The mutual caregiving lower blood pressure and heart rate

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Spouses in older marriages are increasingly taking on the role of their partner’s caregiver in dealing with chronic conditions like heart disease, memory loss, and cancer.

In a growing number of instances, both spouses care for each other as they struggle with any one of a variety of health issues such as arthritis, diabetes, and respiratory problems.

In a Yale School of Public Health study published this week in Health Psychology, researchers investigated how both giving and receiving support affects husbands’ and wives’ blood pressure and emotions when both partners are dealing with health conditions.

The researchers expected that mutual caregiving would lower blood pressure and heart rate for both individuals and that wives would likely reap more benefit from the support than husbands.

The actual findings were surprising.

The study’s primary author, Yale School of Public Health (YSPH) Associate Professor Joan Monin, explains:

“What we found was that when husband’s received support from their wives, the husband’s blood pressure and distress decreased,” said Monin, who examines caregiver relationships as a researcher with the YSPH Social and Behavioral Sciences Department.

“When wives received similar support, husbands and wives felt closer, but both partners’ heart rate remained elevated and wives felt even more distressed.”

So why did wives benefit less from caregiving support from their spouse?

Monin suspects everyday social interactions and traditional gender roles may be at play.

The researchers note in the study that husbands may expect and feel less stressed when they receive support from their wives because they are used to receiving such support in their everyday lives.

Wives, on the other hand, may not expect their husbands to engage in such support and are not used to or uncomfortable with receiving it.

Indeed, in the study, husbands said they expected more emotional support for the chronic conditions in everyday life than wives did.

The findings are important because they offer new insight into why gender differences exist when it comes to the health benefits of marriage.

Previous research has established that husbands receive more health benefits from marriage than wives do, as evidenced by studies showing husbands tend to die sooner than wives after the death of their spouse.

Studies have also shown that wives are more responsible for maintaining an emotionally healthy marriage and that both men and women count on female family members for their needs more than male family members.

While wives may benefit less from spousal caregiving than husbands, support for wives is important for strengthening intimacy and helping wives regulate distress caused by their husband’s illness, the researchers said.

Most caregiving studies focus on the health implications of one spouse caring for another.

This study is believed to be the first applying controlled rigorous scientific analysis of gender differences in older marriages in which both spouses care for each other as they deal with their own health concerns.

The study encompassed 98 older married couples, who were asked to answer a questionnaire about their current health conditions and their relationship with their spouse.

Participants were then randomly assigned one of four conditions: neither spouse received support, only the wife received support, only the husband received support or both spouses received support.

The researchers monitored the participants’ blood pressure and heart rate before, during and after discussions about caregiving or the lack of it.

Participants also self-reported levels of distress, closeness and support during and after the session. In a separate observation, the researchers noted that the quality of support, when provided, was generally the same for both husbands and wives during testing.

Gaining this information is important, Monin says, as it will help design more effective caregiving interventions, especially those that take into account the health conditions of both spouses and the provision of mutual health support within a marriage.

“Men and women appear to respond differently and are attuned differently to the presence or absence of emotional support about health concerns and the quality of that support,” the researchers said.

“It may be beneficial therefore, for interventions involving older couples with multiple chronic health conditions to be tailored differently to husbands and wives to make them more effective.”


Providing care to an ill-family member, particularly a spouse, is socially normative and very common.1 

Although providing care to a loved one can be a positive and rewarding experience,2there is overwhelming evidence that caregiving is also frequently financially, socially and physically taxing.1 

Caregiving has been associated with a variety of deleterious health behaviors,3,4 biomarkers,57 and outcomes,8,9 most notably a significant 63% excess mortality risk among stressed caregivers.10

Spousal caregiving is also associated with cardiovascular disease11: caregivers in the Nurses’ Health Study had an almost two-fold elevation in risk of coronary heart disease8,9 and in recent work,12 we found evidence of spousal caregiving associated with a significant elevation in risk of cardiovascular disease in a nationally representative sample of US adults.

Hypertension may help explain this connection between caregiving and CVD but its association with caregiving remains under-studied.

A few studies estimate cross-sectional associations of elevated blood pressure in caregivers.1315 

Shaw, et al. in the only longitudinal studies we know of to date, found higher levels of ADL care were associated with elevation in diastolic blood pressure16 and caregivers were at increased risk for hypertension onset17 compared to non-caregivers over 5+ years of follow-up.

However, these studies were conducted in a sample of only Alzheimer’s caregivers and its results may not be generalizable to the general population.

Furthermore, prior research has also faced a number of methodological limitations, because spousal health and social resources are likely to influence who becomes a caregiver.

In this study, we use the Health and Retirement Study (HRS), a nationally representative cohort study of Americans aged 50+, to estimate the risk of onset of hypertension associated with caring for one’s spouse and whether this risk varies by gender, race, depression, and recipient’s cognitive status.

Methods

Study Population

HRS is a longitudinal survey of a national sample of US adults aged 50+ years and their spouses. Details of the study are provided elsewhere.18,19 Enrollments occurred in 1992, 1993, or 1998 (based on respondent and spouse’s birth year) with biennial interviews (or proxy interviews for decedent participants) through 2008. Retention rates through 2008 were above 80%. HRS was approved by the University of Michigan Health Sciences Human Subjects Committee and these analyses were determined exempt by Harvard School of Public Health Office of Human Research Administration.

We included married HRS participants born 1900 to 1947 and interviewed in 2000; this was the first year caregiving assessments were consistently worded and asked with respect to spouses.

HRS included 11,474 respondents, or 5,737 couples, who were age-eligible and married/partnered with both spouses in the study in 2000. Additional exclusions were: 5,640 (49.2%) respondents who reported a prior diagnosis of hypertension in 2000, and 126 (1.1%) respondents who were missing information on basic demographic factors (age, sex, race, and ethnicity). The primary analyses were based on 5,708 individuals.

Spousal Caregiving

Spousal caregiving demand was measured at each survey administration between 2000–2006. It was assessed by the care recipient’s report of how much assistance they received with activities of daily living (ADLs; including help with getting across a room, dressing, bathing, eating, getting in and out of bed, and using the toilet) and instrumental activities of daily living (IADLs; prepare meals, shop for groceries, make telephone calls, take medications) in the last month. First, respondents were asked if they needed help with ADLs or IADLs; respondents were then asked to list everyone from whom they received care; and finally, how often they received care from each caregiver. From this, we identified spouses who were caregivers and the hours of care they provided; we use units of hours of care per week.

The measure of spousal caregiving used in this study was a dichotomized indicator of providing 14 or more hours of care per week. We chose 14 hours as a threshold to be consistent with previous studies of caregiving using these data.20,21 

As previously reported,12 we found this cut-point had construct validity: respondents who provided more than 14 hours/week of spousal care were significantly more likely to report to report their spouse “made too many demands” of them than either those who provided <14 hours/week or no care at all (details available from authors).

Any respondent who was classed as a caregiver (14+ hours/week) during both of the most recent two prior interview waves (separated by approximately two years) was classified as a “long-term caregiver.”

Incident Hypertension

Onset of hypertension between 2000 and 2008 was assessed biennially by the caregiver’s self-report of a doctor’s diagnosis of hypertension or high blood pressure. For participants who had died and those unavailable for a direct interview, interviews were conducted with proxy informants, typically spouses. The outcome variable is thus an indicator (yes/no) of the respondent’s report. In the 2006 survey waves, HRS measured blood pressure directly in a sub-sample of the total cohort. In other analyses,22 we have documented that in this older sample, self-reported hypertension has a high sensitivity (>83%) for measured hypertension defined according to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure23.

Covariates

We consider four groups of covariates that potentially influence both caregiving risk and hypertension onset and are thus plausible confounders: demographic, socioeconomic status (SES), caregiver and care recipient health risk factors.

Demographic characteristics consisted of baseline age and age-squared, race (white/non-white), Hispanic ethnicity, and gender (male/female). SES variables included years of education and household income at baseline. Caregiver health risk factors included current smoking status; body mass index in kg/m2; vigorous physical activity (dichotomized at 3+ times per week); alcohol use in the last 2 weeks (any/none); and self-reported diagnoses of diabetes.

Care recipient’s health risk factors consisted of a self-report of a doctor’s diagnosis of a memory-related problem, a summary of total number of other self-reported conditions (high blood pressure, diabetes, cancer, lung disease, heart disease, stroke, psychiatric problems, and arthritis) calculated in the RAND Corporation version of the HRS dataset24, and self-rated health (excellent/very good/good v. fair/poor). Item missingness was quite rare (<3% for all variables) and therefore we retained all observations with missing variables using a missing indicator in the weighting models.

Many of these covariates potentially mediate the pathway between caregiving and risk of hypertension—that is, they may be affected by caregiving (e.g., health risk factors) and may influence hypertension onset. We therefore used the values of all caregiver and care recipient health covariates reported in the wave prior to the caregiving assessment (e.g. 1998 covariates to control for caregiving demands in 2000) in weighting models to adjust for confounding (detailed below). All demographic and SES covariates were time-constant and used the values reported in 2000 (baseline).

Methods of Statistical Analysis

Discrete-time hazard models were used to estimate elevation in hazard of hypertension associated with high caregiving.

HRS respondents contributed person-time to the models so long as they remained alive and married and had not yet reported a diagnosis of hypertension; persons are censored after first reported incidence of hypertension. However, to avoid conflating caregiving strain with bereavement effects,25 participants were censored after dissolution of the marriage by widowhood or divorce.

Crude and adjusted hazard ratios (HRs) are presented.

Moreover, the groups of covariates defined above were added to the models sequentially, consistent with the likely temporal ordering of the confounders.

For current caregiving, 2000 was the first exposure year; for long-term caregiving, 2002 was the first exposure year, since this exposure included, by definition, a respondent’s 2000 and 2002 caregiving behavior. These analyses were completed using SAS 9.2 with PROC GENMOD with a logit link, robust variance estimates, and weights as described below.

The crude incidence of hypertension in this sample was approximately 5/100 person years, and so the odds ratio closely approximates the risk ratio; for clarity, we therefore refer to the risk ratio or relative risk throughout the results.

Inverse probability weights (IPWs) were employed to adjust for time-varying confounding.26,27

Using IPWs allows us to adjust for variables likely to be both mediators and confounders; for example, a health behavior like smoking may be affected by high caregiving and may also compromise a spouse’s ability to provide care.

All time-varying covariates were lagged by one survey wave (behind the exposure definition) to avoid bias from adjusting for mediators.

There are three IPWs calculated, one for “treatment” (caregiving), a second for study drop-out and a third weight for survival.

Thus, each observation was weighted by the product of: the inverse of the probability that individual was alive at the exposure wave; the inverse of the probability that individual (conditional on having survived) participated in the study at both exposure and outcome waves; and the inverse of the probability that the individual received the treatment he or she actually received.

Stabilized weights were calculated using previously described protocols.27

The weights were truncated at the value of 99th percentile to improve the weights’ skewed distribution and reduce influence of a small number of outliers.

To test for possible differences in the effects of caregiving across subgroups defined by sex, race, elevation in depressive symptoms for the caregiver and care recipient cognitive status, both the stratified effect estimates and a test of interaction in the pooled model are presented.

The interaction tests are on the log odds scale and therefore test for deviation from multiplicative effects.

Although much of the extant caregiving literature compares caregivers to non-caregivers, others have noted28 a better construction of the comparison for a caregiver would be a “potential” caregiver, or a non-caregiver whose spouse has care needs.

To test this idea in our sample, we conducted sensitivity analyses of our final model in a sample restricted to only spousal dyads where care needs were present at the exposure wave.

HRS used a multistage, clustered sample design. The HRS sampling weights were applied to make the population representative of the 2000 US population aged 50+ years. No difference between models that account for clustering at the household level and those that did not was found; thus, the presented models do not account for clustering.

Results

In this sample, there were 1,708 reports of new hypertension diagnoses during 31,194 person-years of follow-up (Table 1).

Over all person-years of follow-up, 3.6% (person-years=562) were classified as current caregivers, and 0.3% were long-term caregivers (person-years=101). Sample characteristics of the full sample by gender are included in Table 1.

We also present baseline sample characteristics of the full and sensitivity analysis sample (respondents whose spouses had care needs) by incident hypertension status over follow-up in Table 2.

Current high caregiving was associated with a 59% excess relative risk of hypertension diagnosis in a crude/unadjusted model (Table 3; RR=1.59, 95% CI: 1.21, 2.08). When adjusted for demographic and socioeconomic factors and recipient cognitive status and inverse probability weighted for both caregiver and recipient health status, current high caregiving was associated with a 36% excess relative risk of hypertension incidence (RR=1.36, 95% CI: 1.01, 1.83). In a crude model, long-term high caregiving was associated with nearly a two-fold increase in relative risk of hypertension onset in a crude model (RR=1.91, 95% CI: 1.08-3.35). In the fully adjusted model, long-term high caregiving was associated with more than doubling of the relative risk of new hypertension diagnosis (RR=2.29, 95% CI: 1.17, 4.49).

Interaction terms included in the models found no evidence that the relative risk of hypertension onset associated with caregiving varied significantly by caregiver race or gender or care recipient memory for either current or long-term caregivers (Table 4).

However, some sub-strata did have a significant elevation in relative risk of hypertension onset. For example, female current caregivers, white current caregivers, and current caregivers of recipient spouses without memory illnesses had significantly elevated relative risk of hypertension onset compared to the non-caregiving reference group of that stratum. Long-term caregivers of recipient spouses without memory illnesses had significant elevated relative risk of hypertension onset. Also, among men, long-term caregivers had a 3.5-fold excess risk of hypertension (RR=3.48, 95% CI: 1.56, 7.80).

In the sensitivity analyses restricted only to couples with care needs at the exposure wave, there were 256 new diagnoses of hypertension and 3,948 person years; among couples with a care recipient with long-term needs, there were 162 incidents of hypertension onset in 2,628 person-years.

The estimated relative risk of onset of hypertension associated with current caregiving was lower (RR=1.14, 95%CI: 0.77-1.68) and the CI included both the null and our estimate from the primary analyses (RR=1.36) among current caregivers. In the sample restricted to couples with care needs, the estimated risk ratio of hypertension onset associated with long-term caregiving was significant (RR=2.14, 95% CI: 1.05-4.36) and similar to the point estimate from our primary analysis (results available from authors).


Journal information: Health Psychology
Provided by Yale University

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