It is known that high blood pressure in one’s 50s puts a person at risk for dementia in later life. What about in younger people? In the October 31 Neurology, scientists led by Rachel Whitmer of the Kaiser Permanente Division of Research, Oakland, California, report that hypertension in the 30s and 40s has a similar effect, but only in women. Same-age men with hypertension developed dementia at the same rate as their normotensive peers, according to the data. The findings come as a surprise, since many prior epidemiological studies concluded that midlife high blood pressure increased everyone’s risk of getting dementia. Whitmer and colleagues caution that their finding could result from a survival effect, meaning that some men with hypertension may have died before follow-up could have detected incident dementia.
- Midlife high blood pressure increased risk for dementia in women.
- A survival effect could obscure an effect in men.
“Our findings emphasize how important it is to look at the timing of risk factors,” said first author Paula Gilsanz.
Prior work has established high blood pressure in late middle age—usually the 50s—as a risk factor for developing late-life dementia in both men and women (Whitmer et al., 2005; Kimm et al., 2011; Apr 2017 news). Whitmer and colleagues wondered if hypertension in younger people might have the same effect.
To find out, Gilsanz and colleagues reviewed the medical records of 5,646 members of the Kaiser Permanente Northern California integrated health care delivery system. Each had voluntarily seen a doctor for a routine checkup between 1964 and 1973, when they were 30–35 years old, and filled out a health survey. Between 1978 and 1985, when they were over 40, they had a second checkup. Both times doctors tested for hypertension, defined as a systolic blood pressure at or above 140 mm Hg or a diastolic blood pressure of 90 mm Hg or more. The researchers then checked records from 1996–2015 to see who had been diagnosed with dementia.
In total, 532 people had been—298 women and 234 men. Though midlife hypertension was more common in the men, it didn’t appear to increase their chances of developing dementia. In the women, by contrast, hypertension in their 30s or 40s carried 63 and 73 more risk, respectively, of being diagnosed with dementia compared with their normotensive peers.
The results suggest that hypertension in early to midlife poses a dementia risk for women, not men, wrote the authors. This could be explained by a greater risk for organ damage and cardiovascular disease from hypertension that has been reported for women (Palatini et al., 2011; Cheng et al., 2014).
However, the authors caution that more men in their sample died before follow-up. Having hypertension might have contributed to their early deaths, hence a link between hypertension and dementia in men could have gone undetected. The authors also note that screening and treatment for high blood pressure has evolved considerably since the 1960s, which might limit the generalizability of these findings.
Lewis Kuller, University of Pittsburgh, noted that using hospital records may have underestimated dementia in men while overestimating it in women, since women are hospitalized more frequently, raising the chances that dementia would be detected. In addition, since most men die younger than women do, and there is a delay between diagnosis of dementia and its inclusion in records, the diagnosis may have gone unrecorded in some men. While Kuller considered these the most likely reasons for the reported sex difference, he noted that hormone replacement therapy in this cohort may also have increased women’s risk for hypertension and dementia (see full comment below).—Gwyneth Dickey Zakaib
- Whitmer RA, Sidney S, Selby J, Johnston SC, Yaffe K. Midlife cardiovascular risk factors and risk of dementia in late life. Neurology. 2005 Jan 25;64(2):277-81. PubMed.
- Kimm H, Lee PH, Shin YJ, Park KS, Jo J, Lee Y, Kang HC, Jee SH. Mid-life and late-life vascular risk factors and dementia in Korean men and women. Arch Gerontol Geriatr. 2011 May-Jun;52(3):e117-22. PubMed.
- Palatini P, Mos L, Santonastaso M, Saladini F, Benetti E, Mormino P, Bortolazzi A, Cozzio S. Premenopausal women have increased risk of hypertensive target organ damage compared with men of similar age. J Womens Health (Larchmt). 2011 Aug;20(8):1175-81. Epub 2011 Jun 24 PubMed.
- Cheng S, Claggett B, Correia AW, Shah AM, Gupta DK, Skali H, Ni H, Rosamond WD, Heiss G, Folsom AR, Coresh J, Solomon SD. Temporal trends in the population attributable risk for cardiovascular disease: the Atherosclerosis Risk in Communities Study. Circulation. 2014 Sep 2;130(10):820-8. Epub 2014 Aug 11 PubMed.
- Launer LJ, Ross GW, Petrovitch H, Masaki K, Foley D, White LR, Havlik RJ. Midlife blood pressure and dementia: the Honolulu-Asia aging study. Neurobiol Aging. 2000 Jan-Feb;21(1):49-55. PubMed.
- Alonso A, Mosley TH Jr, Gottesman RF, Catellier D, Sharrett AR, Coresh J. Risk of dementia hospitalisation associated with cardiovascular risk factors in midlife and older age: the Atherosclerosis Risk in Communities (ARIC) study. J Neurol Neurosurg Psychiatry. 2009 Nov;80(11):1194-201. Epub 2009 Aug 19 PubMed.
- Gilsanz P, Mayeda ER, Glymour MM, Quesenberry CP, Mungas DM, DeCarli C, Dean A, Whitmer RA. Female sex, early-onset hypertension, and risk of dementia. Neurology. 2017 Oct 4; PubMed.