**2. Methods**

We did a secondary data analysis from a prospective, facility-based follow-up study, at all public regional referral hospitals in Dar-es- Salaam, Tanzania. Specifically, the study took place at Amana, Mwananyamala and Temeke regional referral hospitals. It was conceived as a clinical research study that assessed indications and outcomes of TAH in Dar es Salaam city, Tanzania. Dar-es-Salaam is a cosmopolitan city situated on the East-African coast. It is the business capital of Tanzania. The same city is projected to be 10th largest city on earth in population size come 2050. Geo-strategically, Dar-es-Salaam is a port city, and home to dozens of African demographic subsets, ranging from mainly the Bantu population group to African-Arabic mixed race population.

Data in the primary study was collected using a pre-designed clinical sheet that contained social, demographic, biological and clinical parameters on pre- and peri-480-hours post-hysterectomy. Specifically, HIV screening was accomplished using a serial algorithm involving SD Bioline HIV kit (SD Bioline HIV 1/2 3.0, Standard Diagnostics, Korea) to all participants. Those who were reactive on SD Bioline HIV test, confirmatory diagnosis was made using Unigold HIV kit (UniGold™HIV, Trinity Biotech Manufacturing Ltd, Bray-Ireland). Each participant was screened twice, first at the time of recruitment into the study, and again either before discharge from the ward post-operatively or anytime within 480-hours post-hysterectomy. Data collection started immediately upon a verbal informed consent for inclusion into the

primary study. Sample size was obtained using the prospective cohort formula from Kasiulevicius and others publication in the journal Gerontology back in 2006 [21];

$$\text{Sample size} = \frac{\left[Z\_a \sqrt{\left(1 + \frac{1}{m}\right) p^\*} \left(1 - p^\*\right) + Z\_\beta \sqrt{p\mathbf{1}}\right]^2}{\left(1 - p\mathbf{1}\right)/m + p\mathbf{2}\left(1 - p\mathbf{2}\right)}$$

*Zα* = Standard normal variate for level of significance.

*m* = Number of control subject per experimental subject.

*Zβ* = Standard normal variate for power or type 2 error as explained in earlier section.

*p*1 = Probability of events in control group.

*p*2 = Probability of events in experimental group p

$$P^\* = \frac{p2 + mp1}{m+1}$$

For values of Z = 1.96, α = 0.05, β = 0.8, m = 1.

Study population in the primary study included all women with a surrogate marker for *ageing process* (clinical indications necessitating total abdominal hysterectomy). Target population referred to all women who underwent *total abdominal hysterectomy* at any of Dar es Salaam Public Regional Referral Hospitals. Thus, for a participant to be eligible for recruitment into the study, she had to be planned for *total abdominal hysterectomy* and/or emergency total abdominal hysterectomy due to a decision made on the operation table (in-theatre major adverse events) out of another planned surgery at any of those facilities during the study time. All women who underwent sub-total hysterectomies were thus excluded. The decision to do so originated from the assumption that, *for a woman to be planned for total abdominal hysterectomy, the clinical decision rule must incorporate a pathology associated with what we characterized as an ageing process*. Participants were recruited upon official notification for total abdominal hysterectomy at clinics (outpatients) or wards (inpatients) after clinical indications. Participants were followedup to at most 480-hours post-operatively, or upon discharge from the ward post-operatively, whichever came first. Follow-up data included post-operative HIV serostata.

Data analysis was done using SAS software version 9.4 (SAS Institute, Cary-NC, USA). A minimum number of 106 women had at least 80% power of detecting a statistically significant difference at apriori 5% α-level. Continuous variables were summarised using median (with inter-quartile range). Categorical variables were summarized as proportion (with %). A generalised linear model was used to analyse data after appropriate validation of model assumptions. We considered at least 110 women as a rough estimate of effective sample size in cases of any potential refusal to participate/missing data. However, efforts were made to ensure minimal refusals to participate/missing information per participant via adoption of all surgical and nursing team members in the respective departments throughout the study period.

Ethical clearance for the primary study was obtained from ethical clearance committee at International Medical and Technological University (IMTU). Permission at referral facilities was sought from offices of municipal medical officers of health and facility in-charges of each hospital. Participants were approached with a verbal informed consent prior to recruitment into the primary study.
