Our primary goal was to determine whether factors believed to affect motivation and opportunity in pandemic fatigue8 influenced adherence to physical distancing during a period of widespread containment measures. On six occasions, we ascertained non-work, non-household contacts for the previous week among our two cohorts and modeled changes in different types of contact rates as affected by sociodemographic characteristics. We estimated several interactions between sociodemographic factors and week in the association with type-specific contact rates.
Of 997 participants in C1 and 339 in C2 who completed the baseline survey, 972 (97.5%) and 305 (90.0%), respectively, provided sufficient sociodemographic information for inclusion in the analysis. Not all participants completed all follow-up surveys, yielding 4,198 contacts in C1 and 1,684 in C2 for analysis. Contacts with unrealistic values were removed, for final totals of 4,189 and 1,681, respectively.
The age of C1 participants ranged from 25 to 74 years (mean 40.6, SD 6.5), and the cohort included 859 women, 106 men, and 4 individuals identifying as non-binary (Table 1). In C2, participants ranged from 52 to 89 years (mean 68.0, SD 7.2), and the cohort included 154 women and 151 men. Demographic representativeness relative to the Minnesota and Iowa populations has been reported elsewhere.16
Table 1
Sociodemographic profile of the study cohorts
Sociodemographic Characteristic
|
Cohort 1: Adults with Children
(n = 972)
|
Cohort 2: Adults Over 50
(n = 305)
|
Age (years)
|
|
40.6 (SD = 6.5)
|
68.0 (SD = 7.2)
|
Gender Identity
|
Men
|
106 (10.9%)
|
151 (49.5%)
|
|
Women
|
862 (88.7%)
|
154 (50.5%)
|
|
Non-binary
|
4 (0.4%)
|
0
|
Racial/Ethnic Identity a
|
American Indian or Alaska Native
|
20 (2.1%)
|
2 (0.7%)
|
|
Asian
|
27 (2.8%)
|
0
|
|
Black or African-American
|
11 (1.1%)
|
0
|
|
Hispanic, Latinx, or Spanish Origin
|
15 (1.5%)
|
1 (0.3%)
|
|
Middle Eastern or North African
|
3 (0.3%)
|
0
|
|
Native Hawaiian or Other Pacific Islander
|
1 (0.1%)
|
0
|
|
White
|
935 (96.2%)
|
280 (91.8%)
|
|
Another race, ethnicity, or origin
|
8 (0.8%)
|
3 (1.0%)
|
|
Not indicated
|
0
|
21 (6.9%)
|
Education Level
|
Up to high school degree/GED
|
38 (3.9%)
|
7 (2.3%)
|
|
Trade school/2-year degree or some college
|
131 (13.5%)
|
73 (23.9%)
|
|
Four-year degree
|
385 (39.6%)
|
119 (39.0%)
|
|
Master’s/doctorate/professional degree
|
418 (43.1%)
|
106 (34.8%)
|
Income
|
< $60,000
|
129 (13.3%)
|
71 (23.3%)
|
|
$60,000 to < $80,000
|
135 (13.9%)
|
40 (13.1%)
|
|
≥ $80,000
|
708 (72.8%)
|
194 (63.6%)
|
Employment Status
|
Full time
|
688 (70.8%)
|
59 (19.3%)
|
|
Part time
|
143 (14.7%)
|
29 (9.5%)
|
|
Not employed
|
141 (14.5%)
|
217 (71.1%)
|
Own Transportation
|
No
|
10 (1.0%)
|
26 (8.5%)
|
|
Yes
|
962 (99.0%)
|
279 (91.5%)
|
Household Member with Underlying Health Conditions
|
No
|
588 (60.5%)
|
101 (33.1%)
|
|
Yes
|
384 (39.5%)
|
204 (68.9%)
|
People in Household (n)
|
|
4.2 (SD = 1.1)
|
2.3 (SD = 2.0)
|
State
|
Iowa
|
350 (36.0%)
|
N/A
|
|
Minnesota
|
622 (64.0%)
|
305 (100%)
|
Parkinson’s Status
|
No
|
N/A
|
206 (67.5%)
|
|
Yes
|
N/A
|
99 (32.5%)
|
a Racial/ethnic totals add to > 100%, because participants could select more than one category. |
Abbreviations: GED, general educational development test; SD, standard deviation |
Average weekly contacts varied over time, by contact type, and by cohort
In both cohorts, retail contacts produced the greatest number of average contacts per week over the study period (Fig. 1). The rate of all contact types increased during the middle of the study period and decreased toward the end. Outdoor contacts in C1 appeared to increase more sharply than any other type during the middle of the study period, which coincided with the summer months.
We modeled statistically significant non-linear changes over time in the rate of contacts for all contact types in both cohorts (column 1 in Figs. 2 and 3), except for ‘other’ contacts. Significant non-linear changes in contact rates were all modeled with a positive linear term and negative second-degree polynomial term for week. For example, the coefficients for the per-week change in retail contacts in C2 were 0.376 for the linear term and − 0.007 for the squared term (Table S1).
However, while almost all models estimated the lowest contact rate in week 16 (the week beginning April 13, 2020), the first week of data collection, the timing of peak contact rates differed between the two cohorts. For an average individual in C1, all contact types were predicted to peak between weeks 30 (July 20) and 32 (August 3) based on our final models. The number of peak weekly contacts predicted for an average C1 participant ranged from 2.1 for dining contacts to 9.1 for retail contacts (Table S2). Predicted contact rate peaks in C2 occurred for retail and outdoor contacts in week 28 (July 6), followed by visitors and residential contacts in weeks 29 and 30, respectively. Predicted dining contacts peaked in week 32, and ‘other’ contacts did not peak until week 39 (September 22). C2 predicted peak contact rates were lower for every contact type compared to C1, ranging from 1.0 predicted dining contact per week to 7.1 predicted retail contacts per week for an average C2 participant during peak weeks. These findings show that the older adult cohort returned to non-work, non-household contacts across a range of settings in a more staggered pattern and at a lower level than the family cohort.
Factors associated with changes in the rates of visitors and residential contacts differed
We examined the sociodemographic characteristics interacting with week for each contact type to understand which factors motivate more rapid declines in adherence in different settings, as expressed as higher contact rates. Visitors to participants’ homes and contacts during participants’ visits to the homes of others (‘residential contacts’) both occur in the same setting, but changes over time in these contact rates were associated with different factors. At baseline when there were substantial shutdowns, C1 participants without a personal vehicle had more visitors (Table S3), but the rate of visitors increased faster among vehicle owners (ratio of RRs 1.04; 95% CI 1.00, 1.08), with higher predicted rates in that group by the end of the study (row 1 in Fig. 2). In C2, every 10-year increase in age was associated with a 1% increase in visitors RRweek (ratio of RRs 1.01; 95% CI 1.00, 1.02) (row 1 in Fig. 3). The visit rate among individuals in this cohort from racially or ethnically marginalized groups was significantly lower at baseline than among white participants (main term RR 0.03; 95% CI 0.00, 0.19) and increased over time, with the change in visit rate per week 11% higher than among white participants (ratio of RRs 1.11; 95% CI 1.07, 1.16).
Conversely, for residential contacts in C2, there were no initial racial/ethnic differences, but white participants had a larger weekly increase in the residential contact rate relative to racially/ethnically marginalized individuals (row 2 in Fig. 3), though this became non-significant in the final model (Table S4). The only other factor influencing the change in rate of residential contacts in this cohort was household size, with each additional person in the household reducing the residential contact RRweek by 1% (ratio of RRs 0.99; 95% CI 0.99, 1.00). The effect of household size was opposite in C1, with each additional person increasing the residential contact RRweek by 1% (ratio of RRs 1.01; 95% CI 1.00, 1.02) (row 2 in Fig. 2). Individuals with some college or a four-year degree had higher baseline residential contact rates than those with up to a high school degree (Table S4). With each additional week of the pandemic, their residential contact rates both decreased 5% relative to individuals with up to a high school degree (ratios of RRs 0.95; 95% CIs 0.91, 1.00 and 0.91, 0.99, respectively), till the average contact rate of individuals with up to a high school degree became higher than either other group at approximately week 30. Overall, these results indicate that although visitor and residential contacts arise from interactions in the same setting, changes over time in their frequency are likely motivated by different factors.
Changes in outdoor contact rates varied with education level
Similar to the effect of education on residential contacts in C1, outdoor contact rates were initially lower among participants with up to a high school education and then increased 1–5% more quickly than among the other groups (Table S5), again exceeding the others’ estimated contacts at approximately week 30 (row 3 in Fig. 2). Age also had a small effect on outdoor contacts in this cohort, with each 10-year increase in age associated with a 1% decrease in the RRweek (ratio of RRs 0.99; 95% CI 0.97, 1.00). The education effect observed in C1 was also seen in C2, with individuals with up to a high school education having proportionally much lower outdoor contact rates initially, increasing 8–11% more quickly than the other groups (Table S5). However, on average, individuals with up to a high school education did not exceed the outdoor contact rate of the other groups by the end of the study period in this cohort (row 3 in Fig. 3). The observed dynamics of individuals with up to a high school degree across cohorts suggests there may be a common effect of education level on outdoor contact rates.
Demographic characteristics were the only factors associated with differences in changes in retail contact rates
Individuals in C1 identifying as non-binary had fewer retail contacts at baseline than those identifying as men (Table S6). However, our model indicated the one-week relative change in retail contact rate was 9% greater for non-binary individuals compared to men (ratio of RRs 1.09; 95% 1.04, 1.14), exceeding those of both men and women by the end of the study period (row 4 in Fig. 2). In C2, the weekly change in retail contacts was 3% greater for racially/ethnically marginalized individuals than for white individuals (ratio of RRs 1.03; 95% 1.00, 1.06) (row 4 in Fig. 3). No other variables emerged as significant modifiers of the rate of change of retail contacts in either cohort.
Dining and ‘other’ contact rate changes differed across several characteristics
The cohorts differed markedly in the characteristics that modified changes in dining and ‘other’ contact rates, which encompass the most discretionary non-work, non-household contacts we examined. The dining contact RRweek increased 14–15% faster among C1 participants with up to a high school education compared to the other education level groups (row 5 in Fig. 2; Table S7), similar to what was seen with residential and outdoor contacts. It decreased by 2% (ratio of RRs 0.98; 95% 0.95, 1.00) for each 10-year increase in age. In C2, women’s dining contact rate was significantly lower than that of men’s (Table S7); however, neither the interactions with gender nor vehicle ownership were significant in the final model, though either effect would have been small due to the low average dining contacts in this cohort (row 5 in Fig. 3). While changes in ‘other’ type contacts over time were minimal, individuals in C1 with a household member with a condition that would predispose them to severe COVID-19 outcomes (row 6 in Fig. 2) and individuals in C2 reporting a household income <$60,000 (row 6 in Fig. 3) experienced greater increases in this contact type relative to other groups (Table S8). Taken together, the results for dining and ‘other’ contacts demonstrate that a wide variety of factors may be driving changes in these particularly discretionary contact types.
Sensitivity analysis
Comparing histograms of reported counts of outings and contacts with inferred counts from the censored Poisson for participants reporting ≥ 4 outings or ≥ 5 contacts, outdoor outings stood out as the only count that was markedly underrepresented by the inferred counts (Figures S1, S2). In repeating our analysis using only inferred counts for all surveys, the effect of week was lower to varying degrees in C1 for all contact types and in C2 for retail and outdoor contacts. However, interaction terms changed only marginally, if at all. The ‘other’ contact type was an exception to this, with significant changes in interaction terms.