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Sickness absence calculation


Sickness absence in NHSScotland can result in cancelled appointments and procedures and lead to increased expenditure on supplementary staff, such as medical locum and agency nurses. The sickness absence rate is a calculation which measures the percentage of hours lost due to sickness absence over a period of time.

The following applies for the data released as part of the NHSScotland Workforce official statistics publication.


Sickness absence data are sourced from SSTS via SWISS. Sickness absence includes absence types: normal sick leave, unpaid sick leave, industrial injury, accident involving a third party, and injury resulting from a crime of violence. A period of absence is recorded in SSTS with a start date, end date, absence type, absence reason, and hours lost.

The sickness absence rate is calculated by:

[sickness absence rate] = ( [working hours lost] / [total contracted hours] ) * 100

where [working hours lost] and [total contracted hours] are the sum of the individuals in group being considered (e.g. staff group) and are defined below. 

The absence rate available in the NHSScotland Workforce official statistics publication is calculated over a financial year. However, an absence rate can be calculated over other periods, such as a month.

Total contracted hours

The weekly contracted hours is adjusted to give the contracted hours over the calculation window

[total contracted hours] = [weekly contracted hours] * [52.179] * ( [number of months] / 12 )

where the factor 52.179 is used to standardise the number of weeks in a year (including a leap year every four years), and [number of months] are the number of months in the calculation window.

For example, to if a person is contracted to work for the standard 37.5 hours a week, then the total contracted hours for this person over a one month window is [total contracted hours] = 37.5 * 52.179 * (1 / 12) = 163.06.

If someone joins or leaves part way through the calculation window then only the hours that they worked used. 

Working hours lost

The number of [hours lost] is recorded in each line of absence in SSTS. This number will take into account different working patterns.

[working hours lost] = ([days lost in window] / [total days lost]) * [hours lost]

where [days lost in window] / [total days lost] is the proportion of days that the absence falls within the calculation window. 

On occasion the [hours lost] value has been input with excessive zeros (e.g. 2000 instead of 200). To minimise the impact this has on the calculations, if the [hours lost] is greater than 200, but the length of the absence is less than 32 days then [hours lost] is adjusted to the maximum number of hours lost over one month (52.179 * 37.5 / 12 )