A new study has found that 4-year-olds with shorter than average sleep times have increased rates of "externalizing" behaviour problems.

"Preschool children with shorter night time sleep duration had higher odds of parent-reported overactivity, anger, aggression, impulsivity, tantrums, and annoying behaviours," according to the new research by Dr. Rebecca J. Scharf of University of Virginia, Charlottesville, and colleagues.

They recommend that parents and health care providers discuss steps to improve sleep habits for preschool-age children with behaviour problems.

The researchers analyzed parent responses from a nationally representative study of approximately 9,000 children, followed from birth through kindergarten age.

When the children were four years old, night time sleep duration was estimated by asking the parents what time their child typically went to bed and woke on weekdays.

On a standard child behaviour questionnaire, parents rated their child on six different "externalizing" behaviour problems such as anger and aggression. (Externalizing behaviour problems are outward behaviours, distinguished from "internalizing" problems such as depression and anxiety.)

The relationship between sleep duration and behaviour scores was assessed, with adjustment for other factors that might affect sleep or behaviour.

The average bedtime was 8:39 pm and wake time 7:13 am, giving a mean night time sleep duration of about 10 and a half hours. Eleven percent of children were considered to have "short sleep duration" of less than 9 hours 45 minutes (calculated as one standard deviation below the average).

On the child behaviour questionnaire, 16 percent of children had a high score for externalizing behaviour problems.

Behaviour problems were more common for boys, children who watched more than two hours of television daily, and those whose mothers reported feeling depressed.

After adjustment for other factors, "Children in the shortest sleep groups have significantly worse behaviour than children with longer sleep duration," Dr Scharf and colleagues write.

The effect was greatest for aggressive behaviour problems, which were about 80 percent more likely for children with night time sleep duration of less than 9 hours and 45 minutes.

The study is published in the Journal of Developmental and Behavioral Pediatrics, the official journal of the Society for Developmental and Behavioral Pediatrics.

Despite public health campaigns, smoking remains the leading avoidable cause of death worldwide, killing almost six million people a year, mostly in low- and middle-income countries, the World Health Organization has said.

If current trends hold, the number of deaths blamed on tobacco use will rise to eight million a year in 2030, the WHO said yesterday in a briefing unveiled at a conference in Panama.

About 80 percent of tobacco-related deaths forecast for 2030 are expected in low- and middle-income countries, the report added.

"If we do not close ranks and ban tobacco advertising, promotion and sponsorship, adolescents and young adults will continue to be lured into tobacco consumption by an ever-more aggressive tobacco industry," said WHO Director-General Dr Margaret Chan.

"Every country has the responsibility to protect its population from tobacco-related illness, disability and death."

Among the dead this year, five million were tobacco users or former users, while more than 600,000 died from second-hand smoke, according to the WHO.

Tobacco use is believed to have caused the deaths of 100 million people in the 20th century.

Barring dramatic change, the tally for this century could soar to one billion people, the WHO warned.

"We know that only complete bans on tobacco advertising, promotion and sponsorship are effective," Dr Douglas Bettcher, the Director of the WHO`s Prevention of Noncommunicable Diseases department, told the Panama conference.

"Countries that introduced complete bans together with other tobacco control measures have been able to cut tobacco use significantly within only a few years," he said.

The report noted that 2.3 billion people from 92 countries benefit from some form of smoking restrictions, more than double the number who did five years ago.

However, that figure still represents just a third of the world`s population, it said.

Women working in irregular shifts are likely to experience reduced fertility and greater menstrual disruption than those working in regular shifts, according to a new research.

The team of researchers led by Dr Linden Stocker and Dr Ying Cheong, Southampton's Princess Anne Hospital, assessed the impact of non-standard working schedules, which included night and mixed shifts, on the reproductive outcomes of 119,345 women.

The study found that women who worked only nights had 29 percent increased rate of miscarriage.

Women who worked in rotational shifts had an 80 percent higher rate of subfertility - meaning that they were unable to conceive within a year compared with those working regular hours.

Women working out of the typical 9 am to 6 pm schedule also had a 33% higher rate of menstrual disruption, the study found.

"We don't fully understand why shift workers have an increased risk of certain diseases but obviously shift work impacts on your biological functioning, your psychological functioning and your social functioning", Dr Stocker was quoted as saying by an English news website.

The researchers, however, have asked women not to jump to a conclusion and quit jobs as the study is still in the preliminary stage.

Working odd hours is often linked to sleep loss, decreased exercise and poorer diet thereby drastically disrupting a woman's body clock.

In a previous study, researchers had claimed that women who had worked in nights shifts for 30 or more years are twice as likely to suffer from breast cancer.

Irregular bedtimes in early childhood have been linked with low scores in reading, maths in both boys and girls, a study has suggested.

The study authors looked at whether bedtimes in early childhood were related to brain power in more than 11,000 seven year olds, all of whom were part of the UK Millennium Cohort Study (MCS).

The research drew on regular surveys and home visits made when the kids were 3, 5, and 7, to find out about family routines, including bedtimes.

The authors wanted to know whether the time a child went to bed, and the consistency of bed-times, had any impact on intellectual performance, measured by validated test scores for reading, maths, and spatial awareness.

And they wanted to know if the effects were cumulative and/or whether any particular periods during early childhood were more critical than others.

Irregular bedtimes were most common at the age of 3, when around one in five children went to bed at varying times. By the age of 7, more than half the children went to bed regularly between 7.30 and 8.30 pm.

Children whose bedtimes were irregular or who went to bed after 9 pm came from more socially disadvantaged backgrounds, the findings showed.

When they were 7, girls who had irregular bedtimes had lower scores on all three aspects of intellect assessed, after taking account of other potentially influential factors, than children with regular bedtimes. But this was not the case in 7 year old boys.

Irregular bedtimes by the age of 5 were not associated with poorer brain power in girls or boys at the age of 7. But irregular bedtimes at 3 years of age were associated with lower scores in spatial awareness in both boys and girls, suggesting that around the age of 3 could be a sensitive period for cognitive development.

Girls who had never had regular bedtimes at ages 3, 5, and 7 had significantly lower reading, maths and spatial awareness scores than girls who had had consistent bedtimes. The impact was the same in boys, but for any two of the three time points.

The authors point out that irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation, so undermining the plasticity of the brain and the ability to acquire and retain information.

They wrote that sleep is the price that people pay for plasticity on the prior day and the investment needed to allow learning fresh the next day.

They added that early child development has profound influences on health and wellbeing across the life course, therefore, reduced or disrupted sleep, especially if it occurs at key times in development, can have important impacts on health throughout life."

Researchers including an Indian origin have shed some light on why aspirin benefits some people and not others.

Researchers at Duke Medicine developed a blood-based test of gene activity that has been shown to accurately identify who will respond to the therapy.

The study showed that the new gene expression profile not only measures the effectiveness of aspirin, but also serves as a strong predictor of patients who are at risk for heart attack.

The Duke researchers enlisted three groups of participants - two of healthy volunteers and one comprised of patients with heart disease seen in outpatient cardiology practices.

The healthy volunteers were given a dosage of 325 mg of aspirin daily for up to a month; the heart disease patients had been prescribed a low dose of aspirin as part of their treatment.

Blood was then analyzed for the impact of aspirin on RNA expression and the function of platelets, which are the blood cells involved in clotting.

The RNA microarray profiling after aspirin administration revealed a set of 60 co-expressed genes that the researchers call the "aspirin response signature," which consistently correlated with an insufficient platelet response to aspirin therapy among the healthy subjects as well as the heart disease patients.

The researchers also examined the aspirin response signature in another group of patients who had undergone cardiac catheterizations. They found the signature was also effective in identifying those patients who eventually suffered a heart attack or died.

Deepak Voora, M.D., assistant professor of medicine at Duke and lead author of the study, said that the aspirin response signature can determine who is at risk for heart attack and death.

He said that there is something about the biology of platelets that determines how well we respond to aspirin and we can now capture that with a genomic signature in blood.

The study has been published in the online edition of the Journal of the American College of Cardiology.