Flexible assessment of trends in age-specific HIV incidence using two-dimensional penalized likelihood.
We present a method for estimating age- and time-specific HIV incidence using back-calculations of AIDS incidence data. Two-dimensional penalized likelihood is employed, using a flexible bivariate step function model of HIV incidence, together with a quadratic roughness penalty which leads to thin-plate spline smoothing. This allows incidence estimates to vary flexibly and smoothly in both age and time. We propose generalized cross-validation as a guide for choice of an appropriate level of smoothing and describe an EM algorithm for computing the estimates. We propose the method primarily for qualitative assessment of trends in age-specific incidence over time and apply it to a small Italian data set on men who have sex with men. The analysis suggests a trend over time of increasing relative incidence among younger individuals, consistent with incidence patterns observed in other countries.
Marschner
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IC
Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115, USA. marsch@sdac.harvard.edu
Bosch
R J
RJ
D000328:Adult; D000367:Age Factors; D000368:Aged; D015658:HIV Infections / Q000453:epidemiology*; D018451:Homosexuality, Male / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D016013:Likelihood Functions; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012306:Risk