Abstract
Background: To explore the association between blood pressure and cognition in older participants in the Shanghai Aging Study.Methods: Data were drawn from 3,327 participants at the baseline of Shanghai Aging Study. History of hypertension was inquired and confirmed from participants' medical records. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured by research nurses in the early morning. Participants were diagnosed with “cognitive normal,” “mild cognitive impairment (MCI),” or “dementia” by neurologists using DSM-IV and Petersen criteria. Multivariate logistic regression was used to evaluate the association between history of hypertension, duration of hypertension, SBP, DBP, or classification of blood pressure and cognitive function. Generalized linear model was used to assess the relation between duration of hypertension, SBP, or DBP and Mini Mental State Examination (MMSE).Results: A significantly higher proportion of hypertension [78 (76.5%)] was found in participants with dementia than in those with MCI [347 (59.3%)] and cognitive normal [1,350 (51.1%)] (P < 0.0001). Participants with dementia had significantly higher SBP [157.6 (26.1) mmHg] than those with MCI [149.0 (23.7) mmHg] and cognitive normal [143.7 (22.6) mmHg] (P < 0.0001). After adjusting for sex, age, education, living alone, body mass index, anxiety, depression, heart disease, diabetes, and stroke, the likelihood of having dementia was positively associated with history of hypertension (OR = 2.10; 95% CI: 1.22, 3.61), duration of hypertension (OR = 1.02 per increment year; 95% CI: 1.01, 1.04), higher SBP (OR = 1.14 per increment of 10 mmHg; 95% CI: 1.04, 1.25), higher DBP (OR = 1.22 per increment of 10 mmHg; 95% CI: 1.02, 1.45), moderate hypertension (OR = 2.09; 95% CI: 1.10, 3.99), or severe hypertension (OR = 2.45; 95% CI: 1.20, 4.99). The MMSE score was inversely correlated to duration of hypertension (β = −0.0088 per increment year; 95% CI: −0.0158, −0.0018, P = 0.0132), SBP (β = −0.0655 per increment of 10 mmHg; 95% CI: −0.1022, −0.0288, P = 0.0005), and DBP (β = −0.1230 per increment of 10 mmHg; 95% CI: −0.1915, −0.0545, P = 0.0004).Conclusion: Our results suggest that hypertension and high blood pressure may be potential risk factors for dementia. Blood pressure management for the elderly may be important for maintaining cognitive vitality.
Highlights
Cognitive impairment has a great impact on disability and mortality among the elderly, while it reduces the quality of life for both patients and their caregivers
Some epidemiological studies showed that hypertension is an important risk factor of dementia [8, 9], which was evident from the positive relationship between blood pressure at midlife and the subsequently higher risk of cognitive impairment or dementia late in life [10,11,12]; some other studies provided contradictory evidence that low blood pressure was a risk factor for dementia and cognitive decline [13,14,15]
After adjusting for age, sex, education, body mass index (BMI), living alone, anxiety, depression, heart disease, diabetes, and stroke, the likelihood of having dementia was positively associated with history of hypertension (OR = 2.10; 95% confidence interval (CI): 1.22, 3.61), duration of hypertension (OR = 1.02 per increment year; 95% CI: 1.01,1.04), higher systolic blood pressure (SBP) (OR = 1.14 per increment of 10 mmHg; 95% CI: 1.04, 1.25), higher diastolic blood pressure (DBP) (OR = 1.22 per increment of 10 mmHg; 95% CI: 1.02, 1.45), moderate hypertension (OR = 2.09; 95% CI: 1.10, 3.99), or severe hypertension (OR = 2.45; 95% CI: 1.20, 4.99), but it was not associated with mild hypertension (OR = 1.31; 95% CI: 0.70, 2.45)
Summary
Cognitive impairment has a great impact on disability and mortality among the elderly, while it reduces the quality of life for both patients and their caregivers. Hypertension is a highly prevalent condition, occurring in one-third of the world’s adults and in two-thirds of adults over 65 years of age [3, 4]. Both hypertension and dementia are age-related comorbidities which may induce considerable disabilities [1, 5,6,7]. Some epidemiological studies showed that hypertension is an important risk factor of dementia [8, 9], which was evident from the positive relationship between blood pressure at midlife and the subsequently higher risk of cognitive impairment or dementia late in life [10,11,12]; some other studies provided contradictory evidence that low blood pressure was a risk factor for dementia and cognitive decline [13,14,15].
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