Journals watch: London cycle hire scheme | Screening for type 2 diabetes

Too busy to read all of the journals? Dr Jonathan Holliday selects papers of interest to GPs.

London's cycle hire scheme appears to benefit older age groups
London's cycle hire scheme appears to benefit older age groups

Is the London cycle hire scheme good for people's health?

BMJ 2014; 348: g425

This study used the total population operational registration and use for the London cycle hire scheme (collected in April 2011 to March 2012), surveys of cycle hire users (collected during 2011) and London data on travel, physical activity, road traffic collisions and particulate air pollution. Benefit (or otherwise) was measured in Disability Adjusted Life Years (DALYs).

Users made 7.4m cycle hire trips. Of these, 31% would otherwise have gone on foot and 47% would have used public transport. When cycle hire injury rates were modelled as equal to the background injury rates for all cycling in London, any benefit disappeared for women, but there was still a benefit of 49 DALYs for men. It is thought this difference represents the higher collision fatality rates for female cyclists.

For the older age group, the modelled benefits were much greater than the harms, but for the youngest (15-29 years), medium-term benefits and harms were both comparatively small and potentially negative.

The authors conclude the scheme has positive health impacts, but these are clearer for men than for women and for older users than for younger users. If the research period had included 2013, when so many cycling fatalities were reported, I wonder if the conclusions would hold true?

Screening for type 2 diabetes in adolescent patients

J Adolesc Health 2014; 54: 139-43

In this US study, the authors contacted 700 paediatricians and 700 family practitioners to see which tests, particularly HbA1c, doctors ordered in a hypothetical scenario of a potentially diabetic adolescent.

The scenario involved an obese 14-year-old female with at least two risk factors for type 2 diabetes (positive family history, race or signs of insulin resistance) presenting for a routine medical examination.

Some 58% of the doctors ordered an HbA1c, which included 38% of the total who ordered both a fasting glucose and an HbA1c.

In 2000 the American Diabetic Association recommended that children aged over 10 years with a BMI >85th percentile should have a fasting plasma glucose or two-hour glucose tolerance test. In 2010 this was modified to allow HbA1c testing to be used to diagnose diabetes (HbA1c >6.5%) and prediabetes (5.7-6.4%). This study concludes that the sensitivity of HbA1c was not as good and the cost was greater, so perhaps this is not a plan for the UK to follow.

Is mammography worthwhile?

BMJ 2014; 348: g366

This report from Canada compares breast cancer incidence and mortality in women who did or did not undergo mammography screening.

All 90,000 entrants in the study had a physical examination and were taught breast self-examination.

Most importantly, the study found no evidence of any reduction in breast cancer mortality from mammography screening in a programme offering five annual screens, in either women aged 40-49 at study entry or in women aged 50-59.

There was a difference in survival after diagnosis of breast cancer by mammography alone compared with those diagnosed by physical examination screening, but the authors felt this was due to lead time, length time bias and overdiagnosis.

Overall, 1,005 women died from breast cancer in the 25-year follow-up period. The 25-year survival was 77% for those with tumours less than 2cm in size and 55% for those greater than 2cm. For those detected in the mammography arm, it was 71%, compared with 63% in the control arm. The authors cite a 22% 'overdiagnosis rate' and suggest this is the first time it has been estimated.

Risk of self-harm and suicide

J R Soc Med 2014; doi:10.1177/0141076814522033

Self-harm is more common in mental illness, but there is an additional risk of self-harm and suicide associated with physical illnesses.

This retrospective study looked at patients admitted to NHS hospitals between 1999 and 2011 with specified conditions as compared to controls. Subsequent hospital episodes for self-harm or suicide were compared between the matched cohorts to obtain rate ratios (RRs).

The psychiatric illnesses all had RRs >5. But in the physical illnesses, epilepsy, for example, had an RR of 2.9, asthma 1.8, diabetes 1.6 and inflammatory polyarthropathies 1.4.

Also interesting were the low RRs: cancer 0.95, congenital heart disease 0.9 and ulcerative colitis 0.8.

Reflect on this article and add notes to your CPD Organiser on MIMS Learning

  • Dr Holliday is a GP in Berkshire and a member of our team who regularly review the journals

These further action points may allow you to earn more credits by increasing the time spent and the impact achieved.

  • Audit 14- to 16-year-olds in the practice to see how many have had their BMI recorded within the past year. Of those with a BMI over the 95th percentile, how many have been screened for diabetes?
  • Review the practice uptake of mammography screening and compare with the uptake figures for your local screening centre.
  • Introduce a trial period of case-finding among the practice's asthmatic patients, looking for depression or thoughts of deliberate self-harm. This could form part of the annual asthma review.

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