Validation of actigraphy sleep metrics in children aged 8 to 16 years: considerations for device type, placement and algorithms

BACKGROUND

Actigraphy is often used to measure sleep in pediatric populations, despite little confirmatory evidence of the accuracy of existing sleep/wake algorithms. The aim of this study was to determine the performance of 11 sleep algorithms in relation to overnight polysomnography in children and adolescents.

METHODS

One hundred thirty-seven participants aged 8-16 years wore two Actigraph wGT3X-BT (wrist, waist) and three Axivity AX3 (wrist, back, thigh) accelerometers over 24-h. Gold standard measures of sleep were obtained using polysomnography (PSG; Embletta MPRPG, ST + Proxy and TX Proxy) in the home environment, overnight. Epoch by epoch comparisons of the Sadeh (two algorithms), Cole-Kripke (three algorithms), Tudor-Locke (four algorithms), Count-Scaled (CS), and HDCZA algorithms were undertaken. Mean differences from PSG values were calculated for various sleep outcomes.

RESULTS

Overall, sensitivities were high (mean ± SD: 91.8%, ± 5.6%) and specificities moderate (63.8% ± 13.8%), with the HDCZA algorithm performing the best overall in terms of specificity (87.5% ± 1.3%) and accuracy (86.4% ± 0.9%). Sleep outcome measures were more accurately measured by devices worn at the wrist than the hip, thigh or lower back, with the exception of sleep efficiency where the reverse was true. The CS algorithm provided consistently accurate measures of sleep onset: the mean (95%CI) difference at the wrist with Axivity was 2 min (-6; -14,) and the offset was 10 min (5, -19). Several algorithms provided accurate measures of sleep quantity at the wrist, showing differences with PSG of just 1-18 min a night for sleep period time and 5-22 min for total sleep time. Accuracy was generally higher for sleep efficiency than for frequency of night wakings or wake after sleep onset. The CS algorithm was more accurate at assessing sleep period time, with narrower 95% limits of agreement compared to the HDCZA (CS:-165 to 172 min; HDCZA: -212 to 250 min).

CONCLUSION

Although the performance of existing count-based sleep algorithms varies markedly, wrist-worn devices provide more accurate measures of most sleep measures compared to other sites. Overall, the HDZCA algorithm showed the greatest accuracy, although the most appropriate algorithm depends on the sleep measure of focus.

Relationship of arsenic and chromium availability with carbon functional groups, aluminum and iron in Little Washita River Experimental Watershed Reservoirs, Oklahoma, USA

Sediment from three reservoirs located in the Little Washita River Experimental Watershed (LWREW) in Oklahoma, USA with contrasting dominant land uses were analyzed for total and extractable concentrations of arsenic (As) and chromium (Cr), and the potential ecologic risk to benthic organisms. Extractable As ranged from 0.24 to 1.21 mg kg^-1, in the order grazing>cropland>forest and 0.13-0.58 mg kg^-1 for extractable Cr, in the order of forest>grazing>cropland. However, only approximately < 1.5% of total As and < 4% of total Cr were extractable. Total As ranged from 16.2 to 141 mg kg^-1 and total Cr ranged from 5.06 to 40.1 mg kg^-1 both in the order of cropland>grazing>forest. The sediment exhibited an alkaline pH (8.0-8.7). As sorption exhibited a positive relationship with Al (r = 0.9995; P = 0.0001), Fe (r = 0.9829; P = 0.0001), and C (r = 0.4090; P = 0.0017) and Cr correlated positively with Al (r = 0.9676 P = 0.0001), Fe (r = 0.9818; P = 0.0001), and C (r = 0.3368; P = 0.0111). In addition, both As and Cr exhibited positive relationships with carbon (C) functional groups in the order of O-alkyl C> methoxyl C> alkyl C> aromatic C> carboxyl C> phenolic C. The sediment concentration analysis results illustrated that As in all reservoirs exceeded their respective Threshold Effect Level (TEL) and/or Probable Effect Level (PEL) indicating that existing concentrations of metals in these sediments were sufficiently high to cause adverse effects. However, Cr concentrations in all reservoirs evaluated was lower compared to the TEL and PEL.

A case-comparison study of pregnant women with mitochondrial disease - what to expect?

OBJECTIVE

Mitochondrial disease is a disorder of energy metabolism that affects 1 in 4300 adults in the UK. Pregnancy is associated with physiological demands that have implications for energy metabolism. We were interested to know how pregnancy was affected in women with mitochondrial disease, particularly those with the most common pathogenic mutation m.3243A>G.

DESIGN

Retrospective case-comparison study.

POPULATION/SETTING

Sixty-seven women with genetically confirmed mitochondrial disease from the UK Mitochondrial Diseases Cohort and 69 unaffected women participated.

METHODS

Participants answered questionnaires regarding each of their pregnancies. Patients were divided into two groups according to genetic mutation, with those harbouring m.3243A>G comprising a single group.

MAIN OUTCOME MEASURES

Pregnancy-related complications, mode of delivery, gestational age and birthweight of newborns.

RESULTS

Of 139 live births in the comparison group, 62 were in the m.3243A>G group and 87 were in the 'all other mutations' group. Pregnancies of women with the m.3243A>G mutation had significantly more gestational diabetes (odds ratio [OR] = 8.2, 95% CI 1.3-50.1), breathing difficulties (OR = 7.8, 95% CI 1.0-59.1) and hypertension (OR = 8.2, 95% CI 3.1-21.5) than the comparison group. Only half of the pregnancies in the m.3243A>G group had normal vaginal delivery, with emergency caesarean section accounting for 24.2% of deliveries. Babies were born significantly earlier to mothers harbouring m.3243A>G with 53.3% of them preterm (<37 weeks). These babies were also more likely to require resuscitation and admission.

CONCLUSION

Women who carried the m.3243A>G mutation appeared to be at higher risk of complications during pregnancies, caesarean section and preterm delivery than the unaffected women or those with other forms of mitochondrial disease.

TWEETABLE ABSTRACT

Pregnant women with mitochondrial disease - m.3243A>G mutation - are at greatly increased risk of complications and preterm delivery.

Correction: Mitochondrial oxodicarboxylate carrier deficiency is associated with mitochondrial DNA depletion and spinal muscular atrophy-like disease

This Article was originally published under Nature Research's License to Publish, but has now been made available under a [CC BY 4.0] license. The PDF and HTML versions of the Article have been modified accordingly.

Improving rates of overweight, obesity and extreme obesity in New Zealand 4-year-old children in 2010-2016

BACKGROUND

Prevalence of childhood obesity is high in developed countries, and there is a growing concern regarding increasing socio-economic disparities.

OBJECTIVES

To assess trends in the prevalence of overweight, obesity and extreme obesity among New Zealand 4-year olds, and whether these differ by socio-economic and ethnic groupings.

METHODS

A national screening programme, the B4 School Check, collected height and weight data for 75-92% of New Zealand 4-year-old children (n = 317 298) between July 2010 and June 2016. Children at, or above, the 85th, 95th and 99.7th percentile for age and sex adjusted body mass index (according to World Health Organization standards) were classified as overweight, obese and extremely obese, respectively. Prevalence rates across 6 years (2010/11 to 2015/16) were examined by sex, across quintiles of socio-economic deprivation, and by ethnicity.

RESULTS

The prevalence of overweight, obesity and extreme obesity decreased by 2.2 [95% CI, 1.8-2.5], 2.0 [1.8-2.2] and 0.6 [0.4-0.6] percentage points, respectively, between 2010/2011 and 2015/2016. The downward trends in overweight, obesity and extreme obesity in the population persisted after adjustment for sex, ethnicity, deprivation and urban/rural residence. Downward trends were also observed across sex, ethnicity and deprivation groups.

CONCLUSIONS

The prevalence of obesity appears to be declining in 4-year-old children in New Zealand across all socio-economic and ethnic groups.

Parental reactions to weight screening in young children: a randomized controlled trial

BACKGROUND

Parental inability to recognize child overweight and physician reluctance to instigate discussion prevents behaviour change.

OBJECTIVE

To evaluate parental acceptance of child overweight status following screening.

METHODS

Interviewers used motivational interviewing or best practice care to discuss overweight status of 271 young children (BMI ≥ 85^th ) with parents using simple traffic-light BMI charts. Follow-up sessions two weeks later (n = 251, 93%) were coded qualitatively to assess parental reactions to the information (overweight diagnosis) and how it was presented (feedback condition).

RESULTS

Eight-two percent of parents rated the charts positively with few (8-10%) feeling judged. Motivational interviewing parents viewed feedback as more empathetic (relative risk, 95% CI: 4.07, 1.64-10.09), but more uncomfortable (12.2, 1.48-100.1) than best practice care parents. Overall, 65.2% of parents accepted their child was overweight, 22.1% were ambivalent and 12.7% rejected the information. Although motivational interviewing parents were less likely to accept it (OR, 95% CI: 0.49, 0.37-0.64) and more likely to be ambivalent (2.01, 1.17-3.47), the most important predictor of acceptance was a positive experience of feedback (P < 0.001).

CONCLUSIONS

Simple traffic-light charts facilitate discussion of child overweight status with parents. Style of feedback is less relevant than ensuring a positive experience for parents to increase acceptance of the weight information.

Self-monitoring has no adverse effect on disordered eating in adults seeking treatment for obesity

OBJECTIVES

Although monitoring is considered a key component of effective behaviour change, the development of apps has allowed consumers to constantly evaluate their own diet, with little examination of what this might mean for eating behaviour. The aim of this study was to investigate whether self-monitoring of diet using the app MyFitnessPal or daily self-weighing increases the reported occurrence of eating disorders in adults with overweight/obesity following a weight loss programme.

METHODS

Two hundred fifty adults with body mass index ≥ 27 kg/m2 received diet and exercise advice and were randomized to one of four monitoring strategies (daily self-weighing, MyFitnessPal, brief monthly consults or self-monitoring hunger) or control for 12 months. The Eating Disorder Examination Questionnaire 6.0 was used to assess eating disorder symptoms and behaviours for the previous 28 d at 0 and 12 months.

RESULTS

There were no significant differences in the global Eating Disorder Examination Questionnaire score or the subscales between those in the four monitoring groups and the control at 12 months (all p ≥ 0.164), nor were there differences in binge eating, self-induced vomiting, laxative misuse or excessive exercise at 12 months (p ≥ 0.202). The overall prevalence of one or more episodes of binge eating was 53.6% at baseline and 50.6% at 12 months, with no change over time (p = 0.662).

CONCLUSIONS

There was no evidence that self-monitoring, including using diet apps like MyFitnessPal or daily self-weighing, increases the reported occurrence of eating disorder behaviours in adults with overweight/obesity who are trying to lose weight.

Effect of Perilesional Injection of α-interferon on Cervical Intraepithelial Neoplasia and Associated Human Papillomavirus Infection

In this controlled prospective study, 14 patients with cervical intraepithelial neoplasia (CIN) were observed for one month to exclude spontaneous regression, and then seven patients were treated twice-weekly with perilesional injections of alpha-interferon. Both groups were monitored colposcopically, and advised to use the contraceptive sheath. Cervical smears and biopsies for histology and viral studies were taken before and after the study. There was an improvement of six out of seven of the study group, with two complete cures. Koilocytosis disappeared if it had been present initially, as did human papillomavirus (HPV) 16. By contrast, three control cases showed improvement, but there were no cures, and one case deteriorated; Koilocytosis (2 cases) did not change; HPV 16 disappeared in two controls and appeared in one. A new focus of dysplasia appeared in a part of the transformation zone not being treated with alpha-interferon in one of the study cases, illustrating the advisability of treating the whole transformation zone in CIN.

Biallelic mutations in mitochondrial tryptophanyl-tRNA synthetase cause Levodopa-responsive infantile-onset Parkinsonism

Mitochondrial aminoacyl‐tRNA synthetases (mtARSs) are essential, ubiquitously expressed enzymes that covalently attach amino acids to their corresponding tRNA molecules during translation of mitochondrial genes. Deleterious variants in the mtARS genes cause a diverse array of phenotypes, many of which involve the nervous system. Moreover, distinct mutations in mtARSs often cause different clinical manifestations. Recently, the gene encoding mitochondrial tryptophanyl tRNA synthetase (WARS2) was reported to cause 2 different neurological phenotypes, a form of autosomal recessive intellectual disability and a syndrome of severe infantile‐onset leukoencephalopathy. Here, we report the case of a 17‐year‐old boy with compound heterozygous mutations in WARS2 (p.Trp13Gly, p.Ser228Trp) who presented with infantile‐onset, Levodopa‐responsive Parkinsonism at the age of 2 years. Analysis of patient‐derived dermal fibroblasts revealed decreased steady‐state WARS2 protein and normal OXPHOS content. Muscle mitochondrial studies suggested mitochondrial proliferation without obvious respiratory chain deficiencies at the age of 9 years. This case expands the phenotypic spectrum of WARS2 deficiency and emphasizes the importance of mitochondrial protein synthesis in the pathogenesis of Parkinsonism.

Potential phosphorus eutrophication mitigation strategy: Biochar carbon composition, thermal stability and pH influence phosphorus sorption

Phosphorus (P) eutrophication is a major pollution problem globally, with unprecedented amount of P emanating from agricultural sources. But little is known about the optimization of soil-biochar P sorption capacity. The study objective was to determine how biochar feedstocks and pyrolysis conditions influences carbon (C) thermal stability, C composition and pH and in turn influence the phosphorus sorption optimization. Biochar was produced from switchgrass, kudzu and Chinese tallow at 200, 300, 400, 500, 550, 650,750 °C. Carbon thermal stability was determined by multi-element scanning thermal analysis (MESTA), C composition was determined using solid state ¹³C NMR. Phosphorus sorption was determined using a mixture of 10% biochar and 90% sandy soil after incubation. Results indicate increased P sorption (P < 0.0001) and decreased P availability (P < 0.0001) with increasing biochar pyrolysis temperature. However, optimum P sorption was feedstock specific with switchgrass indicating P desorption between 200 and 550 °C. Phosphorus sorption was in the order of kudzu > switchgrass > Chinese tallow. Total C, C thermal stability, aromatic C and alkalinity increased with elevated pyrolysis temperature. Biochar alkalinity favored P sorption. There was a positive relationship between high thermal stable C and P sorption for Kudzu (r = 0.62; P = 0.0346) and Chinese tallow (r = 0.73; P = 0.0138). In conclusion, biochar has potential for P eutrophication mitigation, however, optimum biochar pyrolysis temperature for P sorption is feedstock specific and in some cases might be out of 300-500 °C temperature range commonly used for agronomic application. High thermal stable C dominated by aromatic C and alkaline pH seem to favor P sorption.

The effect of increasing risk and challenge in the school playground on physical activity and weight in children: a cluster randomised controlled trial (PLAY)

BACKGROUND

To investigate whether changing the play environment in primary schools to one that includes greater risk and challenge increases physical activity and reduces body mass index (BMI).

SUBJECTS/METHODS

A 2-year cluster randomised controlled trial was undertaken in 16 New Zealand schools (years 1-8). Intervention schools (n=8) redesigned their play environments to encourage imaginative and independent free play by increasing opportunities for risk and challenge (for example, rough-and-tumble play), reducing rules and adding new playground components (for example, loose parts). Control schools (n=8) were asked to not change their play environment. A qualified playworker rated all school play environments at baseline and 1 year. Primary outcomes were moderate-to-vigorous physical activity (7-day accelerometry) and BMI z-score, collected in 840 children at baseline, 1 and 2 years. Data were analysed using generalised estimating equations.

RESULTS

Multiple changes were made to the school play environments resulting in a significant difference in overall play evaluation score between intervention and control schools of 4.50 (95% confidence interval: 1.82 to 7.18, P=0.005), which represents a substantial improvement from baseline values of 19.0 (s.d. 3.2). Overall, schools liked the intervention and reported many benefits, including increased physical activity. However, these beliefs did not translate into significant differences in objectively measured physical activity, either as counts per minute (for example, 35 (-51 to 120) during lunch break) or as minutes of moderate-to-vigorous physical activity (0.4, -1.1 to 2.0). Similarly, no significant differences were observed for BMI, BMI z-score or waist circumference at 1 or 2 years (all P>0.321).

CONCLUSIONS

Altering the school play environment to one that promoted greater risk and challenge for children did not increase physical activity, nor subsequently alter body weight. Although schools embraced the concept of adding risk and challenge in the playground, our findings suggest that children may have been involved in different, rather than additional activities.

Bioelectrical impedance as a measure of change in body composition in young children

BACKGROUND AND OBJECTIVES

The ability of bioelectrical impedance (BIA) to measure change in body composition in children has rarely been examined.

METHODS

Body composition was estimated by BIA (Tanita BC-418) and dual-energy x-ray absorptiometry (DXA) in 187 children aged 4-8 years at baseline and at 12 months. Change in body composition was compared between the two methods using mixed models.

RESULTS

Estimates of change in fat mass did not differ between BIA and DXA for overweight girls (mean difference between methods, 95% confidence interval: 0.04 kg, -0.19 to 0.28) or boys (0.07 kg, -0.14 to 0.27). BIA was also able to accurately detect change in fat-free mass, with no significant differences between methods (-0.14 kg, -0.10 to 0.38 in girls and -0.07 kg, -0.35 to -0.20 in boys). Change in percentage fat produced similar estimates in both genders (0.18%, -0.82 to 0.46 in girls and 0.38%, -0.37 to 1.13 in boys). BIA/DXA comparisons in normal weight children were also not significantly different, with the exception of percentage fat in girls, where BIA slightly underestimated change compared with DXA (0.7%, 0.02-0.37).

CONCLUSION

BIA performed well as a measure of change in body composition, providing confidence for its use as an outcome measure in children.

Diquat causes caspase-independent cell death in SH-SY5Y cells by production of ROS independently of mitochondria

Evidence indicates that Parkinson's disease (PD), in addition to having a genetic aetiology, has an environmental component that contributes to disease onset and progression. The exact nature of any environmental agent contributing to PD is unknown in most cases. Given its similarity to paraquat, an agrochemical removed from registration in the EU for its suspected potential to cause PD, we have investigated the in vitro capacity of the related herbicide Diquat to cause PD-like cell death. Diquat showed greater toxicity towards SH-SY5Y neuroblastoma cells and human midbrain neural cells than paraquat and also MPTP, which was independent of dopamine transporter-mediated uptake. Diquat caused cell death independently of caspase activation, potentially via RIP1 kinase, with only a minor contribution from apoptosis, which was accompanied by enhanced reactive oxygen species production in the absence of major inhibition of complex I of the mitochondrial respiratory chain. No changes in α-synuclein expression were observed following 24-h or 4-week exposure. Diquat may, therefore, kill neural tissue by programmed necrosis rather than apoptosis, reflecting the pathological changes seen following high-level exposure, although its ability to promote PD is unclear.

A novel de novo STXBP1 mutation is associated with mitochondrial complex I deficiency and late-onset juvenile-onset parkinsonism

Mutations in STXBP1 have recently been identified as a cause of infantile epileptic encephalopathy. The underlying mechanism of the disorder remains unclear and, recently, several case reports have described broad and progressive neurological phenotypes in addition to early-onset epilepsy. Herein, we describe a patient with early-onset epilepsy who subsequently developed a progressive neurological phenotype including parkinsonism in her early teens. A de novo mutation in STXBP1 (c.416C>T, p.(Pro139Leu)) was detected with exome sequencing together with profound impairment of complex I of the mitochondrial respiratory chain on muscle biopsy. These findings implicate a secondary impairment of mitochondrial function in the progressive nature of the disease phenotype.

Novel internally branched, internal alkenes as major components of the cuticular hydrocarbons of the primitive australian antNothomyrmecia macrops Clark (Hymenoptera: Formicidae)

Internally mono- and dimethyl branched, internal alkenes, which constitute most of the cuticular hydrocarbon present on workers of the primitive Australian antNothomyrmecia macrops Clark, have been identified by gas chromatography-mass spectrometry. They are the first such alkenes reported from insects. Also present are alkanes with similar carbon skeletons. The hydrocarbon patterns of three separateNothomyrmecia colonies were very similar.

Mitochondrial DNA deletions and depletion within paraspinal muscles

Aims

Although mitochondrial abnormalities have been reported within paraspinal muscles in patients with axial weakness and neuromuscular disease as well as with ageing, the basis of respiratory deficiency in paraspinal muscles is not known. This study aimed to determine the extent and basis of respiratory deficiency in paraspinal muscles from cases undergoing surgery for degenerative spinal disease and post mortem cases without a history of spinal disease, where age-related histopathological changes were previously reported.

Methods

Cervical and lumbar paraspinal muscles were obtained peri-operatively from 13 patients and from six post mortem control cases (age range 18–82 years) without a neurological disease. Sequential COX/SDH (mitochondrial respiratory chain complex IV/complex II) histochemistry was performed to identify respiratory-deficient muscle fibres (lacking complex IV with intact complex II activity). Real-time polymerase chain reaction, long-range polymerase chain reaction and sequencing were used to identify and characterize mitochondrial DNA (mtDNA) deletions and determine mtDNA copy number status. Mitochondrial respiratory chain complex subunits were detected by immunohistochemistry.

Results

The density of respiratory-deficient fibres increased with age. On average, 3.96% of fibres in paraspinal muscles were respiratory-deficient (range 0–10.26). Respiratory deficiency in 36.8% of paraspinal muscle fibres was due to clonally expanded mtDNA deletions. MtDNA depletion accounted for further 13.5% of respiratory deficiency. The profile of immunohistochemically detected subunits of complexes was similar in respiratory-deficient fibres with and without mtDNA deletions or mtDNA depletion.

Conclusions

Paraspinal muscles appeared to be particularly susceptible to age-related mitochondrial respiratory chain defects. Clonally expanded mtDNA deletions and focal mtDNA depletion may contribute towards the development of age-related postural abnormalities.

Initial development and validation of a mitochondrial disease quality of life scale

Mitochondrial diseases are a clinically diverse group of genetic disorders that often present to neurologists. Health related quality of life (HRQOL) is increasingly recognised as a fundamental patient based outcome measure in both clinical intervention and research. Generic outcome measures have been extensively validated to assess HRQOL across populations and different disease states. However, due to their inclusive construct, it is acknowledged that not all relevant aspects of a specific illness may be captured. Hence there is a need to develop disease specific HRQOL measures that centre on symptoms characteristic of a specific disease or condition and their impact. This study presents the initial conceptualisation, development and preliminary psychometric assessment (validity and reliability) of a mitochondrial disease specific HRQOL measure (Newcastle Mitochondrial Quality of life measure (NMQ)). NMQ is a valuable assessment tool and consists of 63 items within 16 unidimensional domains, each demonstrating good internal reliability (Cronbach's α≥0.83) and construct validity.

Research priorities in 2012 for the effective management of childhood obesity

In 2010, the Management Stream of the Australasian Child and Adolescent Obesity Research Network (ACAORN) undertook a Delphi survey asking 'What research questions remain to be addressed in the effective management of child and adolescent obesity?' Members of ACAORN, the Child and Adolescent Obesity Clinics of Australasia Network (CAOCOA-Net) and attendees at the Child Obesity symposium at the annual scientific meeting for the Australian and New Zealand Obesity Society (ANZOS) contributed to three rounds of survey development. Although reasonable concordance in ratings was evident for all 10 questions, 'determining the best strategies for long-term weight management' and 'how best to support the primary healthcare system to achieve these strategies' were clearly identified as the highest research priorities. Other priorities included 'how best to identify the right children with whom to intervene' and 'managing factors which impact on service delivery'. Identifying priority research areas from those working in the field offers the opportunity to stimulate research collaboration and provide justification for funding applications.

Secular changes in BMI and the associations between risk factors and BMI in children born 29 years apart

What is already known about this subject Factors associated with children's body mass index (BMI) include parents' BMIs, birth weight, maternal smoking, sleep duration and television watching. Few studies have attempted to quantify either changes in the association between risk factors and BMI or the contribution of changes in the risk factors to increases in BMI over a generation. What this study adds The magnitude of the association between most risk factors and children's BMIs has not changed over a 29-year period. Increases in the population level of mothers' body mass index (BMI) explains ~20% of the increase in children's BMI whereas the smaller increase in fathers' BMI contributes only 6%. Maternal smoking, despite the decrease in prevalence, contributes ~17%.

OBJECTIVE

Using two cohorts born 29 years apart in Dunedin, New Zealand we aim to examine changes in risk factors and their associations with body mass index (BMI) at ages 3 and 7 years, and estimate their contribution to the secular changes in BMI at age 7 years.

METHODS

Birth weight and anthropometric measures at ages 3, 5 and 7 years were obtained for 974 participants in the Dunedin Multidisciplinary Health and Development Study (DMHDS), born in 1972-1973, and 241 in the Family Lifestyle, Activity, Movement and Eating Study (FLAME), born in 2001-2002. Information about maternal age, education and smoking in pregnancy, as well as breastfeeding, children's television time and time in bed, was obtained by questionnaire.

RESULTS

The increase in BMI over the 29-year period was 0.84 (95% CI 0.61, 1.06) kg m(-2) at age 7. A 1-unit difference in the mother's BMI was associated with a 0.06 (0.03, 0.08) kg m(-2) difference in offspring in both studies; the 3.4 (2.8, 4.0) kg m(-2) increase in the mothers' BMIs accounts for a change of 0.19 kg m(-2) in the children's BMI. The much smaller generational increase in fathers' BMI (0.7 kg m(-2) ) correspondingly had a more limited effect on change in child BMI over time (0.06 kg m(-2) ). Although smoking in pregnancy decreased by 15% (8, 21) its association with BMI increased from 0.20 (-0.01, 0.42) in the DMHDS cohort to 1.24 (0.76, 1.71) kg m(-2) in the FLAME cohort, contributing 0.18 kg m(-2) to the increase in children's BMI.

CONCLUSIONS

Societal factors such as higher maternal BMI and smoking in pregnancy contribute most to the secular increase in BMI, with changes in behavioural factors, including sleep and television viewing, having little effect in this setting.

A multi-center comparison of diagnostic methods for the biochemical evaluation of suspected mitochondrial disorders

A multicenter comparison of mitochondrial respiratory chain and complex V enzyme activity tests was performed. The average reproducibility of the enzyme assays is 16% in human muscle samples. In a blinded diagnostic accuracy test in patient fibroblasts and SURF1 knock-out mouse muscle, each lab made the correct diagnosis except for two complex I results. We recommend that enzyme activities be evaluated based on ratios, e.g. with complex IV or citrate synthase activity. In spite of large variations in observed enzyme activities, we show that inter-laboratory comparison of patient sample test results is possible by using normalization against a control sample.

Hypertrophic olivary degeneration on magnetic resonance imaging in mitochondrial syndromes associated with POLG and SURF1 mutations

Hypertrophic olivary degeneration (HOD) is associated with lesions within the dento-rubro-olivary pathway or Guillain-Mollaret triangle and may be associated clinically with palatal tremor. Here we report HOD on brain magnetic resonance (MR) imaging in three patients with progressive mitochondrial syndromes in the absence of palatal tremor. Two of the patients were found to have identical compound heterozygous mutations in the POLG gene, encoding the catalytic subunit of the mitochondrial DNA polymerase-γ, but presented with different clinical phenotypes. The first patient displayed the clinical syndrome of sensory ataxia, neuropathy, dysarthria, and ophthalmoparesis (SANDO), while the second patient was affected by a neurological disorder consisting of an ophthalmoplegia, myopathy, and neuropathy. The third case was a child with Leigh syndrome due to SURF1 gene mutations, who presented with a generalized tremor. We discuss the brain MR imaging findings in these three cases along with a literature review on the MR features of previously reported cases of patients with POLG gene mutations and Leigh disease due to SURF1 gene mutations. Our findings suggest that the presence of HOD, in the appropriate clinical setting, should alert the clinician to the possibility of a mitochondrial disorder and the need to screen for mutations in POLG and SURF1 genes.

Mitochondrial disease in pregnancy: a systematic review

Mitochondrial diseases are heterogeneous in clinical presentation and genotype. The incidence of known pathogenic mitochondrial DNA mutations in the general population is 1 in 500. Little is known about the implications of pregnancy for women with mitochondrial disease. We undertook a systematic review of the literature on mitochondrial disease in pregnancy. Ten case reports were identified. The most common complications were threatened preterm labour (5 women) and preeclampsia (4 women). Two women experienced magnesium sulphate toxicity. Pregnancy had a varied effect on mitochondrial disease with some women being asymptomatic; others developing mild symptoms such as exercise intolerance or muscle weakness which resolved postnatally; and others developed more serious, persistent symptoms such as symptomatic Wolff-Parkinson-White syndrome, persistent paraesthesia and focal segmental glomerulosclerosis. Women with mitochondrial disease appear to be at increased risk of complications during pregnancy and labour but further prospective cohort studies are needed.

The clinical, histochemical, and molecular spectrum of PEO1 (Twinkle)-linked adPEO

BACKGROUND

Mutations in the Twinkle (PEO1) gene are a recognized cause of autosomal dominant progressive external ophthalmoplegia (adPEO), resulting in the accumulation of multiple mitochondrial DNA (mtDNA) deletions and cytochrome c oxidase (COX)-deficient fibers in skeletal muscle secondary to a disorder of mtDNA maintenance. Patients typically present with isolated extraocular muscle involvement, with little apparent evidence of the clinical heterogeneity documented in other mtDNA maintenance disorders, in particular POLG-related disease.

METHODS

We reviewed the clinical, histochemical, and molecular genetics analysis of 33 unreported patients from 26 families together with all previous cases described in the literature to define the clinical phenotype associated with PEO1 mutations.

RESULTS

Ptosis and ophthalmoparesis were almost universal clinical features among this cohort, with 52% (17/33) reporting fatigue and 33% (11/33) having mild proximal myopathy. Features consistent with CNS involvement were rarely described; however, in 24% (8/33) of the patients, cardiac abnormalities were reported. Mitochondrial histochemical changes observed in muscle showed remarkable variability, as did the secondary mtDNA deletions, which in some patients were only detected by PCR-based assays and not Southern blotting. Moreover, we report 7 novel PEO1 variants.

CONCLUSIONS

Our data suggest a shared clinical phenotype with variable mild multiorgan involvement, and that the contribution of PEO1 mutations as a cause of adPEO may well be underestimated. Direct sequencing of the PEO1 gene should be considered in adPEO patients prior to muscle biopsy.

Multi-system neurological disease is common in patients with OPA1 mutations

Additional neurological features have recently been described in seven families transmitting pathogenic mutations in OPA1, the most common cause of autosomal dominant optic atrophy. However, the frequency of these syndromal 'dominant optic atrophy plus' variants and the extent of neurological involvement have not been established. In this large multi-centre study of 104 patients from 45 independent families, including 60 new cases, we show that extra-ocular neurological complications are common in OPA1 disease, and affect up to 20% of all mutational carriers. Bilateral sensorineural deafness beginning in late childhood and early adulthood was a prominent manifestation, followed by a combination of ataxia, myopathy, peripheral neuropathy and progressive external ophthalmoplegia from the third decade of life onwards. We also identified novel clinical presentations with spastic paraparesis mimicking hereditary spastic paraplegia, and a multiple sclerosis-like illness. In contrast to initial reports, multi-system neurological disease was associated with all mutational subtypes, although there was an increased risk with missense mutations [odds ratio = 3.06, 95% confidence interval = 1.44-6.49; P = 0.0027], and mutations located within the guanosine triphosphate-ase region (odds ratio = 2.29, 95% confidence interval = 1.08-4.82; P = 0.0271). Histochemical and molecular characterization of skeletal muscle biopsies revealed the presence of cytochrome c oxidase-deficient fibres and multiple mitochondrial DNA deletions in the majority of patients harbouring OPA1 mutations, even in those with isolated optic nerve involvement. However, the cytochrome c oxidase-deficient load was over four times higher in the dominant optic atrophy + group compared to the pure optic neuropathy group, implicating a causal role for these secondary mitochondrial DNA defects in disease pathophysiology. Individuals with dominant optic atrophy plus phenotypes also had significantly worse visual outcomes, and careful surveillance is therefore mandatory to optimize the detection and management of neurological disability in a group of patients who already have significant visual impairment.

Reversible valproate hepatotoxicity due to mutations in mitochondrial DNA polymerase γ (POLG1)

We report the case of a 2-year-old boy with seizures who developed hepatic failure shortly after commencing sodium valproate. Unexpectedly, liver function returned to normal on stopping the drug. Sequencing of the mitochondrial polymerase γ gene (POLG1) revealed four heterozygous substitutions, two of which have been identified in cases of Alpers-Huttenlocher disease.

Two cases with progressive cystic leukoencephalopathy

Leukoencephalopathies with cystic changes in the white matter on magnetic resonance imaging are aetiologically heterogeneous neurological disorders seen in children. A group of leukoencephalopathies characterised by white matter lesions progressing to multifocal cystic degeneration has been reported in various disorders, including mitochondrial enzyme deficiencies, leukodystrophies, and infectious processes. We report two patients with leukoencephalopathy showing progressive cystic changes on serial MRI, and magnetic resonance spectroscopy resembling progressive cavitating leukoencephalopathy.

A novel mitochondrial DNA mutation in COX1 leads to strokes, seizures, and lactic acidosis

Cytochrome c oxidase (COX) is the terminal enzyme of the respiratory chain, with subunits originating both from the mitochondrial and nuclear genome. An eleven-year-old female presented initially with a seizure followed two months later with tonic-clonic seizures, weakness and aphasia. MRI of the cerebral hemispheres showed multiple infarcts. Previous history suggested gross and fine motor control deficits with learning difficulties. A muscle biopsy showed a specific decrease of COX staining in all fibres and pleomorphic mitochondria. Respiratory chain studies confirmed an isolated complex IV defect in muscle, whilst fibroblasts showed an initial COX activity below normal which rapidly came up to the normal range on culture. Sequencing of mtDNA revealed an heteroplasmic m.7023G>A mutation in the COX1 gene, with levels of 96% in muscle, 70% in blood and 50% in the initial skin fibroblast culture dropping to 10% in later passages. The mutation was present in a critical region of the COX1 gene, the V374M change being close to the two histidine residues His376 and His378 co-ordinating with the heme a and a (3), and His367 which co-ordinates a magnesium ion. This case highlights that a MELAS-like syndrome can occur with isolated COX deficiency.