Interrupted Time Series Studies Research Articles

Long-term disease course, cost and prognosis of inflammatory bowel disease: epidemiological studies of a European and a Danish inception cohort.

Long-term disease course, cost and prognosis of inflammatory bowel disease: epidemiological studies of a European and a Danish inception cohort.

Examining the impact of the COVID-19 pandemic on hospital-associated Clostridioides difficile infection

Background: The epidemiology of Clostridioides difficile infection (CDI) is complex, and the COVID-19 pandemic has had extreme impacts on known risk factors such as comorbidity burden and antibiotic prescribing. However, whether these changes have affected the incidence of hospital-associated CDI (HA-CDI) remains unknown. We compared incidence and trends of HA-CDI before and after the pandemic onset, and we assessed the impact of changes in key CDI-related risk factors. Methods: We conducted an interrupted time-series study (March 2018–March 2021) of adult inpatients hospitalized 4 or more days with no known CDI on admission at a 576-bed academic medical center. Our primary outcome was monthly HA-CDI per 10,000 patient days. We performed segmented linear regression to compare the preinterruption trend in HA-CDI rate to the postinterruption slope and level change. We established a series of 30-day intervals before and after the interruption timepoint of March 23, 2020, which corresponds with the Oregon stay-at-home executive order. The data included 24 preinterruption time points and 12 postinterruption time points. We also assessed changes in slope and trend for known HA-CDI risk factors. Results: We included 34,592 inpatient encounters in our prepandemic period and 10,932 encounters in our postinterruption period. The mean prepandemic HA-CDI rate was 4.07 cases per 10,000 patient days. After the pandemic onset, the rate was 3.6 per 10,000 patient days. However, the observed differences in rate (both in terms of slope and level) were not statistically significant (P = .90 for level; P = .60 for slope change). We observed a significant decrease in admissions per 30 days (1,441 vs 911; level-change P < .0001) and a slight increase in the mean number of Elixhauser comorbidities (1.96 vs 2.07; level-change P = .05). We also observed significant increases in both frequency and intensity of antibiotic use, with an increase average days of therapy per encounter (5.8 vs 7.2; level-change P = .01; slope-change P < .0001) and in antibiotic spectrum index (ASI) points per antibiotic day (4.4 vs 4.9; P < .0001). We observed a consistent downward trend for case days of CDI colonization pressure per hospital day (preinterruption slope P < .0001), which remained consistent after the pandemic onset (P = 0.5 for postinterruption slope change) (Fig. 1). Conclusions: Despite significant increases in high-intensity antibiotic use and comorbidity burden, we did not observe significant differences in HA-CDI after the pandemic onset. This may be due to the significant decrease in colonization pressure in the postpandemic period. Further research is required to fully understand the impact of the pandemic-related changes onDisclosures: None

The impact of lidocaine plaster prescribing reduction strategies: A comparison of two national health services in Europe.

In 2017, two distinct interventions were implemented in Ireland and England to reduce prescribing of lidocaine medicated plasters. In Ireland, restrictions on reimbursement were introduced through implementation of an application system for reimbursement. In England, updated guidance on items which should not be routinely prescribed in primary care, including lidocaine plasters, was published. This study aims to compare how the interventions impacted prescribing of lidocaine plasters in these countries. We conducted an interrupted time-series study using general practice data. For Ireland, monthly dispensing data (2015-2019) from the means-tested General Medical Services (GMS) scheme was used. For England, data covered all patients. Outcomes were the rate of dispensings, quantity and costs of lidocaine plasters, and we modelled level and trend changes from the first full month of the policy/guidance change. Ireland had higher rates of lidocaine dispensings compared to England throughout the study period; this was 15.22/1000 population immediately pre-intervention, and there was equivalent to a 97.2% immediate reduction following the intervention. In England, the immediate pre-intervention dispensing rate was 0.36/1000, with an immediate reduction of 0.0251/1000 (a 5.8% decrease), followed by a small but significant decrease in the monthly trend relative to the pre-intervention trend of 0.0057 per month. Among two different interventions aiming to decrease low-value lidocaine plaster prescribing, there was a substantially larger impact in Ireland of reimbursement restriction compared to issuing guidance in England. However, this is in the context of much higher baseline rates of use in Ireland compared to England.

Evaluation of a Quality Improvement Bundle Aimed to Reduce Opioid Prescriptions After Cesarean Delivery: An Interrupted Time Series Study

(Can J Anesth/J Can Anesth. 2022;69:1007–1016) There are efforts from the medical community and the public to reduce the prescription of opioids in the United States and Canada. Quality improvement (QI) initiatives have been successfully used to reduce opioid prescriptions in patients undergoing cesarean delivery (CD). This study assessed opioid prescribing rates following a quality improvement initiative, hypothesizing there would be a lower rate of opioid prescription in post-CD patients following implementation of the QI bundle.

Value in Primary Care: Evidence from the Canadian Primary Care Sentinel Surveillance Network.

Primary care antimicrobial stewardship programs are virtually non-existent. Using electronic medical record (EMR) data for an interrupted time series study, the authors examined the relationship between antibiotic prescriptions for acute respiratory tract infections (RTIs) and the COVID-19 pandemic. The main outcome of the study was to gauge the proportion of RTI encounters with an antibiotic prescription. The pre-pandemic RTI antibiotic prescribing rate was 27.8%. During the COVID-19 pandemic, prescribing dropped significantly by 9.4% (p < 0.001). Almost 750,000 fewer patients could potentially avoid receiving an antibiotic prescription for RTI. The authors also discuss the value of EMR data; their use can help develop insights for health system improvement.

Long-Term Impact of a Smartphone App on Prescriber Adherence to Antibiotic Guidelines for Adult Patients With Community-Acquired Pneumonia: Interrupted Time-Series Study.

Mobile health platforms like smartphone apps that provide clinical guidelines are ubiquitous, yet their long-term impact on guideline adherence remains unclear. In 2016, an antibiotic guidelines app, called SCRIPT, was introduced in Auckland City Hospital, New Zealand, to provide local antibiotic guidelines to clinicians on their smartphones. We aimed to assess whether the provision of antibiotic guidelines in a smartphone app resulted in sustained changes in antibiotic guideline adherence by prescribers. We analyzed antibiotic guideline adherence rates during the first 24 hours of hospital admission in adults diagnosed with community-acquired pneumonia using an interrupted time-series study with 3 distinct periods post app implementation (ie, 3, 12, and 24 months). Adherence increased from 23% (46/200) at baseline to 31% (73/237) at 3 months and 34% (69/200) at 12 months, reducing to 31% (62/200) at 24 months post app implementation (P=.07 vs baseline). However, increased adherence was sustained in patients with pulmonary consolidation on x-ray (9/63, 14% at baseline; 23/77, 30% after 3 months; 32/92, 35% after 12 month; and 32/102, 31% after 24 months; P=.04 vs baseline). An antibiotic guidelines app increased overall adherence, but this was not sustained. In patients with pulmonary consolidation, the increased adherence was sustained.

COVID-19 pandemic and the quality of antibiotic use in primary care: an interrupted time-series study.

The coronavirus disease-19 pandemic and the related public health mitigation measures have impacted the transmission of infectious diseases; however, their impact on the use of antibacterials has not yet been extensively evaluated. This study evaluated the impact of the pandemic on the consumption patterns of antibacterials for systemic use in primary care in Portugal. An interrupted time-series analysis was performed using the autoregressive integrated moving average model of the antibacterials dispensed in the community pharmacies in Portugal from 1 January 2016 to 30 June 2022. Monthly rates of absolute consumption (all antibacterials for systemic use, and specifically penicillins; cephalosporins; macrolides, lincosamides, and streptogramins; and quinolones) and the relative consumption of antibacterials (penicillins sensitive to β-lactamase, penicillin combinations including β-lactamase inhibitors, third- and fourth-generation cephalosporins, fluoroquinolones, and the ratio of broad- to narrow-spectrum antibacterials) were estimated. Antibiotic consumption was expressed in defined daily doses per 1000 inhabitants per day (DID). In Portugal, the consumption of antibacterials (J01) declined sharply immediately after the beginning of the pandemic, having a significant reduction of >5 DID (P < .0001). A similar, short-term impact was found for penicillins (-2.920 DID; P < .0001); cephalosporins (-0.428 DID; P < .0001); macrolides, lincosamides, and streptogramins (-0.681 DID; P = .0021); and quinolones (-0.320 DID; P < .0001). A long-term increase was found for cephalosporins (+0.019 DID per month; P < .0001). Relative consumption changes were only found for third- and fourth-generation cephalosporins (0.0734%). Our study suggests that the coronavirus disease-19 pandemic may have resulted in a decrease in antibiotic use, with no significant changes in the relative dispense. Uncertainties regarding the long-term effects of the pandemic and its impact on the rates of resistance remain.

The influence of the COVID-19 pandemic on identifying HIV/AIDS cases in China: an interrupted time series study

The COVID-19 pandemic has caused significant global public health challenges, and impacted HIV testing and reporting worldwide. We aimed to estimate the impact of COVID-19 polices on identifying HIV/AIDS cases in China from 2020 to2022. We used an interrupted time series (ITS) design and seasonal autoregressive integrated moving average intervention (SARIMA Intervention) model. Monthly reported data on HIV/AIDS cases were extracted from the National Bureau of Disease Control and Prevention of China from January 2004 to August 2022. Data on Stringency Index (SI) and Economic Support Index (ESI) from January 22, 2020 to August 31, 2022 were extracted from the Oxford COVID-19 Government Response Tracker (OxCGRT). Using these, a SARIMA-Intervention model was constructed to evaluate the association between COVID-19 polices and monthly reported HIV/AIDS case numbers from January 2004 to August 2022 using auto.arima () function from R. The absolute percentage errors (APEs) compared the expected numbers generated by the SARIMA-Intervention model with actual numbers of HIV/AIDS, and was the primary outcome of this study. A second counterfactual model estimated HIV/AIDS case numbers if COVID-19 hadn't occurred in December 2019, and the mean difference between actual and predicted numbers were calculated. All statistical analyses were performed in R software (version 4.2.1) and EmpowerStats 2.0 and a P<0.05 was considered statistically significant. The SARIMA-Intervention model indicated HIV/AIDS monthly reported cases were inversely and significantly correlated with stricter lockdown and COVID-19 related polices (Coefficient for SI=-231.24, 95% CI:-383.17,-79.32) but not with economic support polices (Coefficient for ESI=124.27, 95% CI:-309.84, 558.38). APEs of the SARIMA-Intervention model for prediction of HIV/AIDS cases from January 2022 through August 2022, were-2.99, 5.08,-13.64,-34.04,-2.76,-1.52,-1.37 and-2.47 respectively, indicating good accuracy and underreporting of cases during COVID-19. The counterfactual model estimates between January 2020 and August 2022 an additional 1314 HIV/AIDS cases should have been established monthly if COVID-19 hadn't occurred. The COVID-19 pandemic influenced the allocation and acquisition of medical resources which impacted accurate monthly reporting of HIV in China. Interventions that promote continuous HIV testing and ensure the adequate provision of HIV services including remote delivery of HIV testing services (HIV self-testing) and online sexual counseling services are necessary during pandemics in future. Ministry of Science and Technology of the People's Republic of China (The grant number: 2020YFC0846300) and Fogarty International Center, National Institutes of Health, USA (The grant number: G11TW010941).

Impact assessment of a raw coal ban on maternal and child health outcomes in Ulaanbaatar: a protocol for an interrupted time series study

IntroductionDespite a decade of policy actions, Ulaanbaatar’s residents continue to be exposed to extreme levels of air pollution, a major public health concern, especially for vulnerable populations such as pregnant...

Changes in opioid prescription duration for musculoskeletal injury associated with the North Carolina Strengthen Opioid Misuse Prevention (STOP) Act.

To assess whether implementation of the Strengthen Opioid Misuse Prevention (STOP) Act was associated with an increase in the percentage of opioid prescriptions written for 7 days or fewer among patients with acute or postsurgical musculoskeletal conditions. An interrupted time-series study was conducted to determine the change in duration of opioid prescriptions associated with the STOP Act. Data were extracted from the electronic health record of a large health care system in North Carolina. Patients presenting from 2016 to 2020 with an acute musculoskeletal injury and the clinicians treating them were included in an interrupted time-series study (n = 12 839). Trends were assessed over time, including the change in trend associated with implementation of the STOP Act, for the percentage of prescriptions written for ≤7days. Among patients with acute musculoskeletal injury, less than 30% of prescriptions were written for ≤7days in January of 2016; by December of 2020, almost 90% of prescriptions were written for ≤7days. Prescriptions written for ≤7 days increased 17.7% after the STOP Act was implemented (P < .001), after adjustment for the existing trend. These results demonstrate significant potential for legislation to influence opioid prescribing behavior.

Evaluating the impact of alcohol minimum unit pricing on deaths and hospitalisations in Scotland: a controlled interrupted time series study

Since May 1, 2018, every alcoholic drink sold in Scotland has had minimum unit pricing (MUP) of £0·50 per unit. Previous studies have indicated that the introduction of this policy reduced alcohol sales by 3%. We aimed to assess whether this has led to reductions in alcohol-attributable deaths and hospitalisations. Study outcomes, wholly attributable to alcohol consumption, were defined using routinely collected data on deaths and hospitalisations. Controlled interrupted time series regression was used to assess the legislation's impact in Scotland, and any effect modification across demographic and socioeconomic deprivation groups. The pre-intervention time series ran from Jan 1, 2012, to April 30, 2018, and for 32 months after the policy was implemented (until Dec 31, 2020). Data from England, a part of the UK where the intervention was not implemented, were used to form a control group. MUP in Scotland was associated with a significant 13·4% reduction (95% CI -18·4 to -8·3; p=0·0004) in deaths wholly attributable to alcohol consumption. Hospitalisations wholly attributable to alcohol consumption decreased by 4·1% (-8·3 to 0·3; p=0·064). Effects were driven by significant improvements in chronic outcomes, particularly alcoholic liver disease. Furthermore, MUP legislation was associated with a reduction in deaths and hospitalisations wholly attributable to alcohol consumption in the four most socioeconomically deprived deciles in Scotland. The implementation of MUP legislation was associated with significant reductions in deaths, and reductions in hospitalisations, wholly attributable to alcohol consumption. The greatest improvements were in the four most socioeconomically deprived deciles, indicating that the policy is positively tackling deprivation-based inequalities in alcohol-attributable health harm. Scottish Government.

Evaluation of the effect of managing oxycodone/acetaminophen as a psychotropic medicine: An interrupted time-series study.

Background: Oxycodone/acetaminophen has been reported for misuse for many times in China. To cope with that, Chinese national authorities jointly issued a policy, requiring that oxycodone/acetaminophen should be managed as a psychotropic medicine starting 1 September 2019. This paper aimed to evaluate the effect of this policy in medical institutions. Methods: We used interrupted time-series analysis to examine the immediate level and slope changes in the mean number of tablets prescribed, proportion of oxycodone/acetaminophen prescription exceeding 30 pills, days supplied per prescription and the proportion of days supplied exceeding 10days with prescription data from 5 tertiary hospitals in Xi'an city between 1 January 2018 and 30 June 2021 (42months). We divided the prescriptions into two groups, one for long-term drug users, and the other for short-term drug users. Results: In total, 12,491 prescriptions were included in the final study, with 8,941 and 3,550 prescriptions for the short-term and long-term drug users, respectively. Significant differences in the proportion of prescriptions issued by various departments, were observed between pre- and post-implementation of the policy for both short-term and long-term drug users (p < 0.001). For short-term drug users, the policy implementation was only associated with an immediate level decrease in proportion of prescriptions exceeding 30 tablets (-4.09%, p < 0.001). For long-term drug users, after the policy, the mean number of tablets prescribed and the mean proportion of prescriptions exceeding 30 tablets experienced a level decrease of 22.96 tablets (p < 0.001) and a level decrease of 41.13% (p < 0.001), respectively; the mean number of days supplied showed a significant level decrease (6.88days per prescription) and slope increase (0.19days per month), and the mean proportion of days supplied exceeding 10days showed a significant level decrease (-10.51% per prescription) and a slope increase (0.27% per month). Conclusion: Implementation of stricter management for oxycodone/acetaminophen achieved its goal of reducing the risk of misuse in short-term drug users. For those long-term drug users, policy needed to be strengthened as the prescription exceeding 10days was still at a high level after the intervention. Policies targeting patients with different drug demands are needed. Many other strategies can be implemented, including establishing specific guidelines/principles and conducting training programs.

Evaluating the effectiveness of implementing a more severe law on prevention of road traffic injury mortality in mainland China: an interrupted time series study based on national mortality surveillance

BackgroundIn China, road traffic injury (RTI) is the seventh-leading cause of death More than 1.5 million adults in China live with permanent disabilities due to road traffic accidents. In 2011,...

Non-pharmaceutical interventions for COVID-19 reduced the incidence of infectious diseases: a controlled interrupted time-series study

BackgroundNon-pharmaceutical interventions (NPIs) have been implemented worldwide to suppress the spread of coronavirus disease 2019 (COVID-19). However, few studies have evaluated the effect of NPIs on other infectious diseases and none has assessed the avoided disease burden associated with NPIs. We aimed to assess the effect of NPIs on the incidence of infectious diseases during the COVID-19 pandemic in 2020 and evaluate the health economic benefits related to the reduction in the incidence of infectious diseases.MethodsData on 10 notifiable infectious diseases across China during 2010–2020 were extracted from the China Information System for Disease Control and Prevention. A two-stage controlled interrupted time-series design with a quasi-Poisson regression model was used to examine the impact of NPIs on the incidence of infectious diseases. The analysis was first performed at the provincial-level administrative divisions (PLADs) level in China, then the PLAD-specific estimates were pooled using a random-effect meta-analysis.ResultsA total of 61,393,737 cases of 10 infectious diseases were identified. The implementation of NPIs was associated with 5.13 million (95% confidence interval [CI] 3.45‒7.42) avoided cases and USD 1.77 billion (95% CI 1.18‒2.57) avoided hospital expenditures in 2020. There were 4.52 million (95% CI 3.00‒6.63) avoided cases for children and adolescents, corresponding to 88.2% of total avoided cases. The top leading cause of avoided burden attributable to NPIs was influenza [avoided percentage (AP): 89.3%; 95% CI 84.5‒92.6]. Socioeconomic status and population density were effect modifiers.ConclusionsNPIs for COVID-19 could effectively control the prevalence of infectious diseases, with patterns of risk varying by socioeconomic status. These findings have important implications for informing targeted strategies to prevent infectious diseases.

Interventions for improving adherence to iron chelation therapy in people with sickle cell disease or thalassaemia.

Interventions for improving adherence to iron chelation therapy in people with sickle cell disease or thalassaemia.

Suicide Deaths Before and During the COVID 19 Pandemic

IntroductionWith stressors that are often associated with suicide increasing during the coronavirus disease 2019 (COVID-19) pandemic, there has been concern that suicide mortality rates may also be increasing. Our objective was to determine whether suicide mortality rates increased during the COVID-19 pandemic.With stressors that are often associated with suicideincreasing during the coronavirus disease 2019 (COVID-19) pandemic,there has been concern that suicide mortality rates may alsobe increasing.ObjectivesOur objective was to determine whether suicidemortality rates increased during the COVID-19 pandemic.MethodsWe conducted an interrupted time-series study using data from January 2019 through December 2020 from 2 large integrated health care systems. The population at risk included all patients or individuals enrolled in a health plan at HealthPartners in Minnesota or Henry Ford Health in Michigan. The primary outcome was change in suicide mortality rates, expressed as annualized crude rates of suicide death per 100,000 people in 10 months following the start of the pandemic in March 2020 compared with the 14 months prior. We conducted an interrupted time-series study using data fromJanuary 2019 through December 2020 from 2 large integrated health care systems. The population at risk included all patients or individuals enrolledin a health plan at HealthPartners in Minnesota or Henry Ford HealthSystem in Michigan. The primary outcome was change in suicide mortality rates, expressed as annualized crude rates of suicide death per 100,000 people in 10 months following the start of the pandemic in March2020 compared with the 14 months prior.ResultsThere were 6,434,675 people at risk in the sample, with 55% women and a diverse sample across ages, race/ethnicity, and insurance type. From January 2019 through February 2020, there was a slow increase in the suicide mortality rate, with rates then decreasing by 0.45 per 100,000 people per month from March 2020 through December 2020 (SE= 0.19, P=0.03). There were 6,434,675 people at risk in the sample, with 55% women and a diverse sample across ages, race/ethnicity, and insurance type. From January 2019 through February 2020, there was a slow increase in the suicide mortality rate, with rates then decreasing by 0.45 per 100,000 people per month from March 2020 through December 2020 (SE= 0.19, P=0.03).ConclusionsOverall suicide mortality rates did not increase with the pandemic, and in fact slightly declined from March to December 2020. Our findings should be confirmed across other settings and, when available, using final adjudicated state mortality data. Overall suicide mortality rates did not increase with the pandemic, and in fact slightly declined from March to December 2020. Our findings should be confirmed across other settings and,when available, using final adjudicated state mortality data.Disclosure of InterestNone Declared

Interrupted time series segmented regression analysis for detecting waterborne disease outbreaks by syndromic surveillance.

Pathogens can enter the drinking water supply and cause gastroenteritis outbreaks. Such events can affect many people in a short time, making them a high risk for public health. In Australia, the Victoria State Government Department of Health is deploying a syndromic surveillance system for drinking water contamination events. We assessed the utility of segmented regression models for detecting such events and determined the number of excess presentations needed for such methods to signal a detection. The study involved an interrupted time series study of a past lapse in water treatment. The baseline period comprised the four weeks before the minimum incubation period of suspected pathogens, set at two days post-event. The surveillance period comprised the week after. We used segmented linear regression to compare the count of gastroenteritis presentations to public hospital emergency departments (EDs) between the surveillance and baseline periods. We then simulated events resulting in varying excess presentations. These were superimposed onto the ED data over fifty different dates across 2020. Using the same regression, we calculated the detection probability at p < 0.05 for each outbreak size. In the retrospective analysis, there was strong evidence for an increase in presentations shortly after the event. In the simulations, with no excess presentations (i.e., with the ED data as is) the models signalled 8% probability of detection. The models returned 50% probability of detection with 28 excess presentations and 100% probability of detection with 78 excess presentations. The transient increase in presentations after the event may be attributed to microbiological hazards or increased health-seeking behaviour following the issuing of boil water advisories. The simulations demonstrated the ability for segmented regressions to signal a detection, even without a large excess in presentations. The approach also demonstrated high specificity and should be considered for informing Victoria's syndromic surveillance system.

An Interrupted Time Series Analysis Measuring the Impact of Research and Education on Clinical Practice: Decreasing Allograft Use in Young Patients Using a Registry to Track Outcomes.

We sought to evaluate whether allograft utilization for primary anterior cruciate ligament reconstruction (ACLR) within our health-care system changed following the implementation of an allograft reduction intervention and whether revision rates within the health-care system changed following the initiation of the intervention. We conducted an interrupted time series study using data from Kaiser Permanente's ACL Reconstruction Registry. In our study, we identified 11,808 patients who were ≤21 years of age and underwent primary ACLR from January 1, 2007, through December 31, 2017. The pre-intervention period (15 quarters) was January 1, 2007, through September 30, 2010, and the post-intervention period (29 quarters) was October 1, 2010, through December 31, 2017. Poisson regression was used to evaluate trends over time in 2-year revision rates according to the quarter in which the primary ACLR was performed. Allograft utilization increased pre-intervention from 21.0% in 2007 Q1 to 24.8% in 2010 Q3. Utilization decreased post-intervention from 29.7% in 2010 Q4 to 2.4% in 2017 Q4. The quarterly 2-year revision rate increased from 3.0 to 7.4 revisions per 100 ACLRs pre-intervention and decreased to 4.1 revisions per 100 ACLRs by the end of the post-intervention period. Poisson regression found an increasing 2-year revision rate over time pre-intervention (rate ratio [RR], 1.03 [95% confidence interval (CI), 1.00 to 1.06] per quarter) and a decreasing rate over time post-intervention (RR, 0.96 [95% CI, 0.92 to 0.99]). In our health-care system, we saw a decrease in allograft utilization following the implementation of an allograft reduction program. During the same period, a decrease in the ACLR revision rate was observed. Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Education support services for improving school engagement and academic performance of children and adolescents with a chronic health condition.

Education support services for improving school engagement and academic performance of children and adolescents with a chronic health condition.

Ambulance Services Attendance for Mental Health and Overdose Before and During COVID-19 in Canada and the United Kingdom: Interrupted Time Series Study.

The COVID-19 pandemic impacted mental health and health care systems worldwide. This study examined the COVID-19 pandemic's impact on ambulance attendances for mental health and overdose, comparing similar regions in the United Kingdom and Canada that implemented different public health measures. An interrupted time series study of ambulance attendances was conducted for mental health and overdose in the United Kingdom (East Midlands region) and Canada (Hamilton and Niagara regions). Data were obtained from 182,497 ambulance attendance records for the study period of December 29, 2019, to August 1, 2020. Negative binomial regressions modeled the count of attendances per week per 100,000 population in the weeks leading up to the lockdown, the week the lockdown was initiated, and the weeks following the lockdown. Stratified analyses were conducted by sex and age. Ambulance attendances for mental health and overdose had very small week-over-week increases prior to lockdown (United Kingdom: incidence rate ratio [IRR] 1.002, 95% CI 1.002-1.003 for mental health). However, substantial changes were observed at the time of lockdown; while there was a statistically significant drop in the rate of overdose attendances in the study regions of both countries (United Kingdom: IRR 0.573, 95% CI 0.518-0.635 and Canada: IRR 0.743, 95% CI 0.602-0.917), the rate of mental health attendances increased in the UK region only (United Kingdom: IRR 1.125, 95% CI 1.031-1.227 and Canada: IRR 0.922, 95% CI 0.794-1.071). Different trends were observed based on sex and age categories within and between study regions. The observed changes in ambulance attendances for mental health and overdose at the time of lockdown differed between the UK and Canada study regions. These results may inform future pandemic planning and further research on the public health measures that may explain observed regional differences.