such as: trouble sleeping; morning stiffness; headaches; painful menstrual periods; tingling or numbness in hands and feet; and problems with thinking and memory (sometimes called “fibro fog”) (National Institute of Arthritis and Muscoloskeletal and Skin Diseases, 2007).
Conclusion:
Light conditions do not play a role in fibromyalgia [Evidence level A]. Problems with fluorescent lamps are not investigated but are very unlikely [Evidence level E].
3.5.1.10. Dyspraxia (apraxia)
Developmental dyspraxia is a developmental (e.g. spastic) coordination disorder which is a life-long condition that is more common in males than in females; the exact proportion of people with the disorder is unknown since the disorder is hard to detect. Current estimates range from 5% - 20% with at least 2% being affected severely.
Conclusion:
No evidence in the scientific literature is found regarding any influence of light conditions on dyspraxia [Evidence level E].
3.5.1.11. Photophobia
Photophobia is eye discomfort in bright light, which occurs in many diseases including migraine (see above). Photophobia is a symptom most often associated with pathological eye conditions such as cataracts, corneal damage, burns, infections, inflammation, injury, retinal detachment, etc. People with lighter-coloured eyes and albinism often suffer from photophobia. Since only general studies about effects of light are found, it is concluded that the main problem is the light intensity; irrespective of modulation of other light parameters.
Conclusion:
Any effect of flicker, blue light and fluorescent tubes has not been investigated, but cannot be ruled out [Evidence level C].
3.5.1.12. UV radiation, snow-blindness and cataract
With adequate blocking of UVC and UVB radiation, the CFL do not pose a risk for inducing snow-blindness (sunburn on the exposed surface of the eye ball). However, recent measurements (see section 3.4.) show that some commercially available CFL emit traces of UVC and significant amounts of UVB radiation, which could conceivably cause snow- blindness if the lamp is in close proximity to the eye for an extended period of time (the eye is far more sensitive to UVC radiation than the skin). However, preliminary measurements (personal communication De Gruijl) showed that threshold limits are not easily exceeded. Long-term exposure of the eye to UV radiation (wavelengths lower than 320 nm) may contribute to cataract formation (opacity of the lens). With overhead positioning of lamps this should not pose a significant risk in comparison to sun exposure, but with UV emitting lamps at eye level contributions may become important.
There are no indications that fluorescent tubes used in room illumination cause either snow-blindness or cataract.
Conclusion:
Fluorescent light does not cause snow-blindness [Evidence level B] or cataract [Evidence level C]. This holds true for CFL, provided that UVC and UVB radiations are adequately filtered out.
3.5.1.13. Electromagnetic hypersensitivity
An in-depth description of the characteristics and occurrence of EMF, as well as the current view on possible health effects after exposure to these EMF can be found in the SCENIHR Opinion: Possible effects of electromagnetic fields (EMF) on human health (SCENIHR, 2007). The limit of exposure to the general public from EMF is based on guidelines by the International Committee on Non Ionising Radiation Protection (ICNIRP, 1998). In short, the levels are frequency dependent and set to avoid acute harmful effects, which in the low frequency part of the spectrum may lead to nerve excitation, and in the radio frequency part of the spectrum tissue heating.
There have been claims that the electromagnetic fields (EMF) emitted from CFL could cause symptoms among persons that consider themselves sensitive to CFL. Furthermore, it has also been reported that persons experiencing symptoms from mobile phones are also “sensitive” to CFL. The subjective symptoms that are mentioned include dermatological symptoms like reddening, tingling and burning sensations, but also headache, fatigue, dizziness, concentration difficulties and nausea. The question is thus if these symptoms can be triggered by EMF, and if CFL irradiate such EMF.
Those that attribute specific health problems like the ones mentioned above to any kind of EMF are often termed “electromagnetic hypersensitive” (WHO 2005). This refers to exposure to extremely low frequency (ELF) electromagnetic fields, as well as to fields of the high frequency kind. The former fields are typically generated from power lines and from various electric devices. Examples of high frequency fields are the fields emitted from devices used for mobile communication (mobile phones and their base stations). These fields have frequency components that belong to the so called radiofrequency part of the spectrum (RF fields).
The symptoms that are attributed to ELF and to RF fields are similar. Many patients also claim that both types of exposure trigger their symptoms. The question whether there exists a real correlation between exposure to EMF and the reported symptoms has been studied in epidemiological studies as well as in provocation studies. The former studies allow for finding possible statistical connections between field exposure and long-term, chronic effects, whereas the provocation studies can reveal if there are any immediate effects by a specific type of exposure. There are a number of published provocation studies, mostly on ELF fields, but also on RF fields to an extent. Recent extensive reviews of these studies clearly show that there is no connection between acute EMF exposure (ELF and RF) and perceived symptoms (WHO 2005, Seitz et al. 2004, Rubin et al. 2005, Röösli 2008). However, these studies do not contribute knowledge regarding any long- term effect. There are few studies with appropriate methodology that address long-term effects of RF exposure and symptoms, whereas a somewhat higher number of studies have focused on ELF effects on symptoms. Most studies have not found any correlation between exposure and symptoms. One RF study related to base stations was performed by Hutter et al. (2006) who found a connection between exposure to higher power densities (1.3 mW/m2) and some, but not all, of the investigated self-reported symptoms.
The literature on the kinds and strength of EMF that are emitted from CFL is sparse. However, there are several kinds of EMF found in the vicinity of these lamps. Like other devices that are dependent on electricity for their functions, they emit electric and magnetic fields in the ELF range (mainly 50 Hz in Europe). In addition, CFL, in contrast to the incandescent light bulbs, also emit in the high frequency range (30-60 kHz). These frequencies differ between different types of lamps. A Swiss study (Bundesamt für Energie, 2004), is one of the few available studies where correct measurements of CFL and their EMF have been performed. In this work, eleven different energy saving lamps were investigated and compared with two types of ordinary incandescent light bulbs. All measured values were far below any limits set by guidelines of international organizations like ICNIRP.
The 50 Hz magnetic field that was measured 30 cm from the lamps was in the nT range, which is very low and comparable to the background fields in any room without electric appliances that are using strong electric currents. The high frequency magnetic fields differed to some extent between different types of lamps, but were still in the nT range 30 cm from the source.
The 50 Hz electric field was also measured and found to be somewhat higher in CFL than from normal lamps, but lower than from other electric appliances. Finally, the high frequency electric fields (which are not present from incandescent bulbs) are measurable but at very low intensity.
Conclusion:
Although there is scarce literature in the area, it seems that the electromagnetic fields generated from CFL are not unique to these lamps, and also not strong in comparison with EMF from any other devices. It has never been conclusively and convincingly shown that there exist any connections between EMF and the symptoms that are reported by persons with so-called electromagnetic hypersensitivity, although their symptoms are real and in many cases very severe. Thus, based on current scientific knowledge, there do not seem to be any correlation between EMF from CFL, and symptoms and disease states [Evidence level A].
3.5.1.14. Conclusions regarding non-skin pre-existing conditions
There are several self-reported statements about adverse health effects of fluorescent lamps, partly based on subjective perception and psychological effects and lacking scientific evidence. There is a need for additional experimental and epidemiological studies before final conclusions can be drawn regarding several of the conditions that are mentioned in the mandate for this Opinion.
There is evidence showing that flicker can cause seizures in patients with photosensitive epilepsy [Evidence level A], although there are no reported effects of CFL having such effects [Evidence level E].
Migraine can be induced by flicker [Evidence level A], but no evidence has been provided that CFL do that [Evidence level E].
Blue light can aggravate retinal diseases in susceptible patients [Evidence level B], or possibly aggravate migraine [Evidence level D].
It cannot be excluded that Photophobia is induced or aggravated by different light conditions, but it is not even mentioned in self-reports [Evidence level C].
People with Autism/Aspergers syndrome have reported problems which they attributed to fluorescent lighting.
There is sufficient evidence [Evidence level A] that the conditions of patients with Irlen- Meares syndrome are not influenced by CFL. No reported effects [Evidence level E] indicate that symptoms in patients with ME, fibromyalgia, dyspraxia, and HIV would be aggravated by CFL.
It is unlikely that fluorescent lamps can cause snow-blindness or cataracts [Evidence levels B, C].
It is unlikely that any EMF emitted from CFL or other fluorescent lamps would contribute to electromagnetic hypersensitivity [Evidence level A].
However, any possible health problems related to flicker and UV/blue light emission are minimized, if CFL are equipped with functional high-frequency electronic ballasts, double envelopes and adequate coating.
Source & ©:
3. Scientific Rationale, Section 3.5. Potential mechanisms
for impact on users, Subsection 3.5.1. Effects of fluorescence light
vs. normal incandescent light on non-skin pre-existing conditions p.
16 – 23
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