Research news: March 2013
No evidence of cancer risk from folate supplements
Lancet 2013; doi:10.1016/S0140-6736(12)62001-7
Concerns about links between folate supplements and some types of cancer led researchers to reanalyse the individual datasets of 13 placebo controlled trials. The pooled results were reassuring. Participants taking folate supplements were no more likely than controls to develop new cancers during an average follow-up of five years (1904 cancers in the folic acid groups v 1809 cancers in the placebo groups; relative risk 1.06, 95% CI 0.99 to 1.13). They took between 0.5 mg and 5 mg a day, alone or in combination with B vitamins. The authors found no excess of any cancer type associated with folate supplements, and no link between cancer risk and duration of supplementation. 1
The authors hope their new analyses will help inform a longstanding debate about fortifying flour with extra folate to help prevent neural tube defects. Flour is already fortified in 50 countries including the US, Canada, and Australia. European governments have been more cautious, partly because a small transient spike in colorectal cancers occurred during the roll-out period in the US and Canada. These authors think it unlikely that fortification was responsible. The typical daily doses of folate from fortified flour are an order of magnitude smaller than the doses tested in trials of supplements. Three of the trials in their meta-analysis recruited adults with a previous colorectal adenoma.
Biologically, extra folate could reduce the risk of new cancers while encouraging growth of preclinical ones, says a linked editorial (doi:10.1016/S0140-6736(13)60110-5). This complex with cancer can be hard to see, even in large datasets. We should interpret with caution for now. (From BMJ 2013;346:f546)
Fit middle aged adults have a lower risk of dementia
Ann Intern Med 2013;158:162-8
A new study from the US has confirmed that the fitter you are in mid-life, the less likely you are to develop dementia later. The authors studied a cohort of nearly 20 000 healthy, well educated, and affluent adults from Texas who had a fitness test at a mean age of about 50 years. They looked for records of new dementia from any cause in claims from Medicare 20-30 years later. Medicare is federally funded health insurance for US adults aged 65 years or more. Participants in the top fifth of the distribution for fitness in mid-life were 36% less likely to make a new claim for dementia than adults in the bottom fifth, and the link was independent of hypertension, diabetes, smoking, body mass index, and serum lipids (hazard ratio 0.64, 95% CI 0.54 to 0.77).
This big study provides more good news about exercise and fitness in mid-life, says a linked editorial (p 213). It found an association between fitness and a lower risk of dementia even among healthy well remunerated men and women who attended a clinic for preventive health checks. Those in the bottom fifth looked fit by the standards of most previous studies. They must have been doing substantial amounts of exercise.
Simply telling people to do more exercise rarely works, says the editorial. A chance to reduce the risk of dementia might be a powerful motivator. (From BMJ 2013;346:f710)
Patients with coughs don’t need antibiotics—pass it on
JAMA Intern Med 2013; doi:10.1001/jamainternmed.2013.1589
When US researchers tested a complex intervention to discourage inappropriate antibiotic prescribing for uncomplicated bronchitis, they were rewarded with a significant drop in primary care prescriptions over one winter season. Printed leaflets, posters, and algorithms seemed to work, as well as similar materials incorporated into computerised decision support. Prescriptions for antibiotics fell from 80% to 67% among patients with bronchitis in the print strategy group and from 74% to 61% in the computerised strategy group. Prescriptions went up slightly in control practices.
Could this be another effective way to change doctors’ behaviour? Not really, says a linked editorial (doi:10.1001/jamainternmed.2013.1984). Healthy people with uncomplicated bronchitis should never be given antibiotics. We have known this for 40 years and should be aiming for prescribing rates below 10%.
Efforts to change have been well made and well evaluated. We know what works, but nothing seems to work well enough. Traditional medical interventions have failed, and it may be time to look further afield to business leaders, behavioural economists, and psychologists for inspiration. We might also be clearer with patients about just what they can expect from antibiotics—a few will recover slightly faster, between 5% and 25% will have an adverse reaction, and at least one in every 1000 will present to an emergency department with a serious drug related event.(From BMJ 2013;346:f254)
“Women who smoke like men, die like men”
N Engl J Med 2013;368:341-50
N Engl J Med 2013;368:351-64
Smoking has become substantially riskier for women during the past 50 years, say researchers. Analyses from two historical and five contemporary US cohorts suggest that the risks for women are now about the same as they are for men. Smokers of both sexes are now about 25 times more likely than never smokers to die of lung cancer, between 22 and 25 times more likely to die of chronic obstructive pulmonary disease (COPD), and nearly three times more likely to die of ischaemic heart disease.
Converging male and female risks may reflect changing smoking patterns in women, who now smoke like men (start earlier, smoke more), say the researchers. They also report an unexpected increase in deaths from COPD in male smokers and speculate that modern cigarettes that encourage deeper inhalation might be to blame.
A second cohort study linked smoking histories of around 202 000 US adults with mortality during seven years of follow-up to 2006. All cause mortality was three times higher for smokers than for similar adults who had never smoked (hazard ratio for women 3.0, 99% CI 2.7 to 3.3; hazard ratio for men 2.8, 2.4 to 3.1). The authors estimate that smokers lose a whole decade of life expectancy and halve their chances of surviving from 25 to 79 years (38% v 70% for women and 26% v 61% for men).
In further analyses, smokers who stopped before the age of 34 years regained the whole 10 years. Those who stopped at 35-44 years of age gained nine years of life expectancy, and those who stopped at 45-54 years and 55-64 years gained six years and four years, respectively.(From BMJ 2013;346:f543)
Cite this as: Student BMJ 2013;21:f887