HPV re-activation in older women: an increased cancer risk unrelated to sexual behaviour?

Older women who have had ≥5 lifetime sexual partners could turn out to be a relatively high-risk group for Human Papilloma Virus (HPV) and associated cervical lesions – regardless of declining sexual activity.  If – that is – Gravitt, Viscidi et al. (http://jid.oxfordjournals.org/content/207/2/272.full.pdf+html?sid=4bc8141c-9b7c-4a13-8a43-451d6fa85fcf; http://jid.oxfordjournals.org/content/207/2/211.full.pdf+html?sid=4bc8141c-9b7c-4a13-8a43-451d6fa85fcf) are correct to see the results of their cohort study of Baltimore women attending obstetric-gynaecology clinic as supportive of the hypothesis that the HPV experienced by these older high-risk women is a reactivated form of the infection.  The virus, they suggest, may remain undetectable in the body for years in order to emerge in later years with immune-senescence – like the varicella zoster virus that reactivates as shingles.  This would explain the double peak in age-specific HPV prevalence (debut and menopause) in some cultures; while the absence of this pattern in the US and N. Europe, they hypothesize, may be an effect of the more restrictive sexual mores of the pre-sixties generation.

What is the evidence?  When the results are stratified according to number of lifetime sexual partners, it is discovered that the Population Attributable Risk (PAR) of high-risk (HR) variants of HPV (i.e. those causing cancerous lesions) due to ≥5 lifetime partners is 87% among the older study participants, and 28% among the younger ones; while the PAR of HR-HPV due to a new sex partner is 7.7% among the older group and 28% among the younger.  This, as the authors argue, is consistent with reactivation of the virus in later life, though they admit reactivation is difficult to prove.

If this hypothesis is supported by further research, it will certainly impact on a number of issues that have been a concern for our readers and contributors.  First, the question of women’s perceived risk of cervical cancer – important because it has been shown to predict cancer screening attendance and has been associated with HPV vaccination uptake (http://sti.bmj.com/content/88/6/400.abstract?sid=2f5a46a3-43d9-4648-a3f6-9f1a46384f61, pp.1-2).  If Gravitt et al. are right, then currently less sexually active older women, who are nevertheless in the higher-risk group on account of past sexual activity, are in serious danger of underestimating their risk; furthermore, that risk could, in reality, be greater that we imagined owing to the behavioural impact of the sexual revolution.  Second, the question of stigmatization, especially in relation to HPV testing at routine “smear” tests (http://sti.bmj.com/content/82/2/169.abstract?sid=2f5a46a3-43d9-4648-a3f6-9f1a46384f61).  If HPV is often present, but undetected, and, when detected, may turn out to have no relation to current sexual activity, then the stigmatizing link between HPV status and current sexual behaviour is, at least, weakened – which ought to have a de-stigmatizing effect.  Third, HPV vaccination, and the concern of certain parents that it might lead to sexual disinhibition (http://sti.bmj.com/content/87/4/349.abstract?sid=44f0f0a6-c872-4cb1-9ca1-afa0aa8db872).  Here, again, the idea that sexually inactive, or less active, people can be at serious risk runs counter to the public perception of a direct link between current sexual behaviour and cervical cancer risk – which ought to make HPV vaccination easier to justify to a public concerned about sexual disinhibition.