NACCHO received 2,300 questionnaires (80 percent response rate), of which 2,296 had answers to at least 1 of the 21 preparedness items that were selected for our analysis. Missing values were on average <1 percent per item. The factor analysis confirmed the hypothesized structure. A three-factor solution, accounting for 48 percent of the total variance, was interpreted as meaningful. Therefore, the association between independent variables and PHEP outcomes was investigated using summary variables in addition to single items.
Population data were available for 2,292 LHDs, ranging from 313 to 9,998,371 residents, with a mean of 130,838 (SD 426,592) and a median of 34,273. Population size was consistently and significantly related to preparedness activities and capacities (). For 20 out of 21 items, a significant difference (chi test, p<.01) was found in the proportions of LHDs able to perform activities across communities grouped by population size. The proportion increased with the size of the population served by the LHD, with large differences between the most and least populous communities. Most dramatically, 60.5 percent of the LHDs serving the largest communities (>200,000 residents) reported having a PIS, compared with 3.2 percent in the smallest communities (<25,000).
Preparedness by Population Size, Presence of a Board of Health, and Participation in Coalitions—All Selected Preparedness Items
The same pattern was found when data were analyzed using summary scales ( and ). For the four scales, the ratio between the largest and the smallest communities ranged from more than 20:1 for EP-Staff to approximately 3:2 for EP-Activities. Similar results were obtained when summary variables were treated as continuous variables either using factor scores or the simple sum of items (all β coefficients were positive with p values <.05).
Preparedness by Population Size, Presence of a Board of Health, and Participation in Coalitions—Composite Scales
Figure 1 Percentage of Local Health Departments Achieving the Following Outcomes by Population Size: EP-Staff: Two Positive Responses for Two Items; EP-Capacities: Three Positive Responses for Five Items; EP-Activities: Four Positive Responses for Five Items; (more ...)
Board of Health
Information about the presence of a BOH was available for 2,293 LHDs; of these 1,707 (74.4 percent) had a BOH. The relationship between having a BOH and PHEP outcomes was significant for 6 out of 21 EP-Activities, but for 2 of these 6 activities it worked in a direction opposite to what was expected: having a BOH was negatively associated with the LHD's ability to employ a PIS and perform EMS activities. Having a BOH was positively associated with better outcomes for several activities, namely review of legal authorities, writing or updating of an emergency plan, conducting drills and exercises, and training. A similar pattern was found using summary scales: 9.4 percent of LHDs with a BOH had both a PIS and EPC compared with 15.7 percent of those without a BOH, whereas 73.3 percent of LHDs with a BOH achieved the EP-Activities outcome compared with 61.5 percent LHDs without a BOH (p≤.0001).
These relationships suggest an interaction between population size and the presence of a BOH, which led us to explore their joint relationship with PHEP outcomes using a logistic regression model for each of the four summary variables. In this analysis, population size was a negative confounder for EP-Capacities and EP-Performance and a positive confounder for EP-Staff and EP-Activities. After adjusting for population size, having a BOH had a positive effect on all summary variables; however, the effect was statistically significant only for the EP-Activities scale. LHDs with a BOH had 1.86 times greater odds of being able to perform four out of five EP-Activities (odds ratio=1.86, 95 percent confidence interval 1.48, 2.36) (). Similar results were obtained using EP-Activities as a continuous variable (sum of items) in the linear regression model adjusting for population size (β=0.14, p value <.05). This result was consistent but not significant when the outcome variable was the factor score.
The question about participation in organizing coalitions was asked only of the 519 agencies completing module three. Among the respondents (423), 275 (65 percent) reported having worked in such activity. For 18 of 21 items considered and for two of the four summary variables (EP-Activities, EP-Performance, and EP-Capacities was just short of significance), LHDs that worked to organize coalitions were better prepared than those who did not (p<.05). Seeing the impact of population size on the effect of having a BOH, we tested whether population size was a confounder of the relationship between having participated in coalitions and PHEP outcomes, but the effect was not substantially changed ( and ). Similar results were found when the summary variables were tested as continuous variables with better outcomes for LHDs with experience in creating coalitions (all β coefficients were positive with p values <.05). Results were not significant when using the factor score as outcome variable for EP-Staff, again likely because of a loss of power.