Table 2

Definition of terms (continued)

 Terms Definitions Zw Penetrance of MS for the subset of susceptible women (F, G) within (Z) during (ET)– Also called the ‘failure-probability’ for susceptible women during (ET). Zm Penetrance of MS for the subset of susceptible men (M, G) within (Z) during (ET)– Also called the ‘failure-probability’ for susceptible men during (ET). c, d Limiting values (constants) for the ‘failure- probability’ in susceptible men (c); and susceptible women (d)—that is, (Zm≤c≤1) and (Zw≤d≤1).c=limit of (Zm) as: (a→∞) & d=limit of (Zw) as: (a→∞). p Proportion of women in the (G) subset—that is, p=P(F│G). (E) Event that a randomly-selected member of (G)—the proband—experiences an environment ‘sufficient’ to cause MS in them. P(E│G, ET) Probability that the event (E) occurs during (ET) for a proband randomly-selected from (G). u Variable, which represents the environmental exposure-level as measured by the odds that the event (E) occurs during any (ET). a Environmental exposure-level during some specific (ET)—that is, when: (u=a). h(u), k(u) Unknown (and unspecified) hazard functions for susceptible men—h(u); and for susceptible women—k(u). H(a), K(a) Cumulative hazard functions for susceptible men – H(a); and for susceptible women – K(a)—defined as the definite integrals of these unknown and unspecified hazard functions from an exposure-level of (u=0) to an exposure-level of (u=a). R>0 Value of the proportionality factor (if the hazards are proportional)—that is, k(u) = R * h(u). Rapp The ‘apparent’ value of R—that is, the value of R for proportional hazards whenever: (c=d≤1). λw, λm Environmental exposure thresholds for developing MS in susceptible women (λw) and susceptible men (λm) (see Methods: Longitudinal models: General considerations). λ Difference in the environmental exposure threshold between susceptible women and susceptible men: that is, λ = λw – λm.
• MS, multiple sclerosis.