Table 2

Definition of terms (continued)

TermsDefinitions
Zw Penetrance of MS for the subset of susceptible women (F, G) within (Z) during (E T)
– Also called the ‘failure-probability’ for susceptible women during (E T).
Zm Penetrance of MS for the subset of susceptible men (M, G) within (Z) during (E T)
– Also called the ‘failure-probability’ for susceptible men during (E T).
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, E T)Probability that the event (E) occurs during (E T) 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 (E T).
a Environmental exposure-level during some specific (E T)—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 menH(a); and for susceptible womenK(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>0Value of the proportionality factor (if the hazards are proportional)
—that is, k(u) = R * h(u).
R app The ‘apparent’ value of R—that is, the value of R for proportional hazards whenever: ( c=d1).
λ w , λ m Environmental exposure thresholds for developing MS in susceptible women (λ w) and susceptible men (λ m) (see Methods: Longitudinal models: General considerations).
λ Difference in the environmental exposure threshold between susceptible women and susceptible men: that is, λ = λ w – λ m .
  • MS, multiple sclerosis.