Ann Robinson’s research reviews—10 September 2021

Mobile stroke units—less disability at 90 days

Mobile stroke units (MSUs) are ambulances that carry specially trained staff, a CT scanner, and tissue plasminogen activator (t-PA). This observational, prospective trial looked at outcomes from MSUs compared with standard emergency medical services (EMS), which take people with a suspected acute ischaemic stroke into hospital as quickly as possible but don’t administer t-PA on the spot. The MSU group generally fared better than the EMS group. The median time from the onset of stroke symptoms to t-PA was 72 minutes in the MSU group versus 108 minutes for the EMS group. The percentage of eligible patients who received t-PA was 97.1% versus 79.5% (MSU v EMS), the mean score on utility-weighted modified Rankin score (an updated clinician-reported measure of global disability after stroke) was 0.72 versus 0.66, and mortality at 90 days was 8.9% versus 11.9%. Timing is key in stroke outcomes, and in this study a total of 32.9% of those in the MSU group were treated in the first “golden” hour compared with only 2.6% of those in the EMS group. The trial wasn’t randomised because it wouldn’t have been ethical to withhold MSU where it was available, and this may have introduced bias in group assignment. There were 10 times as many stroke alerts as confirmed cases of strokes that were eligible for t-PA; any measures that safely reduce that ratio will make the MSU service more cost effective.

N Engl J Med doi:10.1056/NEJMoa2103879

No link between subclinical thyroid dysfunction and dementia

Are thyroid function tests useful in the prevention or treatment of dementia? Most of us probably throw in the blood test as part of an assessment of anyone with cognitive decline. But this very useful, large (114 267 person-years), multicohort, individual participant data analysis found that there was no association between subclinical thyroid dysfunction and cognitive function, annual cognitive decline, or the onset of diagnosed dementia. There’s no way of knowing if the same was true for overt (symptomatic) hyperthyroidism or hypothyroidism. There may have been confounders due to missing data such as educational attainment, and for most cohorts only a baseline thyroid function test was available so the impact of any changes in thyroid status couldn’t be captured. The incidence of dementia was low so a link between thyroid dysfunction and the risk of dementia can’t be totally ruled out.  But the study’s authors comment that treating subclinical hypothyroidism is not without risks; overtreatment may trigger atrial fibrillation and strokes. There seems little justification for running that risk.

JAMA Intern Med doi:10.1001/jamainternmed.2021.5078

Lonely older people fare badly in intensive care

This US observational cohort study of nearly 1000 older people (median age 81 years) with critical illness found that each 1 point increase in the social isolation score before admission to intensive care (ICU) was associated with a 7% greater disability count and a 14% increase in 1 year mortality risk. An estimated one in five older adults in the US lacks close meaningful social ties with family or friends, and this study adds to known associations between isolation and poor health outcomes, even after accounting for illness severity and poverty. The question remains; if an individual in ICU is known to be socially isolated, what can be done? Options include support groups for ICU survivors, buddy programmes, follow-up weekly phone calls, and transport to attend outpatient appointments. Further research is needed to assess whether measures to reduce social isolation improve outcomes, but it’s hard to see a downside.

JAMA Intern Med doi:10.1001/jamainternmed.2021.5022

Air purification to reduce asthma symptoms: a lot of hot air?

Would it help children with asthma if their classrooms had cleaner air? This small factorial randomised trial in 41 US elementary schools found that a school-wide integrated pest management (IPM) programme to reduce mouse allergens or use of high efficiency particulate air (HEPA) filter purifiers to reduce particles and common airborne allergens had no significant effect on children with known asthma in a two week period compared with sham interventions. There were technical limitations in assessing the impact of the measures, but the results suggest that reducing particle and allergen exposure in school to the extent that was achieved didn’t improve the health of asthmatic children.

JAMA doi:10.1001/jama.2021.11559

Nipping familial hypercholesterolaemia in the bud

This cross sectional assessment of adults with likely heterozygous familial hypercholesterolaemia (FH) whose details had been entered into global registries across 56 countries found that FH tends to be diagnosed late (median age 44 years) and inadequately treated. Levels of LDL cholesterol recommended in guidelines were rarely achieved (median LDL 5.43 mmol/L in untreated patients and 4.23 mmol/L in those taking lipid lowering drugs). Only a tiny minority (2.7% of those on medication) had an LDL <1.8 mmol/L, and many of those were taking three drugs. Unsurprisingly, the prevalence of coronary disease rose in tandem with rising untreated LDL levels. Rates of coronary disease among women were half that of men, but underdiagnosis may account for some of that difference. Earlier diagnosis and more effective treatment of FH, using combination therapies if necessary, are advised.

Lancet doi:10.1016/S0140-6736(21)01122-3

Ann Robinson is an NHS GP and health writer and broadcaster