Journals watch: Cardiac function, vitamin D in type 2 diabetes and reducing readmission rates

Exercise and cardiac function

Circulation 2014 doi: 10.1161/CIRCULATIONAHA.114.010775

Endurance athletes have different cardiac morphological manifestations from those of more sedentary people, and it has been suggested that this is because the athletes' genes are different.

In an attempt to determine if this hypothesis is correct, this study assessed 12 previously sedentary people in their twenties and thirties (male and female), who were trained progressively and intensively for 12 months, so they could compete in a marathon by the end of that year.

MRIs for assessment of right and left ventricular mass and volumes were obtained at baseline and after three, six, nine and 12 months of training. Maximum oxygen uptake and cardiac output at rest and during exercise were measured. Pulmonary artery catheterisation was also performed at the start of the study and after one year.

The results showed that their oxygen uptake increased, as did their maximal cardiac output and stroke volume. Left and right ventricular mass increased progressively with training duration and intensity, and reached levels similar to those observed in elite endurance athletes.

However, there were some differences compared to elite athletes - the study participants' cardiac compliance and performance were lower.

Body fat and cardiovascular risk

Heart 2014; 100: 1613-19

It is often confusing when talking to patients about cardiovascular risk factors. Which is the most significant, BMI, WHR, or body fat?

This prospective cohort study was undertaken to determine if body fat percentage can predict mortality and cardiovascular disease (CVD) when other obesity indices are considered. It involved following up more than 15,000 patients who attended a health examination in 1997-2000, for all-cause mortality and incidence of CVD.

After exclusion of prior stroke, MI and cancer, and adjusting for potential confounders, BMI and WHR, the hazard ratios of mortality for men were 0.86, 0.81 and 0.76, and for women, 0.91, 0.75 and 0.87 for second, third and fourth quartile compared with the first (bottom) quartile of body fat percentage.

Higher BMI and WHR were associated with an increased risk of both outcomes and WHR appeared to have the best predictive value of the three indices. The authors conclude that once BMI and WHR are taken into account, fat percentage does not add to prediction of mortality or CVD in middle-aged and older adults.

Vitamin D and type 2 diabetes

Lancet Diabetes Endocrinol 2014 doi:10.1016/S2213-8587(14)70184-6

Low circulating 25-hydroxyvitamin D (25(OH)D) is associated with an increased risk of type 2 diabetes. However, it is unknown whether this is simply an association.

This study used several data sources from populations of European descent, including type 2 diabetes cases and non-cases, to perform a Mendelian randomisation analysis using single nucleotide polymorphisms (SNPs) within or near four genes related to 25(OH)D synthesis and metabolism.

Each SNP was assessed for an association with circulating 25(OH)D concentration, risk of type 2 diabetes and glycaemic traits.

The results indicated that the association between 25(OH)D concentration and type 2 diabetes is unlikely to be causal. This means vitamin D supplementation may not reduce the risk of type 2 diabetes.

Reducing readmission rates

Ann Intern Med 2014; 161(7): 472-81

This US study examined whether a peri-discharge, nurse-led intervention decreased emergency department visits or readmissions in ethnically and linguistically diverse older (>55) patients admitted to hospital.

In this randomised, controlled study, usual care was compared with in-hospital, one-on-one, self-management education given by a dedicated language-concordant registered nurse, combined with telephone follow-up by a nurse practitioner after discharge.

I presumed this level of intervention would surely result in lower readmission rates, but it did not.

Bariatric surgery for severely obese adolescents

Arch Dis Child 2014; 99: 894-8

NICE guidelines state that bariatric surgery can be considered for severely obese young people in 'exceptional circumstances'.

This study reported on six children aged 14-16 years who underwent surgery. Their mean BMI was 62.7. Unsurprisingly, many of these children also had hypertension, insulin resistance, obstructive sleep apnoea, limited mobility, benign intracranial hypertension and psychosocial problems.

Their mean percentage of weight loss, as a percentage of total body weight at six and 12 months, was 22% and 27%, respectively.

In addition to weight loss, other benefits included resolution of hypertension, improved school attendance and no progression to type 2 diabetes.

This confirms that bariatric surgery in these types of children can be extremely beneficial.

Obesity and response to the influenza vaccine

J Infect Dis 2014; 210: 1270-4

This study offers an interesting perspective on the influenza vaccine. It examined the immune response to H1N1 vaccine (2009) among children and adults with differing BMI. Obesity is recognised to be a risk factor for morbidity and mortality associated with influenza.  

In the study, serological response to the vaccine was measured. Although a single vaccine produced higher haemagglutination inhibition antibody titres at day 21 in obese compared with non-obese adults, there were no significant differences in responses to H1N1 vaccine among children or adults of differing BMI following two doses.

It would be interesting to know if there is any difference in serological response after the current single-dose vaccine in those children who are obese compared with those who have a normal BMI.

Rates of prescribing for patients with ADHD

Br J Pharmacol 2014; 205: 291-7

The incidence and prevalence of ADHD continue to rise and many patients are now receiving medication for this condition. Some experts feel too many patients are given medication too early.

These drugs are not without risks and side-effects. 

This study was carried out to assess the baseline and longitudinal influences of behavioural and environmental factors on ADHD medication use.  

The results showed there was a wide range in the number of children with ADHD given medication, ranging from 0.2% to 8.6%.  

Among all of the social variables examined, low maternal education increased the likelihood of medication use, whereas immigrant status lowered this likelihood. The likelihood of receiving ADHD medication was not predicted by psychiatric comorbidity or by parenting. We need to be aware of this variation in prescribing.

• Dr Newson is a GP in the West Midlands and a member of our team who regularly review the journals

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