Improving the quality of adult mortality data collected in demographic surveys: validation study of a new siblings' survival questionnaire in Niakhar, Senegal

Abstract

Background: In countries with limited vital registration, adult mortality is frequently estimated using siblings' survival histories (SSHs) collected during Demographic and Health Surveys (DHS). These data are affected by reporting errors. We developed a new SSH questionnaire, the siblings' survival calendar (SSC). It incorporates supplementary interviewing techniques to limit omissions of siblings and uses an event history calendar to improve reports of dates and ages. We hypothesized that the SSC would improve the quality of adult mortality data.

Methods and findings: We conducted a retrospective validation study among the population of the Niakhar Health and Demographic Surveillance System in Senegal. We randomly assigned men and women aged 15-59 y to an interview with either the DHS questionnaire or the SSC. We compared SSHs collected in each group to prospective data on adult mortality collected in Niakhar. The SSC reduced respondents' tendency to round reports of dates and ages to the nearest multiple of five or ten ("heaping"). The SSC also had higher sensitivity in recording adult female deaths: among respondents whose sister(s) had died at an adult age in the past 15 y, 89.6% reported an adult female death during SSC interviews versus 75.6% in DHS interviews (p = 0.027). The specificity of the SSC was similar to that of the DHS questionnaire, i.e., it did not increase the number of false reports of deaths. However, the SSC did not improve the reporting of adult deaths among the brothers of respondents. Study limitations include sample selectivity, limited external validity, and multiple testing.

Conclusions: The SSC has the potential to collect more accurate SSHs than the questionnaire used in DHS. Further research is needed to assess the effects of the SSC on estimates of adult mortality rates. Additional validation studies should be conducted in different social and epidemiological settings.

Trial registration: Controlled-Trials.com ISRCTN06849961

Figure 1. Flow diagram of the enrollment process.

Figure 2. Map of the study site.

Location of study participants in Senegal. Black triangles represent interviewed respondents, and white circles represent sampled individuals who did not participate in the validation study, either because they refused, were absent, or could not be traced. RCT, randomized controlled trial.

Figure 3. Age/date heaping in siblings' survival histories, by study group.

(A) Current age of live siblings; (B) age of sibling at death; (C) date of sibling death. The time series represented here are heaping ratios calculated as indicated in Equation 1. In (B), we did not include data on deaths at ages 40 y and above because of limited sample size. Deaths at ages 40 y and above are, however, included in (C).

Figure 4. Effects of the SSC on bias in the proportion of respondents who report having had at least one death among their adult siblings.

The true proportion of respondents with one or more deaths among their adult sisters or brothers was calculated using the values of sensitivity and specificity in Table 2, along with the formula for indicated in Equation 2 (derived in [50]).

Figure 5. Subgroup analyses of the effects of the SSC on the sensitivity of SSH data for adult female deaths.

The analytical sample for the analyses is constituted of respondents with at least one adult death among their sisters according to the HDSS dataset. The circles in the graphs represent odds ratios of reporting an adult female death associated with use of the SSC questionnaire among respondents in these sibships. Error bars represent 95% confidence intervals. Confidence intervals are clipped at 20. Estimates of odds ratios are obtained from stratified Mantel-Haenszel odds ratios. We tested for homogeneity of odds ratios across all strata of the classifying variable. The thick line represents estimates of the odds ratios for the full sample of the validation study. The dashed line corresponds to an odds ratio equal to 1. *p<0.1, tests of significance refer to the test of the homogeneity of the odds ratio across strata of the classifying variable.

Figure 6. Subgroup analyses of the effects of the SSC on the sensitivity of SSH data for adult male deaths.

The analytical sample for the analyses is constituted of respondents with at least one adult death among their brothers according to the HDSS dataset. The circles in the graphs represent odds ratios of reporting an adult male death associated with use of the SSC questionnaire. Error bars represent 95% confidence intervals. Estimates of odds ratios are obtained from stratified Mantel-Haenszel odds ratios. We tested for homogeneity of odds ratios across all strata of the classifying variable. The thick line represents estimates of the odds ratios for the full sample of the validation study. The dashed line corresponds to an odds ratio equal to 1. **p<0.05, tests of significance refer to the test of the homogeneity of the odds ratio across strata of the classifying variable.

Figure 7. Distribution of interviewing time by study group and week of fieldwork.

In this figure, the bottom and top of each box represents the first and third quartiles of the distribution of interviewing time, and the middle line represents the median. The whiskers represent the most extreme values within 1.5 times the interquartile range; circles represent outliers. Two interviews reported to have lasted 472 and 625 min are excluded from these figures for visualization purposes, but were included in calculations of median time. These interviews lasted exceptionally long because they were discontinued and the interviewer subsequently left the respondent's house at the time of interruption. The interviewer later returned to finish the interview, but did not record the time at which they discontinued the interview, nor did they record the time at which they resumed it. As a result, the actual interviewing time is not known. Five interviews reported to have lasted more than 100 min are included in this graph. These interviews were also momentarily interrupted, but the interviewer remained at the respondent's house until completing the interview. Data on interview duration were missing for 45 interviews. Of these, 24 were in the DHS group (3.9%) and 21 were in the SSC group (3.7%).