[{"@context":"https:\/\/schema.org\/","@type":"Article","@id":"https:\/\/betterbones.com\/bone-health-basics\/infamous-t-score-neglected-z-score\/#Article","mainEntityOfPage":"https:\/\/betterbones.com\/bone-health-basics\/infamous-t-score-neglected-z-score\/","headline":"The infamous T score and neglected Z score","name":"The infamous T score and neglected Z score","description":"Print PDF eBook Facebook Twitter Gmail LinkedIn Pinterest Table of Contents Toggle Unraveling the mysteries of bone density test resultsPutting the T score in perspectiveThe overlooked Z score Unraveling the mysteries of bone density test results I bet most of the Better Bones community have heard of the infamous bone density T score. But I […]","datePublished":"2018-05-16","dateModified":"2026-04-28","author":{"@type":"Person","@id":"https:\/\/betterbones.com\/author\/brownbetterbonesgmail-com\/#Person","name":"Dr. Susan E. Brown, PhD","url":"https:\/\/betterbones.com\/author\/brownbetterbonesgmail-com\/","identifier":72,"image":{"@type":"ImageObject","@id":"https:\/\/secure.gravatar.com\/avatar\/8e08d87bd45250c6616e1752933a6576aba077f335d97ee337a0cde5e435cbd3?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/8e08d87bd45250c6616e1752933a6576aba077f335d97ee337a0cde5e435cbd3?s=96&d=mm&r=g","height":96,"width":96}},"publisher":{"@type":"Organization","name":"Center for Better Bones","logo":{"@type":"ImageObject","@id":"https:\/\/betterbones.com\/wp-content\/uploads\/2018\/12\/Better-Bones-AMP.png","url":"https:\/\/betterbones.com\/wp-content\/uploads\/2018\/12\/Better-Bones-AMP.png","width":150,"height":60}},"image":{"@type":"ImageObject","@id":"https:\/\/betterbones.com\/wp-content\/uploads\/2018\/05\/image-1.jpeg","url":"https:\/\/betterbones.com\/wp-content\/uploads\/2018\/05\/image-1.jpeg","height":1109,"width":2120},"url":"https:\/\/betterbones.com\/bone-health-basics\/infamous-t-score-neglected-z-score\/","about":["Bone Health Basics"],"wordCount":684,"keywords":["osteopenia","bone density","t score","z score"],"articleBody":" Print PDF eBook\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tFacebook\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tTwitter\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tGmail\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tLinkedIn\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tPinterest\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tTable of ContentsToggleUnraveling the mysteries of bone density test resultsPutting the T score in perspectiveThe overlooked Z scoreUnraveling the mysteries of bone density test resultsI bet most of the Better Bones community have heard of the infamous bone density T score. But I suspect that few understand what the T score means, and even fewer know about the hidden value of the Z score. Contrary to popular (mis)understanding, the T score does not measure fracture risk or indicate that you need bone drugs. \u00a0So what then does the T score indicate?Putting the T score in perspectiveThe T score measures how closely your bone density compares to that of an average 30-year-old of the same sex. This comparison is expressed in terms of the \u201cstandard deviation,\u201d or SD, which you may recognize from a statistics class as being the amount that represents the typical distance above or below the mean for individual measurements. So, if your bone density differs from the average 30-year-old\u2019s (which it probably will!), that difference will be characterized as \u201c\u20131.5\u201d if your bones are 1.5 SD below the mean, or \u201c+1.2\u201d if they\u2019re 1.2 SD above the mean.\u2028\u2028As the chart shows, a T score of \u20131.0 is described as osteopenia, and \u20132.5 is described as osteoporosis \u2014 even though bone density bears little relationship to fracture risk (but that\u2019s <a href = \u201chttps:\/\/betterbones.com\/testing\/bone-density-tests-arent-enough\/\u201d>another story<\/a>).The T score measures how closely your bone density compares to that of an average 30-year-old of the same sex. This comparison is expressed in terms of the \u201cstandard deviation,\u201d or SD, which you may recognize from a statistics class as being the amount that represents the typical distance above or below the mean for individual measurements. So, if your bone density differs from the average 30-year-old\u2019s (which it probably will!), that difference will be characterized as \u201c\u20131.5\u201d if your bones are 1.5 SD below the mean, or \u201c+1.2\u201d if they\u2019re 1.2 SD above the mean.As the chart above shows, a T score of \u20131.0 is described as osteopenia, and \u20132.5 is described as osteoporosis \u2014 even though bone density bears little relationship to fracture risk (but that\u2019s another story).In this second chart (below), 68%, or around two-thirds, of the population falls within 1 SD of the mean, either lower or higher than the average, and another 32% (the remaining third) of the population falls more than 1 SD beyond the mean. Keep in mind that, starting in her mid-30s, the average woman will lose 35% of her cortical bone mass and 50% of her trabecular bone mass over her lifetime (assuming she doesn\u2019t take steps to limit bone loss). So it is totally reasonable to expect that an older woman is not going to have the bone density of a 30-year-old woman, and that her T score will be a negative rather than a positive number.The overlooked Z scoreElsewhere in your testing results, you will find out your Z score. The Z score compares an individual to others their own age and sex \u2014 which makes it a much more realistic assessment of how your bones are faring in their lifelong journey. Where an active, healthy 80-year-old woman, compared to a 30-year-old, might have a T score of \u20132.0, when compared to other 80-year-old women, she could very well have a Z score of +1.0 or even +2.0! It\u2019s a pity that the Z score, which \u201ccompares apples to apples,\u201d gets so much less attention than the T score. It hardly seems realistic to be worried about having lower bone density that a 30-year-old \u2014 but there\u2019s good reason to pay attention when your bone density is much lower than people your own age. For instance, if your Z score is \u20132.0 or more, it means that very few people your age have a bone density that low, and it signals the need for a complete medical workup looking for all possible cause of excessive bone loss.Reference:Hunter, D, and Sambrook, PN. Bone loss: Epidemiology of bone loss. Arthritis Res. 2000:2(6):441-445."},{"@context":"https:\/\/schema.org\/","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Bone Health Basics","item":"https:\/\/betterbones.com\/bone-health-basics\/#breadcrumbitem"},{"@type":"ListItem","position":2,"name":"The infamous T score and neglected Z score","item":"https:\/\/betterbones.com\/bone-health-basics\/infamous-t-score-neglected-z-score\/#breadcrumbitem"}]}]