1. The right time for a survey
Jennifer Mindell, Laia Bécares, Maria Aresu UCL
Hanna Tolonen THL, Helskinki, Finland
ESRA 19th July 2013

2. Introduction Falling response rates internationally
Concerns over representativeness
New interest in HESs across Europe
Many planning to invite participants to examination centre
Most only in working hours 2

3. Methods (1) HSE 2006 Descriptive analyses by demographic and ses
Combined time & day categories
Weekday during the day (Mon-Fri before 5.00pm)
Weekday evening (Mon-Thurs 5.00pm onwards)
Weekend (Friday 5.00pm until Sunday evening)
Uni- and multi-variable regression using demographic and socio-economic variables to build best model

4. Methods (2) Multivariable regression of exemplar health-related variables
Self-reported health, Limiting longstanding illness
Lifestyle behaviours
Smoking, Alcohol
Measurements
BMI, Obesity, Waist circumference, Systolic BP
Biological samples
Total cholesterol, Glycated haemoglobin

5. Interviewer household visit
Nurse visit

6. Nurse visit

7. Interviewer visit
Nurse visit
Nurse visit

8. Multivariable regression
Time / day of visit was significantly related to:
Sex
Age
Marital status
Economic activity
Equivalised household income
Area deprivation
Ethnicity

9. Multivariable regression model (1)
Time and day of Interview
*p<0.05, **p<0.01, †p<0.001
Monday-Thursday 17:00 onwards
Friday 17:00 onwards and weekend
RRR (95% CI)
Age (per year)
0.98 (0.97;0.98) †
0.99 (0.98;0.99) †
Sex: Female (male)
0.80 (0.73;0.88) †
0.82 (0.73;0.92) **
Economic activity (employed)
ILO unemployment
0.58 (0.46;0.73) †
0.54 (0.40;0.73) †
Retired
0.26 (0.22;0.31) †
0.30 (0.24;0.37) †
Other
0.42 (0.37;0.49) †
0.55 (0.46;0.65) †

10. Multivariable regression model (2)
Time and day of Interview
*p<0.05, **p<0.01, †p<0.001
Monday-Thursday 17:00 onwards
Friday 17:00 onwards and weekend
RRR (95% CI)
Marital Status (single)
Married or civil partnership
 1.21 (1.04;1.39) *
0.92 (0.77;1.10)  
Separated or divorced
1.03 (0.83; 1.26)
0.87 (0.68; 1.12)
Widowed
1.27 (0.95; 1.69)
1.15 (0.83; 1.62)
Cohabiting
1.16 (0.98;1.39)
0.86 (0.69;1.07)
Equivalised household income tertile (lowest)
Middle tertile
1.62 (1.41;1.85) †
1.50 (1.26;1.77) †
Highest tertile
2.30 (2.04;2.59) †
2.16 (1.86;2.50) †

11. Multivariable regression model (3)
Time and day of Interview
**p<0.01, †p<0.001
Monday-Thursday 17:00 onwards
Friday 17:00 onwards and weekend
RRR (95% CI)
Ethnicity (White)
Asian or Asian British
1.44 (1.13;1.85) **
3.29 (2.58;4.22) †
Black or Black British
1.57 (1.12;2.20) **
2.97 (2.10;4.20) †
Other
0.91 (0.62;1.32)
2.28 (1.58;3.30) †
Area Deprivation (least deprived tertile) 
Middle tertile
1.06 (0.94;1.19)
1.31 (1.13;1.52) †
Most deprived tertile
0.84 (0.75;0.94) **
1.05 (0.92;1.21)

12. Poor self-rated health Limiting longstanding illness
General health
*p<0.05, **p<0.01, †p<0.001
Poor self-rated health
Limiting longstanding illness
Unadjusted
Fully adjusted
O.R.
(95% C.I.)
Weekday daytime 1
Weekday evening
0.30 †
( )
0.81
( )
0.40 †
( )
0.89 *
( )
Weekend
0.46 †
( )
0.86
( )
0.51 †
( )
0.97
( )

13. Current cigarette smoker
Risk behaviours
*p<0.05, **p<0.01, †p<0.001
Current cigarette smoker
Exceeded recommended alcohol intake
Unadjusted
Fully adjusted
O.R.
(95% C.I.)
Weekday daytime 1
Weekday evening
1.03
( )
0.96
( )
1.92 †
( )
1.17 **
( )
Weekend
1.12
( )
1.09
( )
1.31 †
( )
0.86
( )

14. Systolic blood pressure (mmHg)
Measurements
*p<0.05, **p<0.01, †p<0.001
BMI
(kg/m2)
Waist circumference
(cm)
Systolic blood pressure (mmHg)
Unadjusted
Fully adjusted
Coeff
(S.E.)
Weekday daytime
Weekday evening
-0.37 **
(0.11)
0.23
(0.12)
-1.54 **
(0.47)
0.21
(0.53)
-7.87 †
(1.1)
-0.26
(1.3)
Weekend
-0.57 †
(0.14)
-0.04
(0.15)
-0.21
(0.65)
-8.30 †
(1.4)
-2.44
(1.6)

15. Blood analytes 0.06 (0.07) -0.01 (0.08) -0.07 -0.04 0.13 (0.09) (0.10)
Total Cholesterol
(mmol/L)
Glycated haemoglobin
(%)
Unadjusted
Fully adjusted
Coeff
(S.E.)
Weekday daytime
Weekday evening
0.06
(0.07)
-0.01
(0.08)
-0.07
-0.04
Weekend
0.13
(0.09)
(0.10)
0.17

16. Conclusions
Marked demographic and socio-economic differences in the time of day and day of week of interview and nurse data collection in HSE.
These affect results for self-reported health, health behaviour, & physical measurements.
Variations by time & day in health variables disappear or reduce when adjusted for demographic and socio-economic variables

17. Implications When planning or conducting a general population survey:
consider how their survey could be organised to optimise representative participation
When using the results of surveys:
check whether there may be bias in the results

18. Acknowledgements Interviewers and nurses, for data collection
HSE participants
Colleagues at NatCen for providing data and helpful comments
Read more:
Mindell J, Aresu M, Bécares L, Tolonen H. Representativeness of participants in a cross-sectional health survey by time of day and day of week of data collection. Eur J Public Health. 2012;22:364-9.