Selected and shared hematological responses to apnea in elite human free divers and northern elephant seals (Mirounga angustirostris).

Despite elite human free divers achieving incredible feats in competitive free diving, there has yet to be a study that compares consummate divers, (i.e. northern elephant seals) to highly conditioned free divers (i.e., elite competitive free-diving humans). Herein, we compare these two diving models and suggest that hematological traits detected in seals reflect species-specific specializations, while hematological traits shared between the two species are fundamental mammalian characteristics. Arterial blood samples were analyzed in elite human free divers (n = 14) during a single, maximal volitional apnea and in juvenile northern elephant seals (n = 3) during rest-associated apnea. Humans and elephant seals had comparable apnea durations (∼6.5 min) and end-apneic arterial Po2 [humans: 40.4 ± 3.0 mmHg (means ± SE); seals: 27.1 ± 5.9 mmHg; P = 0.2]. Despite similar increases in arterial Pco2 (humans: 33 ± 5%; seals: 16.3 ± 5%; P = 0.2), only humans experienced reductions in pH from baseline (humans: 7.45 ± 0.01; seals: 7.39 ± 0.02) to end apnea (humans: 7.37 ± 0.01; seals: 7.38 ± 0.02; P < 0.0001). Hemoglobin P50 was greater in humans compared to elephant seals (29.9 ± 1.5 and 28.7 ± 0.6 mmHg, respectively; P = 0.046). Elephant seals overall had higher carboxyhemoglobin (COHb) levels (5.9 ± 2.6%) compared to humans (0.8 ± 1.2%; P < 0.0001); however, following apnea, COHb was reduced in seals (baseline: 6.1 ± 0.3%; end apnea: 5.6 ± 0.3%) and was slightly elevated in humans (baseline: 0.7 ± 0.1%; end apnea: 0.9 ± 0.1%; P < 0.0002, both comparisons). Our data indicate that during static apnea, seals have reduced hemoglobin P50, greater pH buffering, and increased COHb levels. The differences in hemoglobin P50 are likely due to the differences in the physiological environment between the two species during apnea, whereas enhanced pH buffering and higher COHb may represent traits selected for in elephant seals.NEW & NOTEWORTHY This study uses similar methods and protocols in elite human free divers and northern elephant seals. Using highly conditioned divers (elite free-diving humans) and highly adapted divers (northern elephant seals), we explored which hematological traits are fundamentally mammalian and which may have been selected for. We found differences in P50, which may be due to different physiological environments between species, while elevated pH buffering and carbon monoxide levels might have been selected for in seals.

Shining new light on mammalian diving physiology using wearable near-infrared spectroscopy.

Investigation of marine mammal dive-by-dive blood distribution and oxygenation has been limited by a lack of noninvasive technology for use in freely diving animals. Here, we developed a noninvasive near-infrared spectroscopy (NIRS) device to measure relative changes in blood volume and haemoglobin oxygenation continuously in the blubber and brain of voluntarily diving harbour seals. Our results show that seals routinely exhibit preparatory peripheral vasoconstriction accompanied by increased cerebral blood volume approximately 15 s before submersion. These anticipatory adjustments confirm that blood redistribution in seals is under some degree of cognitive control that precedes the mammalian dive response. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to ambient air. We suggest that this frequent and reproducible reoxygenation pattern, without access to ambient air, is underpinned by previously unrecognised changes in cerebral drainage. The ability to track blood volume and oxygenation in different tissues using NIRS will facilitate a more accurate understanding of physiological plasticity in diving animals in an increasingly disturbed and exploited environment.

Assessment of the effect of the COVID-19 lockdown on glycaemic control in people with type 1 diabetes using flash glucose monitoring.

AIM: To describe the effect of the stringent lockdown measures, introduced in the UK on 23 March 2020 to curtail the transmission of COVID-19, on glycaemic control in people with type 1 diabetes using flash glucose monitoring. METHODS: We undertook an observational study of 572 individuals with type 1 diabetes for whom paired flash glucose monitoring data were available between early March and May 2020. The primary outcome was change in flash glucose monitoring variables. We also assessed clinical variables associated with change in glycaemic control. RESULTS: Percentage of time in range increased between March and May 2020 [median (interquartile range) 53 (41-64)% vs 56 (45-68)%; P < 0.001], with associated improvements in standard deviation of glucose (P <0.001) and estimated HbA1c (P <0.001). There was a small reduction in the number of individuals meeting the hypoglycaemia target of <5% per day (64% vs 58%; P = 0.004). Comparing changes in flash glucose monitoring data from March to May in 2019 with the same period in 2020 confirmed that these differences were confined to 2020. Socio-economic deprivation was an independent predictor of a ≥5% reduction in time in range during lockdown (odds ratio 0.45 for people in the two most affluent Scottish Index of Multiple Deprivation quintiles; P <0.001). CONCLUSIONS: Lockdown was not associated with a significant deterioration in glycaemic control in people with type 1 diabetes using flash glucose monitoring. However, socio-economic deprivation appeared to increase the risk of decline in glycaemic control, which has implications for how support is focused in challenging times.

Socio-economic differences in cardiovascular disease risk factor prevalence in people with type 2 diabetes in Scotland: a cross-sectional study.

AIM: To describe the association between socio-economic status and prevalence of key cardiovascular risk factors in people with type 2 diabetes in Scotland. METHODS: A cross-sectional study of 264 011 people with type 2 diabetes in Scotland in 2016 identified from the population-based diabetes register. Socio-economic status was defined using quintiles of the area-based Scottish Index of Multiple Deprivation (SIMD) with quintile (Q)1 and Q5 used to identify the most- and least-deprived fifths of the population, respectively. Logistic regression models adjusted for age, sex, health board, history of cardiovascular disease and duration of diabetes were used to estimate odds ratios (ORs) for Q1 compared with Q5 for each risk factor. RESULTS: The mean (sd) age of the study population was 66.7 (12.8) years, 56% were men, 24% were in Q1 and 15% were in Q5. Crude prevalence in Q1/Q5 was 24%/8.8% for smoking, 62%/49% for BMI ≥ 30 kg/m2 , 44%/40% for HbA1c ≥ 58 mmol/mol (7.5%), 31%/31% for systolic blood pressure (SBP) ≥ 140 mmHg, and 24%/25% for total cholesterol ≥ 5 mmol/l, respectively. ORs [95% confidence intervals (CI)] were 3.08 (2.95-3.21) for current smoking, 1.48 (1.44-1.52) for BMI ≥ 30 kg/m2 , 1.11 (1.08-1.15) for HbA1c ≥ 58 mmol/mol (7.5%), 1.03 (1.00-1.06) for SBP ≥ 140 mmHg and 0.87 (0.84-0.90) for total cholesterol ≥ 5 mmol/l. CONCLUSIONS: Socio-economic deprivation is associated with higher prevalence of smoking, BMI ≥ 30 kg/m2 and HbA1c ≥ 58 mmol/mol (7.5%), and lower prevalence of total cholesterol ≥ 5 mmol/l among people with type 2 diabetes in Scotland. Effective approaches to reducing inequalities are required as well as reducing risk factor prevalence across the whole population.

Socio-economic status and mortality in people with type 1 diabetes in Scotland 2006-2015: a retrospective cohort study.

AIMS: To describe the association between socio-economic status and mortality in a nation-wide cohort of people with type 1 diabetes in Scotland and to compare patterns over time and with the general population. METHODS: A retrospective cohort study was performed using data for people with type 1 diabetes from a population-based register linked to mortality records. Socio-economic status was derived from quintiles of an area-based measure: the Scottish Index of Multiple Deprivation. Sex-specific directly age-standardized mortality rates for each Scottish Index of Multiple Deprivation quintile and rate ratios comparing the most vs least deprived quintile were calculated for two time periods: 2006-2010 and 2011-2015. Data for the population without type 1 diabetes between 2011 and 2015 were available for comparison. RESULTS: Data for 3802 deaths among 33 547 people with type 1 diabetes were available. The age-standardized mortality rate per 1000 person-years decreased over time (from 2006-2010 to 2011-2015) for men and women with type 1 diabetes: 24.8 to 20.2 and 22.5 to 17.6, respectively. Mortality in populations with and without type 1 diabetes was generally higher for men than women and was inversely associated with socio-economic status. Rate ratios for the most vs least deprived groups increased over time among people with type 1 diabetes (men: 2.49 to 2.81; women: 1.92 to 2.86) and were higher than among populations without type 1 diabetes in 2011-2015 (men: 2.06; women: 1.66). CONCLUSIONS: Socio-economic deprivation was associated with a steeper mortality gradient in people with type 1 diabetes than in the population without type 1 diabetes in Scotland. Age-standardized mortality has decreased over time but socio-economic inequalities may be increasing.

The effect of DAFNE education, continuous subcutaneous insulin infusion, or both in a population with type 1 diabetes in Scotland.

AIM: To investigate the effect of DAFNE and continuous subcutaneous insulin infusion in clinical practice. METHODS: Within NHS Lothian, continuous subcutaneous insulin infusion started in 2004 and DAFNE education began in 2006. We extracted anonymized data from the national database for all those aged > 18 years with type 1 diabetes having a Dose Adjustment For Normal Eating course or continuous subcutaneous insulin infusion start date (n = 4617). RESULTS: In total, 956 persons received DAFNE education, and 505 had received an insulin pump, 208 of whom had DAFNE education followed by insulin pump. Mean (SD) HbA1c before DAFNE education was 68 (15) mmol/mol (8.4% [1.4%]) and 66 (13) mmol/mol (8.2% [1.2%]) before continuous subcutaneous insulin infusion. In the year following DAFNE education, the mean fall in within-person HbA1c was 3.8 mmol/mol (95% CI 4.0 to 3.4; 0.3% [0.4% to 0.3%]). Those with the poorest control (HbA1c ≥ 85 mmol/mol [9.9%]) experienced the largest decline (15.7 mmol/mol [1.4%]). Those in the lowest HbA1c band at initiation (< 53 mmol/mmol [7.0%]) experienced a rise. In the year following continuous subcutaneous insulin infusion initiation there was a mean fall in within-person HbA1c of 6.6 mmol/mol (6.8 to 6.4; 0.6% [0.6% to 0.6%]). In those with the poorest control (HbA1c ≥ 85 mmol/mol [9.9%]), the mean fall in HbA1c was 22.2 mmol/mol (23 to 21; 2.0% [2.1% to 1.9%]). Continuous subcutaneous insulin infusion effectiveness was not different with or without DAFNE education. The effects of both interventions were sustained over 5 years. CONCLUSIONS: Both DAFNE education and insulin pump therapy had the greatest effect on HbA1c in those with higher baseline values. There was little difference to attained HbA1c when Dose Adjustment For Normal Eating education was introduced before insulin pump therapy.

Associations between weight change and biomarkers of cardiometabolic risk in South Asians: secondary analyses of the PODOSA trial.

BACKGROUND/OBJECTIVES: The association of weight changes with cardiometabolic biomarkers in South Asians has been sparsely studied. SUBJECTS/METHODS: We measured cardiometabolic biomarkers at baseline and after 3 years in the Prevention of Diabetes and Obesity in South Asians Trial. We investigated the effect of a lifestyle intervention on biomarkers in the randomized groups. In addition, treating the population as a single cohort, we estimated the association between change in weight and change in biomarkers. RESULTS: Complete data were available at baseline and after 3 years in 151 participants. At 3 years, there was an adjusted mean reduction of 1·44 kg (95% confidence interval (95% CI): 0.18-2.71) in weight and 1.59 cm (95% CI: 0.08-3.09) in waist circumference in the intervention arm as compared with the control arm. There was no clear evidence of difference between the intervention and control arms in change of mean value of any biomarker. As a single cohort, every 1 kg weight reduction during follow-up was associated with a reduction in triglycerides (-1.3%, P=0.048), alanine aminotransferase (-2.5%, P=0.032), gamma-glutamyl transferase (-2.2%, P=0.040), leptin (-6.5%, P<0.0001), insulin (-3.7%, P=0.0005), fasting glucose (-0.8%, P=0.0071), 2-h glucose (-2.3%, P=0.0002) and Homeostatic Model Assessment of insulin resistance (HOMA-IR: -4.5%, P=0.0002). There was no evidence of associations with other lipid measures, tissue plasminogen activator, markers of inflammation or blood pressure. CONCLUSIONS: We demonstrate that modest weight decrease in SAs is associated with improvements in markers of total and ectopic fat as well as insulin resistance and glycaemia in South Asians at risk of diabetes. Future trials with more intensive weight change are needed to extend these findings.

Glycaemic control of Type 1 diabetes in clinical practice early in the 21st century: an international comparison.

AIMS: Improving glycaemic control in people with Type 1 diabetes is known to reduce complications. Our aim was to compare glycaemic control among people with Type 1 diabetes using data gathered in regional or national registries. METHODS: Data were obtained for children and/or adults with Type 1 diabetes from the following countries (or regions): Western Australia, Austria, Denmark, England, Champagne-Ardenne (France), Germany, Epirus, Thessaly and Thessaloniki (Greece), Galway (Ireland), several Italian regions, Latvia, Rotterdam (The Netherlands), Otago (New Zealand), Norway, Northern Ireland, Scotland, Sweden, Volyn (Ukraine), USA and Wales) from population or clinic-based registries. The sample size with available data varied from 355 to 173 880. Proportions with HbA1c < 58 mmol/mol (< 7.5%) and ≥ 75 mmol/mol (≥ 9.0%) were compared by age and sex. RESULTS: Data were available for 324 501 people. The proportions with HbA1c 58 mmol/mol (< 7.5%) varied from 15.7% to 46.4% among 44 058 people aged < 15 years, from 8.9% to 49.5% among 50 766 people aged 15-24 years and from 20.5% to 53.6% among 229 677 people aged ≥ 25 years. Sex differences in glycaemic control were small. Proportions of people using insulin pumps varied between the 12 sources with data available. CONCLUSION: These results suggest that there are substantial variations in glycaemic control among people with Type 1 diabetes between the data sources and that there is room for improvement in all populations, especially in young adults.

Factors associated with statin treatment for the primary prevention of cardiovascular disease in people within 2 years following diagnosis of diabetes in Scotland, 2006-2008.

AIM: To describe characteristics associated with statin prescribing for the primary prevention of cardiovascular disease in people with newly diagnosed diabetes. METHODS: Data from the Scottish Care Information-Diabetes Collaboration data set for 2006-2008 were used. This data set contains socio-demographic and prescribing data for over 99% of people with diagnosed diabetes in Scotland. Analyses were conducted on people aged over 40 years diagnosed with Type 1 or Type 2 diabetes between 2006 and 2008 with complete data and no previous history of cardiovascular or statin prescription. Logistic regression was used to calculate odds ratios for statin prescription in the 2 years following diagnosis of diabetes. RESULTS: There were 7157 men and 5601 women who met the inclusion criteria, 68% of whom had a statin prescription recorded in the 2 years following diagnosis of diabetes. The proportions receiving statins were lower above 65 years of age in men and 75 years of age in women. People with Type 1 diabetes had lower odds of receiving statins than people with Type 2 diabetes [odds ratio (95% CI) 0.42 (0.29-0.61) for men and 0.48 (0.28-0.81) for women, after adjustment for age, BMI, smoking status, cholesterol level and deprivation]. Higher total cholesterol, BMI and being a current smoker were associated with greater odds of statin prescription. CONCLUSION: Approximately one third of the study population had no record of statin prescription during the 2 years after diagnosis of diabetes. Cardiovascular disease risk reduction opportunities may be missed in some of these people.

Anomalous thermal contraction of the first coordination shell in metallic alloy liquids.

Except for a few anomalous solids and liquids, materials expand upon heating. For liquids, this should be reflected as a shift in the peak positions in the pair correlation function, g(r), to higher r. Here, we present the results of a detailed study of the volume thermal expansion coefficients and the temperature dependences of g(r) for a large number of binary, ternary, and quaternary liquids in the equilibrium and supercooled (metastable liquid below the liquidus temperature) states. The data were obtained from x-ray scattering and volume measurements on levitated liquids using the electrostatic levitation technique. Although the volumes of all liquids expand with increasing temperature, the peak positions in g(r) for the first coordination shells contract for the majority of alloy liquids studied. The second and third peaks in g(r) expand, but at rates different from those expected from the volume expansion. This behavior is explained qualitatively in terms of changes in the coordination numbers and bond-lengths as clusters in liquids break up with increasing temperature.

Culturally adapting the prevention of diabetes and obesity in South Asians (PODOSA) trial.

Type 2 diabetes is extremely common in South Asians, e.g. in men from Pakistani and Indian populations it is about three times as likely as in the general population in England, despite similarities in body mass index. Lifestyle interventions reduce the incidence of diabetes. Trials in Europe and North America have not, however, reported on the impact on South Asian populations separately or provided the details of their cross-cultural adaptation processes. Prevention of diabetes and obesity in South Asians (PODOSA) is a randomized, controlled trial in Scotland of an adapted, lifestyle intervention aimed at reducing weight and increasing physical activity to reduce type 2 diabetes in Indians and Pakistanis. The trial was adapted from the Finnish Diabetes Prevention Study. We describe, reflect on and discuss the following key issues: The core adaptations to the trial design, particularly the delivery of the intervention in homes by dietitians rather than in clinics. The use of both a multilingual panel and professional translators to help translate and/or develop materials. The processes and challenges of phonetic translation. How intervention resources were adapted, modified, newly developed and translated into Urdu and Gurmukhi (written Punjabi). The insights gained in PODOSA (including time pressures on investigators, imperfections in the adaptation process, the power of verbal rather than written information, the utilization of English and the mother-tongue languages simultaneously by participants and the costs) might help the research community, given the challenge of health promotion in multi-ethnic, urban societies.

Type 2 diabetes, socioeconomic status and risk of cancer in Scotland 2001-2007.

AIMS/HYPOTHESIS: The objective of this study was to use Scottish national data to assess the influence of type 2 diabetes on the risk of cancer at 16 different sites, while specifically investigating the role of confounding by socioeconomic status in the diabetes-cancer relationship. METHODS: All people in Scotland aged 55-79 years diagnosed with any of the cancers of interest during the period 2001-2007 were identified and classified by the presence/absence of co-morbid type 2 diabetes. The influence of diabetes on cancer risk for each site was assessed via Poisson regression, initially with adjustment for age only, then adjusted for both age and socioeconomic status. RESULTS: There were 4,285 incident cancers in people with type 2 diabetes. RR for any cancers (adjusted for age only) was 1.11 (95% CI 1.05, 1.17) for men and 1.33 (1.28, 1.40) for women. Corresponding values after additional adjustment for socioeconomic status were 1.10 (1.04, 1.15) and 1.31 (1.25, 1.38), respectively. RRs for individual cancer sites varied markedly. CONCLUSIONS/INTERPRETATION: Socioeconomic status was found to have little influence on the association between type 2 diabetes and cancer.

Predicted impact of extending the screening interval for diabetic retinopathy: the Scottish Diabetic Retinopathy Screening programme.

AIMS/HYPOTHESIS: The aim of our study was to identify subgroups of patients attending the Scottish Diabetic Retinopathy Screening (DRS) programme who might safely move from annual to two yearly retinopathy screening. METHODS: This was a retrospective cohort study of screening data from the DRS programme collected between 2005 and 2011 for people aged ≥12 years with type 1 or type 2 diabetes in Scotland. We used hidden Markov models to calculate the probabilities of transitions to referable diabetic retinopathy (referable background or proliferative retinopathy) or referable maculopathy. RESULTS: The study included 155,114 individuals with no referable diabetic retinopathy or maculopathy at their first DRS examination and with one or more further DRS examinations. There were 11,275 incident cases of referable diabetic eye disease (9,204 referable maculopathy, 2,071 referable background or proliferative retinopathy). The observed transitions to referable background or proliferative retinopathy were lower for people with no visible retinopathy vs mild background retinopathy at their prior examination (respectively, 1.2% vs 8.1% for type 1 diabetes and 0.6% vs 5.1% for type 2 diabetes). The lowest probability for transitioning to referable background or proliferative retinopathy was among people with two consecutive screens showing no visible retinopathy, where the probability was <0.3% for type 1 and <0.2% for type 2 diabetes at 2 years. CONCLUSIONS/INTERPRETATION: Transition rates to referable diabetic eye disease were lowest among people with type 2 diabetes and two consecutive screens showing no visible retinopathy. If such people had been offered two yearly screening the DRS service would have needed to screen 40% fewer people in 2009.

External validity of randomized controlled trials of glycaemic control and vascular disease: how representative are participants?

AIMS: To describe the proportion of people with Type 2 diabetes living in Scotland who meet eligibility criteria for inclusion in several large randomized controlled trials of glycaemic control to inform physicians and guideline developers about the generalizibility of trial results. METHODS: A literature review was performed to identify large trials assessing the impact of glycaemic control on risk of macrovascular disease. Inclusion and exclusion criteria from each trial were applied to data on the population of people with a diagnosis of Type 2 diabetes living in Scotland in 2008 (n = 180,590) in a population-based cross-sectional study and the number and proportion of people eligible for each trial was determined. RESULTS: Seven trials were identified. The proportion of people with Type 2 diabetes who met the eligibility criteria for the trials ranged from 3.5 to 50.7%. Trial participants were younger at age of diagnosis of diabetes and at time of trial recruitment than in the Scottish study population. The application of upper age criteria excluded the largest proportion of patients, with up to 39% of people with Type 2 diabetes ineligible for a trial with the most stringent criteria based on age alone. CONCLUSIONS: We found that many of the large trials of glycaemic control among people with Type 2 diabetes have limited external validity when applied to a population-based cohort of people with Type 2 diabetes. In particular, the age distribution of trial participants often does not reflect that of people with Type 2 diabetes in a contemporary British population.

Cardiorespiratory coupling in the bottlenose dolphin (Tursiops truncatus).

Introduction: The bottlenose dolphin (Tursiops truncatus) is an intermittent breather, where the breath begins with an exhalation followed by inhalation and an extended inter-breath interval ranging from 10 to 40 s. Breathing has been shown to alter both the instantaneous heart rate (if H) and stroke volume (iSV) in the bottlenose dolphin, with a transitory ventilatory tachycardia following the breath, and an exponential decrease to a stable if H around 40 beats • min-1 during the inter-breath period. As the total breath duration in the dolphin is around 1 s, it is not possible to assess the contribution of exhalation and inhalation to these changes in cardiac function during normal breathing. Methods: In the current study, we evaluated the if H response by separating expiration and inspiration of a breath, which allowed us to distinguish their respective contribution to the changes in if H. We studied 3 individual male bottlenose dolphins trained to hold their breath between the different respiratory phases (expiration and inhalation). Results: Our data show that inspiration causes an increase in if H, while expiration appears to result in a decrease in if H. Discussion: These data provide improved understanding of the cardiorespiratory coupling in dolphins, and show how both exhalation and inhalation alters if H.

Evaluating feasibility of functional near-infrared spectroscopy in dolphins.

Significance: Using functional near-infrared spectroscopy (fNIRS) in bottlenose dolphins (Tursiops truncatus) could help to understand how echolocating animals perceive their environment and how they focus on specific auditory objects, such as fish, in noisy marine settings. Aim: To test the feasibility of near-infrared spectroscopy (NIRS) in medium-sized marine mammals, such as dolphins, we modeled the light propagation with computational tools to determine the wavelengths, optode locations, and separation distances that maximize sensitivity to brain tissue. Approach: Using frequency-domain NIRS, we measured the absorption and reduced scattering coefficient of dolphin sculp. We assigned muscle, bone, and brain optical properties from the literature and modeled light propagation in a spatially accurate and biologically relevant model of a dolphin head, using finite-element modeling. We assessed tissue sensitivities for a range of wavelengths (600 to 1700 nm), source-detector distances (50 to 120 mm), and animal sizes (juvenile model 25% smaller than adult). Results: We found that the wavelengths most suitable for imaging the brain fell into two ranges: 700 to 900 nm and 1100 to 1150 nm. The optimal location for brain sensing positioned the center point between source and detector 30 to 50 mm caudal of the blowhole and at an angle 45 deg to 90 deg lateral off the midsagittal plane. Brain tissue sensitivity comparable to human measurements appears achievable only for smaller animals, such as juvenile bottlenose dolphins or smaller species of cetaceans, such as porpoises, or with source-detector separations ≫100 mm in adult dolphins. Conclusions: Brain measurements in juvenile or subadult dolphins, or smaller dolphin species, may be possible using specialized fNIRS devices that support optode separations of >100 mm. We speculate that many measurement repetitions will be required to overcome hemodynamic signals originating predominantly from the muscle layer above the skull. NIRS measurements of muscle tissue are feasible today with source-detector separations of 50 mm, or even less.

Self-calibrated pulse oximetry algorithm based on photon pathlength change and the application in human freedivers.

Significance: Pulse oximetry estimates the arterial oxygen saturation of hemoglobin (SaO2) based on relative changes in light intensity at the cardiac frequency. Commercial pulse oximeters require empirical calibration on healthy volunteers, resulting in limited accuracy at low oxygen levels. An accurate, self-calibrated method for estimating SaO2 is needed to improve patient monitoring and diagnosis. Aim: Given the challenges of calibration at low SaO2 levels, we pursued the creation of a self-calibrated algorithm that can effectively estimate SaO2 across its full range. Our primary objective was to design and validate our calibration-free method using data collected from human subjects. Approach: We developed an algorithm based on diffuse optical spectroscopy measurements of cardiac pulses and the modified Beer-Lambert law (mBLL). Recognizing that the photon mean pathlength (⟨L⟩) varies with SaO2 related absorption changes, our algorithm aligns/fits the normalized ⟨L⟩ (across wavelengths) obtained from optical measurements with its analytical representation. We tested the algorithm with human freedivers performing breath-hold dives. A continuous-wave near-infrared spectroscopy probe was attached to their foreheads, and an arterial cannula was inserted in the radial artery to collect arterial blood samples at different stages of the dive. These samples provided ground-truth SaO2 via a blood gas analyzer, enabling us to evaluate the accuracy of SaO2 estimation derived from the NIRS measurement using our self-calibrated algorithm. Results: The self-calibrated algorithm significantly outperformed the conventional method (mBLL with a constant ⟨L⟩ ratio) for SaO2 estimation through the diving period. Analyzing 23 ground-truth SaO2 data points ranging from 41% to 100%, the average absolute difference between the estimated SaO2 and the ground truth SaO2 is 4.23%±5.16% for our algorithm, significantly lower than the 11.25%±13.74% observed with the conventional approach. Conclusions: By factoring in the variations in the spectral shape of ⟨L⟩ relative to SaO2, our self-calibrated algorithm enables accurate SaO2 estimation, even in subjects with low SaO2 levels.

Area-based socioeconomic status, type 2 diabetes and cardiovascular mortality in Scotland.

AIMS/HYPOTHESIS: The aim of this study was to explore the relationships between type 2 diabetes mellitus, area-based socioeconomic status (SES) and cardiovascular disease mortality in Scotland. METHODS: We used an area-based measure of SES, Scottish national diabetes register data linked to mortality records, and general population cause-specific mortality data to investigate the relationships between SES, type 2 diabetes and mortality from ischaemic heart disease (IHD) and cerebrovascular disease (CbVD), for 2001-2007. We used negative binomial regression to obtain age-adjusted RRs of mortality (by sex), comparing people with type 2 diabetes with the non-diabetic population. RESULTS: Among 216,652 people aged 40 years or older with type 2 diabetes (980,687 person-years), there were 10,554 IHD deaths and 4,378 CbVD deaths. Age-standardised mortality increased with increasing deprivation, and was higher among men. IHD mortality RRs were highest among the least deprived quintile and lowest in the most deprived quintile (men: least deprived, RR 1.94 [95% CI 1.61, 2.33]; most deprived, RR 1.46 [95% CI 1.23, 1.74]) and were higher in women than men (women: least deprived, RR 2.84 [95% CI 2.12, 3.80]; most deprived, RR 2.04 [95% CI 1.55, 2.69]). A similar, weaker, pattern was observed for cerebrovascular mortality. CONCLUSIONS/INTERPRETATION: Absolute risk of cardiovascular mortality is higher in people with diabetes than in the non-diabetic population and increases with increasing deprivation. The relative impact of diabetes on cardiovascular mortality differs by SES, and further efforts to reduce cardiovascular risk both in deprived groups and people with diabetes are required. Prevention of diabetes may reduce socioeconomic health inequalities.

The effect of deprivation and HbA1c on admission to hospital for diabetic ketoacidosis in type 1 diabetes.

AIMS/HYPOTHESIS: Diabetic ketoacidosis is a potentially life-threatening complication of diabetes and has a strong relationship with HbA(1c). We examined how socioeconomic group affects the likelihood of admission to hospital for diabetic ketoacidosis. METHODS: The Scottish Care Information - Diabetes Collaboration (SCI-DC), a dynamic national register of all cases of diagnosed diabetes in Scotland, was linked to national data on hospital admissions. We identified 24,750 people with type 1 diabetes between January 2005 and December 2007. We assessed the relationship between HbA(1c) and quintiles of deprivation with hospital admissions for diabetic ketoacidosis in people with type 1 diabetes adjusting for patient characteristics. RESULTS: We identified 23,479 people with type 1 diabetes who had complete recording of covariates. Deprivation had a substantial effect on odds of admission to hospital for diabetic ketoacidosis (OR 4.51, 95% CI 3.73, 5.46 in the most deprived quintile compared with the least deprived). This effect persisted after the inclusion of HbA(1c) and other risk factors (OR 2.81, 95% CI 2.32, 3.39). Men had a reduced risk of admission to hospital for diabetic ketoacidosis (OR 0.71, 95% CI 0.63, 0.79) and those with a history of smoking had increased odds of admission to hospital for diabetic ketoacidosis by a factor of 1.55 (95% CI 1.36, 1.78). CONCLUSIONS/INTERPRETATION: Women, smokers, those with high HbA(1c) and those living in more deprived areas have an increased risk of admission to hospital for diabetic ketoacidosis. The effect of deprivation was present even after inclusion of other risk factors. This work highlights that those in poorer areas of the community with high HbA(1c) represent a group who might be usefully supported to try to reduce hospital admissions.