Table 1 Summary of proposed age-related mechanisms
From: Explaining age disparities in tuberculosis burden in Taiwan: a modelling study
Mechanisms | Descriptions | Notation | Prior distribution | Parameters | |
|---|---|---|---|---|---|
Definition (unit) | |||||
m0 | Base model | No additional age-related mechanisms are incorporated. | βbase | 0.001–30 | Infection rate (per year) |
m1 | Immune senescence | The risk of developing TB disease following recent or remote infection increases with age, potentially related to comorbidities and health-related behaviours. | σ(C) | 0.1–1 | Multiplier to baseline progression rates for children, compared to adults |
σ(E) | 1–10 | Multiplier to baseline progression rates for elders, compared to adults | |||
m2 | Declining transmissiona | Frequent Mtb transmission in the past generated a substantial number of latently infected population, who become the elderly cases in the present day. A rapid decline of Mtb transmission happens recently because of improved living standard and health service. | βini | 0.001–30 | Infection rate prior to t0 (per year) |
βend | 0.001–30 | Infection rate at 2017 (per year) | |||
t0 | 1957–2005 | Beginning year of transmission decline | |||
m3 | Age-specific assortativity | Mixing between age groups lead to different infection tendencies, as a result of social activity and infectiousness. Elders are additionally restricted to mix with younger age groups in order to retain the high burden in the population. | w(A) | 0.2–5 | Connectivity weight of adults for mixing with others, compared to children |
w(E) | 0.2–5 | Connectivity weight of elders for mixing with others, compared to children | |||
ε | 0.01–1 | Isolation factor for mixing between elders and younger age groups | |||