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

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

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

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

Interviewer household visit Nurse visit

Nurse visit

Interviewer visit Nurse visit Nurse visit

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

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) †

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) †

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)

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 † (0.25-0.37) 0.81 (0.64-1.02) 0.40 † (0.36-0.43) 0.89 * (0.79-0.99) Weekend 0.46 † (0.37-0.57) 0.86 (0.65-1.12) 0.51 † (0.45-0.57) 0.97 (0.84-1.24)

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 (0.94-1.13) 0.96 (0.85-1.07) 1.92 † (1.77-2.08) 1.17 ** (1.06-1.30) Weekend 1.12 (0.99-1.25) 1.09 (0.94-1.25) 1.31 † (1.18-1.46) 0.86 (0.79-1.02)

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)

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

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

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

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.