The authors wrote in their background information that there was very little research on any potential link between coffee consumption and stroke risk.

For this study, Lopez-Garcia and colleagues analyzed data from the Nurses’ Health Study. The data covered 83,076 women who were followed for 24 years, starting with the first assessment of coffee consumption in 1980. This assessment was repeated every 2 to 4 years until 2004.

None of the women had a history of stroke, coronary heart disease, diabetes, or cancer at the start of the study.

The main outcome measure was the number and type of strokes that occurred among the women during the follow up.

Using statistical tools like Cox regression models, the researchers analyzed the relative risks (RR) between the stroke events and coffee consumption, while ruling out potential confounders such as age, smoking status, body mass index (BMI), exercise/physical activity, use of alcohol, menopausal status, use of hormone therapy, use of aspirin, and other dietary factors.

The results showed that:

* Over the follow up period, there were 2,280 strokes: 426 of which were hemorrhagic (burst blood vessel in the brain), 1,224 ischemic (loss of blood supply to the brain), and 630 undetermined.

* The relative risk of stroke went down as coffee consumption went up.

* For women who drank between 1 cup of coffee a month and 4 cups per week, the relative risk of stroke was 0.98 compared to women who drank less than one cup a month.

* For women who drank 5 to 7 cups of coffee a week, the relative risk of stroke was 0.88.

* For 2 to 3 cups a day the relative risk was 0.81, and for more than 4 per day it was 0.80.

* After adjusting the figures again to take into account high blood pressure, high blood cholesterol and type 2 diabetes, the relative risk of stroke still showed the same inverse association with coffee consumption: it went down as coffee consumption went up.

* The association was stronger among women who had either never smoked or had given up than among current smokers .

* Stroke risk was not linked to consumption of other drinks containing caffeine such as tea and caffeinated soft drinks.

* After taking out the effect of caffeinated coffee drinking, increasing decaffeinated coffee consumption was also found to be linked to lower stroke risk (relative risk of 2 or more cups a day compared to less than 1 a month was 0.89).

The authors concluded that:

“Long-term coffee consumption was not associated with an increased risk of stroke in women. In contrast, our data suggest that coffee consumption may modestly reduce risk of stroke.”

It would appear from these results that the beneficial link is not due to caffeine. WebMD reported that Lopez-Garcia suggested it was other ingredients in coffee that may be responsible for the lower risk of stroke as consumption rises:

“Antioxidants in coffee lower inflammation and improve blood vessel function,” she said in a press statement.

However, Lopez-Garcia cautioned that the beneficial effect of coffee drinking only applies to healthy people. Increasing coffee consumption will not make existing stroke risk from other causes go away.

And anyone with health problems should talk to their doctor about their own specific risk, she said. For instance people suffering with blood pressure, heart problems, anxiety or insomnia may not benefit from drinking coffee.

According to the principal investigator Giora Pillar, M.D, Ph.D, with the Sleep Laboratory at Rambam Medical Center in Haifa, Israel, it is very difficult to objectively assess and quantify the capability of an individual to remain vigilant. Many of the study’s participants may have been highly motivated to overcome their sleepiness during the test in order to prevent their license from being revoked.

“It could be expected that the MWT40 will be superior to MWT20, but it is somewhat surprising that despite a strong drive to sleep, as in cases of severe apnea, people could pass the test by remaining awake in all trials,” said Pillar. “It emphasizes the strong effect of motivation.”

The study included 164 consecutive subjects with an average age of 50, who were referred to the Technion Sleep Lab between June 2006 and January 2007 by the Medical Institute for Driving Safety of the Ministry of Transportation. Participants who were suspected of suffering from EDS were referred for evaluation for their ability to maintain wakefulness for the purpose of renewal of their license to drive. Seventeen of the participants were professional drivers and one participant was an aviation pilot.

All subjects underwent a full-night polysomnograph followed by an MWT40, (four 40 minute long trials). During the MWT, participants were told to sit on a bed in a reclining position in a private, dimly lit room. Subjects were not allowed to perform any unusual action to maintain wakefulness, such as reading, talking, consuming caffeine or making repetitive movements. Trials were stopped if the subject fell asleep or if 40 minutes had passed.

According to Pillar, none of the participants who were receiving continuous positive airway pressure (CPAP) treatment failed the MWT 40; this information emphasizes the importance of treating OSA in preventing auto accidents caused by EDS. Pillar noted that findings of this study indicate that further research is necessary in order to determine a more efficient way to objectively assess an individual’s ability to remain vigilant while driving.

According to the American Academy of Sleep Medicine (AASM), OSA is a sleep-related breathing disorder that involves a decrease or complete halt in airflow despite an ongoing effort to breathe. It occurs when the muscles relax during sleep, causing soft tissue in the back of the throat to collapse and block the upper airway. This leads to partial reductions (hypopneas) and complete pauses (apneas) in breathing that can produce abrupt reductions in blood oxygen saturation. Brief arousals from sleep restore normal breathing but can cause a fragmented quality of sleep. Most people with sleep apnea snore loudly and frequently, and they often experience excessive daytime sleepiness.

AASM practice parameters for the MWT recommend the 40-minute protocol and advise that the MWT be used when sleep clinicians require objective data to assess an individual’s ability to remain awake. The MWT should be used in association with the clinical history to assess the ability to maintain wakefulness.

Experts say that poor air quality and ventilation is partly due to economies made by airlines to reduce fuel costs and extend the working life of aircraft.

In the study, a team of Belfast researchers measured oxygen saturation levels – the amount of oxygen carried in the blood.

Before take-off, levels averaged 97 per cent but these fell to 93 per cent at altitude.

For 54 per cent of travellers, the fall in oxygen levels was at least 6 per cent – a level at which many hospital doctors would prescribe extra oxygen.

The results were similar for both short-haul and long-haul fliers, according to the research published in Anaesthesia, the official journal of the Association of Anaesthetists of Great Britain and Ireland.

The 84 passengers who took part in the tests were aged between one and 78. None had severe cardio-respiratory problems and no one required permission from their doctor to fly.

Dr Susan Humphreys, anaesthetic specialist registrar, said research showed that a drop in oxygen levels in the blood can lead to an increase in blood clotting, which raises the risk of a deep vein thrombosis even in healthy people.

Illness Link

“We believe that these falling oxygen levels, together with factors such as dehydration, immobility and low humidity, could contribute to illness during and after flights,” she said.

“This has become a greater problem in recent years as modern aeroplanes are able to cruise at much higher altitudes.”

Dr Humphreys said oxygen deficiency can result in impaired mental performance and shortness of breath.

It can also worsen conditions such as angina and breathing problems.

Experts believe that a significant number of passengers travel with medical conditions that could put them at risk.

Farrol Kahn, of the Aviation Health Institute, a medical research charity promoting better health for passengers, said surveys show that around 10 per cent of travellers are unfit to fly.

“Oxygen reduction particularly affects people with pre-existing conditions, the old and very young, as infants can get into difficulty if they have insufficiently developed lungs,” he said.

“Economies play a role because if the altitude pressure is routinely changed on existing aircraft it cuts their working life.

“But passengers can ask for extra oxygen to be supplied to a section of the cabin and cylinders are available for giving individuals supplementary oxygen.”

Mr Kahn said travellers with cardiovascular disease or respiratory diseases such as bronchitis and asthma should have preflight checks, along with the over-50s, to ensure they were fit to fly.

“The conditions on board, especially long-haul flights, put special stress on essential organs such as heart and brain,” he added.

“At the Institute we provide medical advice to GPs who are concerned about whether a patient can fly after a stroke, for example.”

Mr Kahn said ventilation was cut on some flights to save fuel and, by making passengers sleepy, cut down on extra services needed on board.

A report on the risks of flying from the House of Lords select committee on science and technology said there should be display cards at every ticket sale point and in every doctor’s surgery asking intending passengers: “Are you fit to fly?