Official Statistics

Methodology: near to real-time suspected suicide surveillance (nRTSSS) for England

Updated 28 November 2024

Applies to England

Purpose

This supplement supports the use and understanding of the nRTSSS monthly trend report which is currently published as official statistics in development (previously known as experimental statistics). This publication is a new statistic, and during the development phase it will be tested with users, in line with the standards of trustworthiness, quality, and value in the Code of Practice for Statistics.

This supplement includes:

• details of the data set used to produce these statistics

• approach used to calculate monthly suspected suicide rates

• approach used to calculate quarterly proportions of suspected suicides by method type group

• summary of strengths and limitations

Publishing as official statistics in development aims to ensure transparency about the developmental phase, how the statistics will be improved to enhance its quality (including accuracy and reliability) and value for users.

All analytical and statistical approaches used in this report have been consulted on and endorsed by experts in epidemiology and prevention of suicide. This includes academics, clinicians, service providers and commissioners, and local RTSSS systems, public health teams and police force areas (PFAs).

Data source and reporting

This analysis and reporting draw upon data from across England supplied by local police forces submitting to National Police Chiefs’ Council (NPCC) Suicide Prevention Portfolio. It is provided by NPCC to the Office for Health Improvement and Disparities (OHID) on a monthly basis, 6 weeks after month’s end. There is an ambition to reduce both the police and OHID processing time and produce the report in less than 12 weeks after month’s end.

Although data is collected at PFA level, statistics are reported at England level only to comply with:

• code of practice for statistics

• data ethics framework

• Samaritans’ media guidelines for reporting suicide and online resources

This is because analyses will be reported as monthly rates or quarterly proportions where publication at sub-national level might not be appropriate within the above standards and guidelines.

The term ‘suspected suicide’ is used throughout the report, because in the data received from NPCC cause of death and the listed methods have not yet been confirmed by coroner inquest and therefore should be viewed as provisional. All police forces contributing to nRTSSS use a standard definition of ‘suspected suicide’ and operate to the same data collection guidance. This guidance includes data collection templates and an explanation of how each data variable is defined and collected. For these purposes, a ‘suspected suicide’ is a sudden and unexpected death where it appears from the initial police assessment of the circumstances that:

• a deliberate self inflicted act has resulted in death

• there are underlying indicators of intentional self harm

• it was a fatal injury or poisoning of undetermined intent, there is no evidence of any third party involvement and there are substantial accompanying indicators of a probable ‘suspected suicide’ - a list of factors and circumstances indicating a probable ‘suspected suicide’ is available to the attending officer conducting the assessment and collecting the data

The data presented in this report is for rapid surveillance. It is intended to complement but not replace Office for National Statistics (ONS) reporting of suicide, which is the most complete and accurate data available.

Reporting format

These official statistic in development will be published as a monthly statistical report and data tables. It will include monthly rates of deaths by suspected suicides (overall, by sex and age groups) and quarterly proportions (overall only) by method type group. Data will cover the latest 15 months or 5 quarters available.        

All reporting will be for deaths by suspected suicide in people aged 10 years and over. This approach aligns with reporting of suicide statistics by ONS.

Any counts where suspected suicides are 5 or below will be supressed from all reporting and this will include secondary suppression as required. To minimise the risk of disclosure by differencing, monthly rates for persons are a total of males and females due to monthly counts for other gender being 5 or lower. This has no or minimal impact on the rates compared to inclusion of all genders. This approach is in line with disclosure rules used for reporting from other public health or health datasets.

Data quality and coverage

The following fields from the data collected by NPCC are used for the purpose of analysis and reporting, and are considered to be of high or good data quality:

• age

• gender

• date of death

• place of death

• method

Recording of gender other than female and male, indicates differences in recording practices and standards across local PFAs and will be subject to data quality improvement activities. Therefore, only female and male are currently used and will be referred as ‘sex’ in accordance with the ONS style guide.  

Use of further data fields will be part of ongoing data quality improvement activities and will be included in reporting once assessed as of sufficient quality.  

There are 39 police forces in England and all now submit data to the NPCC Suicide Prevention Portfolio. However, historical data is not available for all PFAs and at times delays in submission may mean that data cannot be included in reporting for the latest month. Therefore, more recent data is likely to be less complete and might be subject to change. All late submissions will be included in analysis once received and historical data will be updated within the next publication.  

Due to low counts of suspected suicides for City of London Police, for analytical purposes this data is combined with Metropolitan Police Service, resulting in 38 reporting areas.

Data completeness assessment

Data submitted for each PFA is compared to expected figures based on an average of equivalent months in the most recent 3 years of registered ONS suicide data based on date of death. At least 2 years lag is included for ONS suicide data to allow for delays in registrations.

For this analysis suspected suicide cases are allocated to a PFA based on where the event occurred rather than the attending police force or the place of residence for the deceased. Suspected suicide data is pooled over 12 months period ending in the latest reporting month. For example, for data up to October 2023:

• deaths by suspected suicide between November 2022 and October 2023 are used

• comparable data on registered ONS suicides is based on an average for the periods November 2018 and October 2019, November 2019 and October 2020 and November 2020 and October 2021

Crude rates are produced for suspected and registered suicides for each PFA using the appropriate or latest available mid-year estimate (MYE) populations based on the 2021 Census. For example, for registered suicides for the periods November 2018 to October 2019, November 2019 to October 2020, and November 2020 to October 2021, MYE populations for 2018, 2019 and 2020 are used, whereas 2022 MYE populations are used for suspected suicides between November 2022 and October 2023.     

Incidence rate ratios (IRRs) are calculated by dividing rates of deaths for suspected suicides by registered suicides (by date of occurrence). Local PFAs with IRRs 0.85 or higher are included in the monthly reporting as there are likely to be more suspected than registered suicides. This approach allows for exclusion of PFAs with evidence of underreporting - IRRs cut off point below 1 is used to allow for some random variation in deaths by suspected suicide (especially for smaller PFAs) and any impact of potential decreasing trends. For PFAs where additional deaths are reported later than 6 weeks after month’s end, IRRs will be recalculated.

These exclusion criteria are used for the purpose of calculating population based statistics only, as sensitivity analysis indicated that inclusion of PFAs below the expected level may result in underestimating of monthly suspected suicide rates. In this report this applies to monthly rates only. Where proportions of suspected suicides are reported (for example for method type), all received data is included.

Monthly rates

Monthly rates are calculated as age directly standardised rates (DSRs) using 2013 European standard population as the reference population. Date of death and place of death occurrence are used to allocate deaths to the relevant month and English PFAs. The appropriate or latest available MYE populations based on the 2021 Census are used to calculate DSRs. For example, 2022 MYE populations are used for suspected suicides between November 2022 and October 2023.    

As this reporting is made available for rapid surveillance, monthly rates are calculated using the latest available MYE populations at the time of monthly rates publication. This means that the following MYE population estimates are used:

• 2022 MYE populations for the calculation of monthly rates up to May 2024 (published August 2024)
• 2023 MYE populations for the calculation of monthly rates for June 2024 (published September 2024) and onwards

Sensitivity analysis carried out indicates that recalculation of monthly rates once more up-to-date MYE populations are available has a minimal impact on the rates.

For each monthly rate, PFAs contribute to the England value if:

• the police force submitted local data other than cases reported by British Transport Police

• the IRR is 0.85 or above

If the above criteria are not met, any British Transport Police cases and MYE populations for the PFAs not meeting the standards are excluded from the calculation of monthly DSRs for England. If further deaths are reported later than 6 weeks after month’s end for the excluded PFAs and the above standards are met, DSRs for England will be recalculated and updated at next feasible publication.

Using DSRs enables meaningful comparison of rates over time and across groups (for example, females and males). Using direct standardisation means that rates presented are not the rate for the population that the cases were drawn from but what the rate would have been if those cases were in a standardised population. As the populations that the deaths are reported from are likely to change from month to month, using DSRs means that the comparison between those months is valid because it has been translated to the standard population.

As rates of death by suicide and suspected suicide vary across the country, while this surveillance is not yet based on all of England, figures will be affected by which PFAs are included. To provide additional information of how PFAs inclusion and exclusion is likely to impact on monthly rates of suspected suicides, DSRs of deaths by suicide for the most recent 5 years are used for each PFA using place of death occurrence. Using an average rank of DSRs across 5 years, PFAs are allocated to 3 equal groups as low, medium or high DSRs.

Quarterly proportions

When data is presented as proportions of cases rather than population based statistics, all received death records are included. This ensures that important information on, for example, changes in method type is presented using the highest number of deaths available for analysis.      

Proportions of suicides by method type are presented as quarterly proportions.

Calendar quarters are used as:

• quarter 1 for January to March

• quarter 2 for April to June

• quarter 3 for July to September

• quarter 4 for October to December

Quarterly proportions are added to the reporting once a full quarter of data is available. Historical deaths submitted late by local police forces are included in the next feasible publication.

As the method type recorded is a provisional indication for the cause of death before confirmed by coroner inquest, some cases have more than one method recorded. Where multiple methods are reported they contribute to each method type group. Therefore, some cases will be counted more than once, resulting in higher totals than the count of deaths.    

Methods reported by the local police forces are mapped to broader method type groups based the on ONS approach for reporting. Where method is reported as unknown this is grouped with ‘other’. The method type groups are:

• drowning

• fall and fracture

• poisoning

• hanging, suffocation and strangulation

• jumping or lying in front of a moving object

• sharp object

• other or unknown

From January 2024 reporting, for some cases where method is indicated as unknown or other during the initial police assessment, information within the free text field has been used to allocate a method to one of the above groups. This change has been applied to all retrospective data periods.

Strengths and limitations

The strengths of nRTSSS are:

1. The monthly reporting acts as an early warning system for indications of change in suicides through analysis of data on suspected suicides. Statistics on registered deaths by suicide at a national level are provided by ONS and it can take up to 2 years for the official ONS data to come through.
2. Reporting using nRTSSS means that rather than waiting up to 2 years to analyse trends, analysis can be carried out much earlier and generally within 3 months from the death occurring.
3. As completeness of data on sex and age is of high quality, monthly rates are presented by those demographic sub-groups allowing for a more targeted identification of changing trends.
4. Availability of data on method type allows for early identification of areas for suicide prevention.
5. As all PFAs submit to NPCC data collection, national coverage means that the reporting is based on a high number of deaths allowing for meaningful interpretation of the data and detection of true changes rather than based on random variation.
6. Monthly updates for the reporting allow for inclusion of delayed submissions increasing robustness of the statistics. Even where submissions are delayed, reporting remains more timely compared to data for registered suicides.

The limitations of nRTSSS are:

1. Data for some PFAs is below what would be expected and therefore is not included in the reporting of monthly rates.
2. Some deaths are submitted later than 6 weeks after month’s end. Therefore, more recent data should be used with a higher level of caution and it will be subject to change once further deaths are received.
3. Currently only demographic breakdown by sex and age groups is included. Reporting for other populations at higher risk of suicide is currently not feasible due to lower data quality and it will be subject to data quality improvement. For example, this may include breakdown by ethnicity or deprivation.
4. Although reporting at England level ensures sufficient numbers for monthly reporting, sub-national analysis is of value to support local action. Where data on deaths by suspected suicides is collected locally, this remains the best source of information for local action. Reporting of sub-national analysis based on nRTSSS data will be subject to future engagement and development in relation to geographies and time periods to cover.
5. Cluster (geographical and non-geographical) analyses are currently not included in the reporting. Such analyses require further changes to the format of the data received and methodological approach development.