Coronavirus seasonality, respiratory infections and weather.

BACKGROUND: The survival of coronaviruses are influenced by weather conditions and seasonal coronaviruses are more common in winter months. We examine the seasonality of respiratory infections in England and Wales and the associations between weather parameters and seasonal coronavirus cases. METHODS: Respiratory virus disease data for England and Wales between 1989 and 2019 was extracted from the Second-Generation Surveillance System (SGSS) database used for routine surveillance. Seasonal coronaviruses from 2012 to 2019 were compared to daily average weather parameters for the period before the patient's specimen date with a range of lag periods. RESULTS: The seasonal distribution of 985,524 viral infections in England and Wales (1989-2019) showed coronavirus infections had a similar seasonal distribution to influenza A and bocavirus, with a winter peak between weeks 2 to 8. Ninety percent of infections occurred where the daily mean ambient temperatures were below 10 °C; where daily average global radiation exceeded 500 kJ/m2/h; where sunshine was less than 5 h per day; or where relative humidity was above 80%. Coronavirus infections were significantly more common where daily average global radiation was under 300 kJ/m2/h (OR 4.3; CI 3.9-4.6; p < 0.001); where average relative humidity was over 84% (OR 1.9; CI 3.9-4.6; p < 0.001); where average air temperature was below 10 °C (OR 6.7; CI 6.1-7.3; p < 0.001) or where sunshine was below 4 h (OR 2.4; CI 2.2-2.6; p < 0.001) when compared to the distribution of weather values for the same time period. Seasonal coronavirus infections in children under 3 years old were more frequent at the start of an annual epidemic than at the end, suggesting that the size of the susceptible child population may be important in the annual cycle. CONCLUSIONS: The dynamics of seasonal coronaviruses reflect immunological, weather, social and travel drivers of infection. Evidence from studies on different coronaviruses suggest that low temperature and low radiation/sunlight favour survival. This implies a seasonal increase in SARS-CoV-2 may occur in the UK and countries with a similar climate as a result of an increase in the R0 associated with reduced temperatures and solar radiation. Increased measures to reduce transmission will need to be introduced in winter months for COVID-19.

Influence of temperature on prevalence of health and welfare conditions in pigs: time-series analysis of pig abattoir inspection data in England and Wales.

The prevalence of many diseases in pigs displays seasonal distributions. Despite growing concerns about the impacts of climate change, we do not yet have a good understanding of the role that weather factors play in explaining such seasonal patterns. In this study, national and county-level aggregated abattoir inspection data were assessed for England and Wales during 2010-2015. Seasonally-adjusted relationships were characterised between weekly ambient maximum temperature and the prevalence of both respiratory conditions and tail biting detected at slaughter. The prevalence of respiratory conditions showed cyclical annual patterns with peaks in the summer months and troughs in the winter months each year. However, there were no obvious associations with either high or low temperatures. The prevalence of tail biting generally increased as temperatures decreased, but associations were not supported by statistical evidence: across all counties there was a relative risk of 1.028 (95% CI 0.776-1.363) for every 1 °C fall in temperature. Whilst the seasonal patterns observed in this study are similar to those reported in previous studies, the lack of statistical evidence for an explicit association with ambient temperature may possibly be explained by the lack of information on date of disease onset. There is also the possibility that other time-varying factors not investigated here may be driving some of the seasonal patterns.

The effect of ambient temperature on type-2-diabetes: case-crossover analysis of 4+ million GP consultations across England.

BACKGROUND: Given the double jeopardy of global increases in rates of obesity and climate change, it is increasingly important to recognise the dangers posed to diabetic patients during periods of extreme weather. We aimed to characterise the associations between ambient temperature and general medical practitioner consultations made by a cohort of type-2 diabetic patients. Evidence on the effects of temperature variation in the primary care setting is currently limited. METHODS: Case-crossover analysis of 4,474,943 consultations in England during 2012-2014, linked to localised temperature at place of residence for each patient. Conditional logistic regression was used to assess associations between each temperature-related consultation and control days matched on day-of-week. RESULTS: There was an increased odds of seeking medical consultation associated with high temperatures: Odds ratio (OR) = 1.097 (95% confidence interval = 1.041, 1.156) per 1 °C increase above 22 °C. Odds during low temperatures below 0 °C were also significantly raised: OR = 1.024 (1.019, 1.030). Heat-related consultations were particularly high among diabetics with cardiovascular comorbidities: OR = 1.171 (1.031, 1.331), but there was no heightened risk with renal failure or neuropathy comorbidities. Surprisingly, lower odds of heat-related consultation were associated with the use of diuretics, anticholinergics, antipsychotics or antidepressants compared to non-use, especially among those with cardiovascular comorbidities, although differences were not statistically significant. CONCLUSIONS: Type-2 diabetic patients are at increased odds of medical consultation during days of temperature extremes, especially during hot weather. The common assumption that certain medication use heightens the risk of heat illness was not borne-out by our study on diabetics in a primary care setting and such advice may need to be reconsidered in heat protection plans.

Public health vulnerability to wintertime weather: time-series regression and episode analyses of national mortality and morbidity databases to inform the Cold Weather Plan for England.

OBJECTIVES: To inform development of Public Health England's Cold Weather Plan (CWP) by characterizing pre-existing relationships between wintertime weather and mortality and morbidity outcomes, and identification of groups most at risk. STUDY DESIGN: Time-series regression analysis and episode analysis of daily mortality, emergency hospital admissions, and accident and emergency visits for each region of England. METHODS: Seasonally-adjusted Poisson regression models estimating the percent change in daily health events per 1 °C fall in temperature or during individual episodes of extreme weather. RESULTS: Adverse cold effects were observed in all regions, with the North East, North West and London having the greatest risk of cold-related mortality. Nationally, there was a 3.44% (95% CI: 3.01, 3.87) increase in all-cause deaths and 0.78% (95% CI: 0.53, 1.04) increase in all-cause emergency admissions for every 1 °C drop in temperature below identified thresholds. The very elderly and people with COPD were most at risk from low temperatures. A&E visits for fractures were elevated during heavy snowfall periods, with adults (16-64 years) being the most sensitive age-group. Since even moderately cold days are associated with adverse health effects, by far the greatest health burdens of cold weather fell outside of the alert periods currently used in the CWP. CONCLUSIONS: Our findings indicate that levels 0 ('year round planning') and 1 ('winter preparedness and action') are crucial components of the CWP in comparison to the alerts. Those most vulnerable during winter may vary depending on the type of weather conditions being experienced. Recommendations are made for the CWP.

Evaluation of the cold weather plan for England: modelling of cost-effectiveness.

OBJECTIVE: To determine the conditions under which the Cold Weather Plan (CWP) for England is likely to prove cost-effective in order to inform the development of the CWP in the short term before direct data on costs and benefits can be collected. STUDY DESIGN: Mathematical modelling study undertaken in the absence of direct epidemiological evidence on the effect of the CWP in reducing cold-related mortality and morbidity, and limited data or on its costs. METHODS: The model comprised a simulated temperature time series based on historical data; epidemiologically-derived relationships between temperature, and mortality and morbidity; and information on baseline unit costs of contacts with health care and community care services. Cost-effectiveness was assessed assuming varying levels of protection against cold-related burdens, coverage of the vulnerable population and willingness-to-pay criteria. RESULTS: Simulations showed that the CWP is likely to be cost effective under some scenarios at the high end of the willingness to pay threshold used by National Institute for Health and Care Excellence (NICE) in England, but these results are sensitive to assumptions about the extent of implementation of the CWP at local level, and its assumed effectiveness when implemented. The incremental cost-effectiveness ratio varied from £29,754 to £75,875 per Quality Adjusted Life Year (QALY) gained. Conventional cost-effectiveness (<£30,000/QALY) was reached only when effective targeting of at-risk groups was assumed (i.e. need for low coverage (∼5%) of the population for targeted actions) and relatively high assumed effectiveness (>15%) in avoiding deaths and hospital admissions. CONCLUSIONS: Although the modelling relied on a large number of assumptions, this type of modelling is useful for understanding whether, and in what circumstances, untested plans are likely to be cost-effective before they are implemented and in the early period of implementation before direct data on cost-effectiveness have accrued. Steps can then be taken to optimize the relevant parameters as far as practicable during the early implementation period.

Ambient temperature and activation of implantable cardioverter defibrillators.

The degree to which weather influences the occurrence of serious cardiac arrhythmias is not fully understood. To investigate, we studied the timing of activation of implanted cardiac defibrillators (ICDs) in relation to daily outdoor temperatures using a fixed stratum case-crossover approach. All patients attending ICD clinics in London between 1995 and 2003 were recruited onto the study. Temperature exposure for each ICD patient was determined by linking each patient's postcode of residence to their nearest temperature monitoring station in London and the South of England. There were 5,038 activations during the study period. Graphical inspection of ICD activation against temperature suggested increased risk at lower but not higher temperatures. For every 1 °C decrease in ambient temperature, risk of ventricular arrhythmias up to 7 days later increased by 1.2 % (95 % CI -0.6 %, 2.9 %). In threshold models, risk of ventricular arrhythmias increased by 11.2 % (0.5 %, 23.1 %) for every 1° decrease in temperature below 2 °C. Patients over the age of 65 exhibited the highest risk. This large study suggests an inverse relationship between ambient outdoor temperature and risk of ventricular arrhythmias. The highest risk was found for patients over the age of 65. This provides evidence about a mechanism for some cases of low-temperature cardiac death, and suggests a possible strategy for reducing risk among selected cardiac patients by encouraging behaviour modification to minimise cold exposure.

Cold and heat waves in the United States.

Extreme cold and heat waves, characterized by a number of cold or hot days in succession, place a strain on people's cardiovascular and respiratory systems. The increase in deaths due to these waves may be greater than that predicted by extreme temperatures alone. We examined cold and heat waves in 99 US cities for 14 years (1987-2000) and investigated how the risk of death depended on the temperature threshold used to define a wave, and a wave's timing, duration and intensity. We defined cold and heat waves using temperatures above and below cold and heat thresholds for two or more days. We tried five cold thresholds using the first to fifth percentiles of temperature, and five heat thresholds using the 95-99 percentiles. The extra wave effects were estimated using a two-stage model to ensure that their effects were estimated after removing the general effects of temperature. The increases in deaths associated with cold waves were generally small and not statistically significant, and there was even evidence of a decreased risk during the coldest waves. Heat waves generally increased the risk of death, particularly for the hottest heat threshold. Cold waves of a colder intensity or longer duration were not more dangerous. Cold waves earlier in the cool season were more dangerous, as were heat waves earlier in the warm season. In general there was no increased risk of death during cold waves above the known increased risk associated with cold temperatures. Cold or heat waves earlier in the cool or warm season may be more dangerous because of a build up in the susceptible pool or a lack of preparedness for extreme temperatures.

Temperature-dependent transmission of rotavirus in Great Britain and The Netherlands.

In Europe, rotavirus gastroenteritis peaks in late winter or early spring suggesting a role for weather factors in transmission of the virus. In this study, multivariate regression models adapted for time-series data were used to investigate effects of temperature, humidity and rainfall on reported rotavirus infections and the infection-rate parameter, a derived measure of infection transmission that takes into account population immunity, in England, Wales, Scotland and The Netherlands. Delayed effects of weather were investigated by introducing lagged weather terms into the model. Meta-regression was used to pool together country-specific estimates. There was a 13 per cent (95% confidence interval (CI), 11-15%) decrease in reported infections per 1 degrees C increase in temperature above a threshold of 5 degrees C and a 4 per cent (95% CI, 3-5%) decrease in the infection-rate parameter per 1 degrees C increase in temperature across the whole temperature range. The effect of temperature was immediate for the infection-rate parameter but delayed by up to four weeks for reported infections. There was no overall effect of humidity or rainfall. There is a direct and simple relationship between cold weather and rotavirus transmission in Great Britain and The Netherlands. The more complex and delayed temperature effect on disease incidence is likely to be mediated through the effects of weather on transmission.

Modelling the non-linear multiple-lag effects of ambient temperature on mortality in Santiago and Palermo: a constrained segmented distributed lag approach.

OBJECTIVES: Exposure to ambient temperature can affect mortality levels for days or weeks following exposure, making modelling such effects in regression analysis of daily time-series data complex. METHODS: We propose a new approach involving a multi-lag segmented approximation to account for the non-linear effect of temperature and the use of two different penalized spline bases to model the distributed lag of both heat and cold exposure. Compared with standard splines, the novel penalized framework is more flexible at short lags where change in coefficients is greatest, and selection of the maximum lag appears substantially less important in determining the overall pattern of the effect. RESULTS: Applying the approach to daily mortality in Santiago (Chile) and Palermo (Italy), we observed a heat effect that was mostly immediate and followed by negative estimates consistent with short-term mortality displacement (harvesting). Cold effects were mostly positively sustained and more evenly distributed across the 60-day analysis period: in Santiago we estimated an overall increase in deaths of 2.36% (95% CI 0.26% to 4.51%) in the 65+ age group associated with every 1 degrees C decrease below the cold threshold, and an increase of 1.11% (0.09% to 2.14%) per 1 degrees C for Palermo. Heat effects for Palermo were much larger than for Santiago, and less harvesting of heat deaths was evident. The estimated heat thresholds were higher in Palermo than in Santiago. CONCLUSIONS: Our approach provides a flexible and precise method to quantify health effects of both heat and cold exposure at individual lags and to model the overall pattern of the delayed effect.

Heat-related and cold-related deaths in England and Wales: who is at risk?

BACKGROUND: Despite the high burden from exposure to both hot and cold weather each year in England and Wales, there has been relatively little investigation on who is most at risk, resulting in uncertainties in informing government interventions. OBJECTIVE: To determine the subgroups of the population that are most vulnerable to heat-related and cold-related mortality. METHODS: Ecological time-series study of daily mortality in all regions of England and Wales between 1993 and 2003, with postcode linkage of individual deaths to a UK database of all care and nursing homes, and 2001 UK census small-area indicators. RESULTS: A risk of mortality was observed for both heat and cold exposure in all regions, with the strongest heat effects in London and strongest cold effects in the Eastern region. For all regions, a mean relative risk of 1.03 (95% confidence interval (CI) 1.02 to 1.03) was estimated per degree increase above the heat threshold, defined as the 95th centile of the temperature distribution in each region, and 1.06 (95% CI 1.05 to 1.06) per degree decrease below the cold threshold (set at the 5th centile). Elderly people, particularly those in nursing and care homes, were most vulnerable. The greatest risk of heat mortality was observed for respiratory and external causes, and in women, which remained after control for age. Vulnerability to either heat or cold was not modified by deprivation, except in rural populations where cold effects were slightly stronger in more deprived areas. CONCLUSIONS: Interventions to reduce vulnerability to both hot and cold weather should target all elderly people. Specific interventions should also be developed for people in nursing and care homes as heat illness is easily preventable.

Temporal associations between daily counts of fungal spores and asthma exacerbations.

BACKGROUND: Outdoor aeroallergens are one of a number of environmental factors thought to precipitate asthma exacerbations. AIMS: To investigate the short term associations between daily fungal spore concentrations and indicators of daily asthma exacerbations in a large urban population. METHODS: Daily counts of visits for asthma to family physicians and hospital accident and emergency (A&E) departments and emergency hospital admissions in London 1992-93 were compiled. Daily concentrations of fungal spores (30 species), daily average temperature, humidity, and concentrations of pollen and outdoor air pollution were also compiled. The analysis was restricted to the period when fungal spores were most prevalent (June to mid October). Non-parametric regression time series methods were used to assess associations controlling for seasonality, day of week, and meteorological factors. The sensitivity of the findings to the inclusion of pollen and air pollution into the models was also assessed. RESULTS: In children aged 0-14 years the relative risks for increases in the number of A&E visits and hospital admissions associated with changes in fungal spore concentrations from the lower to upper quartiles were 1.06 (95% CI 0.94 to 1.18) and 1.07 (0.97 to 1.19) respectively. The addition of pollen or air pollutants had little impact on the observed associations. A number of individual spore taxa, in particular Alternaria, Epicoccum, Agrocybe, Mildews, and both coloured and colourless Basidiospores and Ascospores, were associated with increases in the number of emergency visits and hospital admissions for asthma, although the precision of these estimates were low. No evidence was found for associations in adults. CONCLUSIONS: Fungal spore concentrations may provoke or exacerbate asthma attacks in children resulting in visits to A&E departments and emergency hospital admissions. These findings were unlikely to be due to confounding by other environmental factors. The associations were comparable to those observed for ambient air pollution from similarly designed studies.

Syndromic surveillance use to detect the early effects of heat-waves: an analysis of NHS direct data in England.

OBJECTIVES: To investigate the effects of high ambient temperatures, including the summer 2003 heat-episode, on NHS Direct usage and its suitability as a surveillance tool in heat health warning systems. METHODS: Analyses of data on calls to NHS Direct in English Regions in the period Dec 2001-May 2004. Outcomes were daily rates of all symptomatic calls, and daily proportion of calls for selected causes (fever, vomiting, difficulty breathing, heat/sun-stroke) RESULTS: Total calls were moderately increased as environmental temperature increased; this effect was greatest in calls for young children and for fever. Total calls were moderately elevated during two summer heat episodes in 2003: calls specifically for heat/sun stroke increased acutely in response to these episodes. No association was apparent between environmental temperature and proportion of calls for vomiting and difficulty breathing. CONCLUSIONS: Calls to NHS Direct are sensitive to daily temperatures and extreme weather. NHS Direct is timely and has great potential in health surveillance. Calls for heat- and sun-stroke are now routinely monitored as part of the UK Heat-wave plan

Associations of cold temperatures with GP consultations for respiratory and cardiovascular disease amongst the elderly in London.

BACKGROUND: The relationships between cold temperatures and cardio-respiratory mortality in the elderly are well documented. We wished to determine whether similar relationships exist with consultations in the primary care setting and to assess the lag time at which the effects were observed. METHODS: Generalized additive models were used to regress time-series of daily numbers of general practitioner (GP) consultations by the elderly against temperature, after control for possible confounders and adjustment for overdispersion and serial correlation. Consultation data were available from between 38 452 and 42 772 registered patients aged >or=65 years from 45-47 London practices contributing to the General Practice Research Database between January 1992 and September 1995. RESULTS: There was little relationship between consultations for respiratory disease and mean temperature on the same day as the day of consultation. However, a strong association was apparent with temperature levels up to 15 days previously, with an increase in consultations being observed particularly as temperatures drop below 5 degrees C. Every 1 degrees C decrease in mean temperatures below 5 degrees C was associated with a 10.5% (95% CI: 7.6%, 13.4%) increase in all respiratory consultations. No relationship was observed between cold temperatures and GP consultations for cardiovascular disease. CONCLUSIONS: Our study suggests a delayed effect of a drop in temperature on consultations for respiratory disease in the primary care setting. Information such as this could be used to help prepare practices to anticipate increases in respiratory consultation rates associated with low temperatures.

Impact of hot temperatures on death in London: a time series approach.

STUDY OBJECTIVE: This study investigated the relation between heat and mortality in London to determine the temperature threshold at which death rates increase and to quantify the effect of extreme temperatures on mortality. DESIGN: Daily data on all cause mortality and temperature were obtained for a 21 year period and the relation between them investigated both graphically and by using non-parametric time series methods of analysis. SETTING: Greater London. PARTICIPANTS: Daily mortality counts in Greater London between January 1976 and December 1996. MAIN RESULTS: A plot of the basic mortality-temperature relation suggested that a rise in heat related deaths began at about 19 degrees C. Average temperatures above the 97th centile value of 21.5 degrees C (excluding those days from a 15 day "heatwave" period in 1976) resulted in an increase in deaths of 3.34% (95% CI 2.47% to 4.23%) for every one degree increase in average temperature above this value. It was found that the 1976 heatwave resulted in a particularly large number of deaths in comparison with other hot periods. CONCLUSIONS: These results suggest that heat related deaths in London may begin at relatively low temperatures. Hot days occurring in the early part of any year may have a larger effect than those occurring later on; and analysis of separate heatwave periods suggest that episodes of long duration and of highest temperature have the largest mortality effect.

Contrasting patterns of mortality and hospital admissions during hot weather and heat waves in Greater London, UK.

BACKGROUND: Epidemiological research has shown that mortality increases during hot weather and heat waves, but little is known about the effect on non-fatal outcomes in the UK. AIMS AND METHODS: The effects of hot weather and heat waves on emergency hospital admissions were investigated in Greater London, UK, for a range of causes and age groups. Time series analyses were conducted of daily emergency hospital admissions, 1 April 1994 to 31 March 2000, using autoregressive Poisson models with adjustment for long term trend, season, day of week, public holidays, the Christmas period, influenza, relative humidity, air pollution (ozone, PM10), and overdispersion. The effects of heat were modelled using the average of the daily mean temperature over the index and previous two days. RESULTS: There was no clear evidence of a relation between total emergency hospital admissions and high ambient temperatures, although there was evidence for heat related increases in emergency admissions for respiratory and renal disease, in children under 5, and for respiratory disease in the 75+ age group. During the heat wave of 29 July to 3 August 1995, hospital admissions showed a small non-significant increase: 2.6% (95% CI -2.2 to 7.6), while daily mortality rose by 10.8% (95% CI 2.8 to 19.3) after adjusting for time varying confounders. CONCLUSIONS: The impact of hot weather on mortality is not paralleled by similar magnitude increases in hospital admissions in the UK, which supports the hypothesis that many heat related deaths occur in people before they come to medical attention. This has evident implications for public health, and merits further enquiry.

Thunderstorm-associated asthma: the effect on GP consultations.

Evidence shows that asthma attacks can be brought on by adverse weather conditions such as those experienced during a thunderstorm; a prime example of such an occasion being a thunderstorm episode on 24 June 1994, which resulted in a well-documented increase in medical attendances made by those suffering with asthma and respiratory disorders. However, most of these studies have concerned admissions to accident and emergency departments. The aim of this paper was to ascertain whether a similar increase in consultations was observed in the primary care setting.

The value of short and simple measures to assess outcomes for patients of total hip replacement surgery.

OBJECTIVES: To evaluate the performance of a patient assessed outcome measure, the Oxford Hip Score, in a national study of primary hip replacement surgery. DESIGN: A survey of patients' health status before undergoing primary hip replacement surgery and three months and one year after surgery. SETTING: 143 hospitals in three NHS English regions. PATIENTS: 7151 patients admitted for primary total hip replacement surgery over a period of 13 months from September 1996. MAIN MEASURES: For patients, Oxford Hip Score and satisfaction with hip replacement and, for surgeons, American Anesthesiologists' Society (ASA) classification of physical status. RESULTS: The response rates to the postal questionnaire at three and 12 months follow up were 85.2% and 80.7%, respectively. Including all three administrations of the questionnaire, all except two items of the Oxford Hip Score were completed by 97% or more respondents and only one item at one administration appeared marginally to reduce the reliability of the score. The effect sizes for changes in the score from baseline to three months was 2.50 and to 12 months was 3.05. Patients rated by surgeons as being healthy preoperatively by the ASA classification were somewhat more likely to return a completed questionnaire at three months (79.4% versus 75.3%) and 12 months (72.4% versus 70.3%) than those rated as having poorer health. CONCLUSIONS: Overall there was little evidence of difficulties for patients in completing the Oxford Hip Score or of unreliable data, except in relation to one questionnaire item. The instrument was very responsive to change over time and score changes for the Oxford Hip Score related well to patients' satisfaction with their surgery. The instrument is an appropriate measure in terms of validity, responsiveness, and feasibility for evaluating total hip replacement from the

Primary total hip replacement: variations in patient management in Oxford & Anglia, Trent, Yorkshire & Northern 'regions'.

OBJECTIVES: To examine national practice, and variations in practice, concerning total hip replacement; in particular the choice of prosthesis and the involvement of consultants in NHS operations. DESIGN: Pre-operative survey of patients undergoing total hip replacement. SETTING: Five English regions serving combined population of 16.8 million people. SUBJECTS: 13,343 total hip replacement operations in one year commencing September 1996, either in NHS or private sector. MAIN OUTCOME MEASURES: Prosthesis used for surgery, status of surgeons involved in operation, use of laminar flow operating theatre. RESULTS: Prostheses without well documented 5-year survival were used in 5504 (58%) of 9417 operations for which information was available. The consultant was the operator in 4810 (64%) of 7499 NHS operations. In 1352 trainee-led operations, the consultant was present for only 637 (47%); this figure was 54% for trainees in years 1-4 of their training. Substantial variation between NHS consultant firms occurred both for use of prostheses with well documented survival data, and supervision of trainees by the consultant. CONCLUSIONS: This large study is the first attempt to describe national practice for primary total hip replacement. Substantial variation among consultant firms was observed for all indices of practice reported.

Association of mortality with high temperatures in a temperate climate: England and Wales.

BACKGROUND: It is well known that high ambient temperatures are associated with increased mortality, even in temperate climates, but some important details are unclear. In particular, how heat-mortality associations (for example, slopes and thresholds) vary by climate has previously been considered only qualitatively. METHODS: An ecological time-series regression analysis of daily counts of all-cause mortality and ambient temperature in summers between 1993 and 2006 in the 10 government regions was carried out, focusing on all-cause mortality and 2-day mean temperature (lags 0 and 1). RESULTS: All regions showed evidence of increased risk on the hottest days, but the specifics, in particular the threshold temperature at which adverse effects started, varied. Thresholds were at about the same centile temperatures (the 93rd, year-round) in all regions-hotter climates had higher threshold temperatures. Mean supra-threshold slope was 2.1%/°C (95% CI 1.6 to 2.6), but regions with higher summer temperatures showed greater slopes, a pattern well characterised by a linear model with mean summer temperature. These climate-based linear-threshold models capture most, but not all, the association; there was evidence for some non-linearity above thresholds, with slope increasing at highest temperatures. CONCLUSION: Effects of high daily summer temperatures on mortality in English regions are quite well approximated by threshold-linear models that can be predicted from the region's climate (93rd centile and mean summer temperature). It remains to be seen whether similar relationships fit other countries and climates or change over time, such as with climate change.