Julianne Moore has been accumulating accolades for her performance as a linguistics professor afflicted with early-onset Alzheimer’s in “Still Alice,” and rightfully so. One of the great actresses of our day, she captures the heartbreak of the woman’s decline with a degree of nuance and subtlety that makes one wish that the adaptation of Lisa Genova’s novel by Richard Glatzer and Wash Westmoreland were entirely worthy of her. Certainly the film is sensitive and obviously sincere. But it’s also decorous to a fault when it should be devastating, underplaying the effects of the disease in much the same fashion that TV movies-of-the-week often do with such stories while nonetheless succumbing to their clichés.

Alice Howland (Moore), an internationally respected authority in her field, is on the faculty of Columbia University, where her husband John (Alec Baldwin) is a research physician. Theirs is frankly a privileged life. They have a beautifully appointed apartment and a beach house as well, and they’ve raised—and sent into the world—three fine children. While the youngest of them, Lydia (Kristen Stewart), is a bit of a concern, embracing a tenuous career as a would-be actress, the others, Anna (Kate Bosworth) and Tom (Hunter Parrish), seem successful and happy. Otherwise, all appears in good order.

But Alice begins to suffer memory lapses—getting lost in the middle of a lecture, finding herself unable to find the right word in a conference presentation—but dismisses them as trivial. It’s only when she gets lost during her customary campus jog, unable to recall where she is, that she becomes sufficiently worried to consult a doctor, who gives her tests—at first simple word problems, then diagnostic examinations—that reveal that she has Alzheimer’s which, we learn along with her, advances more rapidly when it begins so early, especially if the victim is highly educated. To make matters even worse, the disease is identified as genetic—her dead father, an alcoholic who died young, probably had it, and her children have a 50% chance of inheriting it.

The impact on all the Howlands could hardly be greater, but in this telling they all handle the revelation of Alice’s condition with a degree of equanimity that’s rather remarkable. Even the children, when informed of the fact that they might be carriers of the disease, are at most nonplussed. To be sure, there’s a taste of acidity to Baldwin’s performance: John reacts with stiffness when he talks with Alice’s physician, and later as her condition deteriorates his interest in his own professional advancement sometimes takes precedence over his commitment to what might be best for her. And while Moore captures, through small, carefully calibrated gestures, the gradual but all too swift progress of the disease—while avoiding a blatant appeal for audience sympathy even as Alice prepares a computer message to herself about possibly committing suicide—one senses a desire on the writer-directors’ part not to get overly explicit about the physical toll the condition is taking on the character, a fear that going too far in that respect might make viewers uncomfortable.

That reticence is preferable, of course, to emotional overkill; one has to be grateful that the film doesn’t become as cloying and grossly manipulative as many disease-of-the-week movies have been. (It might also spring, at least to some extent, from the fact that Glatzer suffers from Lou Gehring’s Disease, an ailment that affects the body rather than the mind but is equally debilitating.) But it does saddle “Still Alice” with a sense of genteel decorum—evinced also in Denis Lenoir’s smooth cinematography and Tammaso Ortino’s elegant production design, as well as Susan Perlman’s sets—that’s somewhat at odds with the awfulness of the subject. In that respect it resembles Sarah Polley’s “Away from Her,” another film about mental deterioration that avoids mawkishness but in doing so comes across as more intellectually than emotionally compelling. Even when it aims for the heartstrings—in Ilan Eshkeri’s mournful score, or the use of home movies to refer back to Alice’s earlier life—“Still Alice” comes across, oddly enough, as halfhearted.

And yet there’s much to admire, not least Moore’s remarkable performance, which—even more than Julie Christie’s in “Away from Her”—catches the pain of loss in the character with startling immediacy. One senses that had the filmmakers asked her to, she could have given us still more; but one should be grateful for what she does bring to the part. The prickliness that Baldwin invests John with is also memorable, and while not entirely effacing memories of her pallid turns in the “Twilight” series, Stewart exhibits some real spirit as the Howland child who proves most willing to sacrifice to help her mother, and most touched by the experience she shares with her.

Paradoxically even when pulling its emotional punches “Still Alice” can’t entirely escape the limitations of the disease-of-the-week genre, but largely as a result of Moore’s extraordinary skill it largely transcends them.